| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
ext4: fix invalid free tracking in ext4_xattr_move_to_block()
In ext4_xattr_move_to_block(), the value of the extended attribute
which we need to move to an external block may be allocated by
kvmalloc() if the value is stored in an external inode. So at the end
of the function the code tried to check if this was the case by
testing entry->e_value_inum.
However, at this point, the pointer to the xattr entry is no longer
valid, because it was removed from the original location where it had
been stored. So we could end up calling kvfree() on a pointer which
was not allocated by kvmalloc(); or we could also potentially leak
memory by not freeing the buffer when it should be freed. Fix this by
storing whether it should be freed in a separate variable. |
| In the Linux kernel, the following vulnerability has been resolved:
IB/mad: Don't call to function that might sleep while in atomic context
Tracepoints are not allowed to sleep, as such the following splat is
generated due to call to ib_query_pkey() in atomic context.
WARNING: CPU: 0 PID: 1888000 at kernel/trace/ring_buffer.c:2492 rb_commit+0xc1/0x220
CPU: 0 PID: 1888000 Comm: kworker/u9:0 Kdump: loaded Tainted: G OE --------- - - 4.18.0-305.3.1.el8.x86_64 #1
Hardware name: Red Hat KVM, BIOS 1.13.0-2.module_el8.3.0+555+a55c8938 04/01/2014
Workqueue: ib-comp-unb-wq ib_cq_poll_work [ib_core]
RIP: 0010:rb_commit+0xc1/0x220
RSP: 0000:ffffa8ac80f9bca0 EFLAGS: 00010202
RAX: ffff8951c7c01300 RBX: ffff8951c7c14a00 RCX: 0000000000000246
RDX: ffff8951c707c000 RSI: ffff8951c707c57c RDI: ffff8951c7c14a00
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: ffff8951c7c01300 R11: 0000000000000001 R12: 0000000000000246
R13: 0000000000000000 R14: ffffffff964c70c0 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8951fbc00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f20e8f39010 CR3: 000000002ca10005 CR4: 0000000000170ef0
Call Trace:
ring_buffer_unlock_commit+0x1d/0xa0
trace_buffer_unlock_commit_regs+0x3b/0x1b0
trace_event_buffer_commit+0x67/0x1d0
trace_event_raw_event_ib_mad_recv_done_handler+0x11c/0x160 [ib_core]
ib_mad_recv_done+0x48b/0xc10 [ib_core]
? trace_event_raw_event_cq_poll+0x6f/0xb0 [ib_core]
__ib_process_cq+0x91/0x1c0 [ib_core]
ib_cq_poll_work+0x26/0x80 [ib_core]
process_one_work+0x1a7/0x360
? create_worker+0x1a0/0x1a0
worker_thread+0x30/0x390
? create_worker+0x1a0/0x1a0
kthread+0x116/0x130
? kthread_flush_work_fn+0x10/0x10
ret_from_fork+0x35/0x40
---[ end trace 78ba8509d3830a16 ]--- |
| In the Linux kernel, the following vulnerability has been resolved:
dlm: fix plock invalid read
This patch fixes an invalid read showed by KASAN. A unlock will allocate a
"struct plock_op" and a followed send_op() will append it to a global
send_list data structure. In some cases a followed dev_read() moves it
to recv_list and dev_write() will cast it to "struct plock_xop" and access
fields which are only available in those structures. At this point an
invalid read happens by accessing those fields.
To fix this issue the "callback" field is moved to "struct plock_op" to
indicate that a cast to "plock_xop" is allowed and does the additional
"plock_xop" handling if set.
Example of the KASAN output which showed the invalid read:
[ 2064.296453] ==================================================================
[ 2064.304852] BUG: KASAN: slab-out-of-bounds in dev_write+0x52b/0x5a0 [dlm]
[ 2064.306491] Read of size 8 at addr ffff88800ef227d8 by task dlm_controld/7484
[ 2064.308168]
[ 2064.308575] CPU: 0 PID: 7484 Comm: dlm_controld Kdump: loaded Not tainted 5.14.0+ #9
[ 2064.310292] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
[ 2064.311618] Call Trace:
[ 2064.312218] dump_stack_lvl+0x56/0x7b
[ 2064.313150] print_address_description.constprop.8+0x21/0x150
[ 2064.314578] ? dev_write+0x52b/0x5a0 [dlm]
[ 2064.315610] ? dev_write+0x52b/0x5a0 [dlm]
[ 2064.316595] kasan_report.cold.14+0x7f/0x11b
[ 2064.317674] ? dev_write+0x52b/0x5a0 [dlm]
[ 2064.318687] dev_write+0x52b/0x5a0 [dlm]
[ 2064.319629] ? dev_read+0x4a0/0x4a0 [dlm]
[ 2064.320713] ? bpf_lsm_kernfs_init_security+0x10/0x10
[ 2064.321926] vfs_write+0x17e/0x930
[ 2064.322769] ? __fget_light+0x1aa/0x220
[ 2064.323753] ksys_write+0xf1/0x1c0
[ 2064.324548] ? __ia32_sys_read+0xb0/0xb0
[ 2064.325464] do_syscall_64+0x3a/0x80
[ 2064.326387] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 2064.327606] RIP: 0033:0x7f807e4ba96f
[ 2064.328470] Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 39 87 f8 ff 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 31 44 89 c7 48 89 44 24 08 e8 7c 87 f8 ff 48
[ 2064.332902] RSP: 002b:00007ffd50cfe6e0 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
[ 2064.334658] RAX: ffffffffffffffda RBX: 000055cc3886eb30 RCX: 00007f807e4ba96f
[ 2064.336275] RDX: 0000000000000040 RSI: 00007ffd50cfe7e0 RDI: 0000000000000010
[ 2064.337980] RBP: 00007ffd50cfe7e0 R08: 0000000000000000 R09: 0000000000000001
[ 2064.339560] R10: 000055cc3886eb30 R11: 0000000000000293 R12: 000055cc3886eb80
[ 2064.341237] R13: 000055cc3886eb00 R14: 000055cc3886f590 R15: 0000000000000001
[ 2064.342857]
[ 2064.343226] Allocated by task 12438:
[ 2064.344057] kasan_save_stack+0x1c/0x40
[ 2064.345079] __kasan_kmalloc+0x84/0xa0
[ 2064.345933] kmem_cache_alloc_trace+0x13b/0x220
[ 2064.346953] dlm_posix_unlock+0xec/0x720 [dlm]
[ 2064.348811] do_lock_file_wait.part.32+0xca/0x1d0
[ 2064.351070] fcntl_setlk+0x281/0xbc0
[ 2064.352879] do_fcntl+0x5e4/0xfe0
[ 2064.354657] __x64_sys_fcntl+0x11f/0x170
[ 2064.356550] do_syscall_64+0x3a/0x80
[ 2064.358259] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 2064.360745]
[ 2064.361511] Last potentially related work creation:
[ 2064.363957] kasan_save_stack+0x1c/0x40
[ 2064.365811] __kasan_record_aux_stack+0xaf/0xc0
[ 2064.368100] call_rcu+0x11b/0xf70
[ 2064.369785] dlm_process_incoming_buffer+0x47d/0xfd0 [dlm]
[ 2064.372404] receive_from_sock+0x290/0x770 [dlm]
[ 2064.374607] process_recv_sockets+0x32/0x40 [dlm]
[ 2064.377290] process_one_work+0x9a8/0x16e0
[ 2064.379357] worker_thread+0x87/0xbf0
[ 2064.381188] kthread+0x3ac/0x490
[ 2064.383460] ret_from_fork+0x22/0x30
[ 2064.385588]
[ 2064.386518] Second to last potentially related work creation:
[ 2064.389219] kasan_save_stack+0x1c/0x40
[ 2064.391043] __kasan_record_aux_stack+0xaf/0xc0
[ 2064.393303] call_rcu+0x11b/0xf70
[ 2064.394885] dlm_process_incoming_buffer+0x47d/0xfd0 [dlm]
[ 2064.397694] receive_from_sock+0x290/0x770
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
btrfs: make sure EXTENT_BUFFER_READING is cleared under refs_lock
[FALSE ALERTS]
There is a bug report that the warning inside
invalidate_and_check_btree_folios() got triggered during btrfs/298:
BTRFS info (device sdd): first mount of filesystem f9bf732a-a19b-44b9-99a7-614ddff168e2
BTRFS info (device sdd): using crc32c checksum algorithm
BTRFS error (device sdd): failed to find fsid cb2fdb42-b638-4f2f-badd-4127467ba674 when attempting to open seed devices
BTRFS error (device sdd): failed to read chunk tree: -2
------------[ cut here ]------------
WARNING: disk-io.c:3342 at invalidate_and_check_btree_folios+0x260/0x3c0 [btrfs], CPU#4: mount/125993
CPU: 4 UID: 0 PID: 125993 Comm: mount Tainted: G W OE 7.1.0-rc7-custom+ #1 PREEMPT(full)
Hardware name: QEMU KVM Virtual Machine, BIOS edk2-20250812-19.fc42 08/12/2025
Call trace:
invalidate_and_check_btree_folios+0x260/0x3c0 [btrfs] (P)
open_ctree+0x1f50/0x23b0 [btrfs]
btrfs_get_tree+0x89c/0xc48 [btrfs]
vfs_get_tree+0x30/0x110
vfs_cmd_create+0x58/0xe8
__arm64_sys_fsconfig+0x39c/0x518
invoke_syscall.constprop.0+0x48/0x120
el0_svc_common.constprop.0+0x40/0xe8
do_el0_svc+0x24/0x38
el0_svc+0x50/0x310
el0t_64_sync_handler+0xa0/0xe8
el0t_64_sync+0x198/0x1a0
---[ end trace 0000000000000000 ]---
BTRFS warning (device sdd): unable to release extent buffer 365985792 owner 3 gen 17 refs 3 flags 0x5
[CAUSE]
In that invalidate_and_check_btree_folios() we wait for the eb to finish
its read, then check if it's only held by us and the btree inode.
If not, then do a warning as it may be still held, and could cause
problems.
But there is a small window where the check can lead to false alerts:
Thread A (Read endio) | Thread B (Unmount)
----------------------------------+-------------------------------------
end_bbio_meta_read() |
| The eb has one extra ref held |
| by the reader, and has |
| EXTENT_BUFFER_READING flag set | invalidate_and_check_btree_folios()
| | |
|- clear_extent_buffer_reading() | |
| | |- wait_on_bit_io();
| | | The EXTENT_BUFFER_READING flag is
| | | cleared
| | |- if (refcount_read(eb->refs) > 2)
| | The eb is held by the read, us
| | and btree inode, thus it
| | will trigger the warning
|- free_extent_buffer() |
[FIX]
Introduce a helper, free_extent_buffer_clear_reading().
If the new parameter, @clear_reading, is set, we will hold the spinlock
at the beginning of free_extent_buffer_clear_reading() to make sure the
EXTENT_BUFFER_READING flag is cleared inside the same critical section
of decreasing refs.
Now free_extent_buffer() will just call
free_extent_buffer_clear_reading() with @clear_reading set to false, so
no behavior change.
But for end_bbio_meta_read(), it will not clear_extent_buffer_reading()
directly, but pass @clear_reading as true.
Then inside invalidate_and_check_btree_folios(), hold the refs_lock
before reading refs.
So that we eliminate the race window completely. |
| In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix slab-out-of-bounds read in ksmbd_alloc_user()
ksmbd_alloc_user() copies resp->hash_sz bytes out of the mountd IPC
login response with
user->passkey_sz = resp->hash_sz;
user->passkey = kmalloc(resp->hash_sz, KSMBD_DEFAULT_GFP);
if (user->passkey)
memcpy(user->passkey, resp->hash, resp->hash_sz);
resp->hash_sz is a __u16 supplied by the response, but resp->hash[] is
only KSMBD_REQ_MAX_HASH_SZ bytes. A malformed or malicious login
response can set hash_sz well beyond that (up to 65535), so the memcpy()
reads past the end of the response object. ipc_validate_msg() does not
bound hash_sz, so reject any response whose hash_sz exceeds the on-stack
hash[] buffer before allocating and copying.
[ 2030.238706] BUG: KASAN: slab-out-of-bounds in ksmbd_alloc_user+0x278/0x680
[ 2030.240549] Read of size 65535 at addr ffff888121bb6680 by task kworker/4:1/18611
[ 2030.242296]
[ 2030.242710] CPU: 4 UID: 0 PID: 18611 Comm: kworker/4:1 Not tainted 7.1.0-next-20260623-virtme #96 PREEMPT(lazy)
[ 2030.242732] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
[ 2030.242743] Workqueue: ksmbd-io handle_ksmbd_work
[ 2030.242763] Call Trace:
[ 2030.242769] <TASK>
[ 2030.242776] dump_stack_lvl+0xa2/0xd0
[ 2030.242794] print_address_description+0x77/0x200
[ 2030.242815] ? ksmbd_alloc_user+0x278/0x680
[ 2030.242831] print_report+0x58/0x70
[ 2030.242848] kasan_report+0x117/0x150
[ 2030.242869] ? ksmbd_alloc_user+0x278/0x680
[ 2030.242888] kasan_check_range+0x3c7/0x3f0
[ 2030.242908] ? ksmbd_alloc_user+0x278/0x680
[ 2030.242925] __asan_memcpy+0x29/0x70
[ 2030.242942] ksmbd_alloc_user+0x278/0x680
[ 2030.242960] ksmbd_login_user+0xc3/0x120
[ 2030.242978] ntlm_authenticate+0x5e6/0x1b00
[ 2030.243017] ? __pfx_ntlm_authenticate+0x10/0x10
[ 2030.243035] ? ksmbd_session_lookup+0x188/0x1d0
[ 2030.243054] ? __pfx_ksmbd_session_lookup+0x10/0x10
[ 2030.243090] ? __sanitizer_cov_trace_switch+0x7b/0x140
[ 2030.243108] smb2_sess_setup+0x1e4a/0x27b0
[ 2030.243126] ? copy_from_kernel_nofault+0x199/0x300
[ 2030.243156] ? __pfx_smb2_sess_setup+0x10/0x10
[ 2030.243173] ? get_smb2_cmd_val+0xe3/0x1c0
[ 2030.243208] handle_ksmbd_work+0x954/0x1280
[ 2030.243230] ? __pfx_handle_ksmbd_work+0x10/0x10
[ 2030.243249] ? process_scheduled_works+0xa07/0x1490
[ 2030.243270] ? process_scheduled_works+0xa07/0x1490
[ 2030.243291] process_scheduled_works+0xa70/0x1490
[ 2030.243320] ? __pfx_process_scheduled_works+0x10/0x10
[ 2030.243340] ? do_raw_spin_lock+0x130/0x300
[ 2030.243358] ? lock_is_held_type+0x7b/0x110
[ 2030.243388] worker_thread+0x932/0xe20
[ 2030.243415] kthread+0x38a/0x470
[ 2030.243431] ? __pfx_worker_thread+0x10/0x10
[ 2030.243451] ? __pfx_kthread+0x10/0x10
[ 2030.243467] ret_from_fork+0x484/0x910
[ 2030.243485] ? __pfx_ret_from_fork+0x10/0x10
[ 2030.243501] ? __switch_to+0xc77/0x12c0
[ 2030.243523] ? __pfx_kthread+0x10/0x10
[ 2030.243540] ret_from_fork_asm+0x1a/0x30
[ 2030.243564] </TASK>
[ 2030.243570]
[ 2030.290164] Allocated by task 19279:
[ 2030.290911] kasan_save_track+0x3e/0x80
[ 2030.292179] __kasan_kmalloc+0x72/0x90
[ 2030.293217] __kvmalloc_node_noprof+0x3ff/0x6b0
[ 2030.294467] handle_generic_event+0x59b/0x750
[ 2030.295345] genl_family_rcv_msg_doit+0x238/0x340
[ 2030.296553] genl_rcv_msg+0x606/0x7b0
[ 2030.297129] netlink_rcv_skb+0x22b/0x4a0
[ 2030.298500] genl_rcv+0x2d/0x40
[ 2030.299273] netlink_unicast+0x7ba/0x930
[ 2030.300019] netlink_sendmsg+0x8c3/0xb00
[ 2030.301073] __sock_sendmsg+0xec/0x140
[ 2030.301579] __sys_sendto+0x357/0x470
[ 2030.302255] __x64_sys_sendto+0xe3/0x100
[ 2030.303425] do_syscall_64+0x135/0x460
[ 2030.304763] entry_SYSCALL_64_after_hwframe+0x77/0x7f
[ 2030.305594]
[ 2030.305819] The buggy address belongs to the object at ffff888121bb6640
[ 2030.305819] which belongs to the cache kmalloc-192 of size 192
[ 2030.309595] The buggy address
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: SEV: Forcefully invalidate SNP VMSA if its backing gmem page is zapped
Wire up a gmem_invalidate_range() call for SNP VMs, and use it to force
vCPUs to reload/recheck their guest-provided VMSA if the backing gmem
page is being invalidated, e.g. is being PUNCH_HOLE'd. Use the same core
logic to handle invalidations as VMX does for the APIC-access page, as the
two concepts are nearly identical: shove the physical address of a page
into the vCPU's control structure:
1. Snapshot the invalidation sequence counter
2. Grab the pfn (from guest_memfd in this case)
3. Acquire mmu_lock for read
4. Re-request reload if retry is needed, otherwise commit the change.
Note, the re-request action in #4 is necessary as KVM's retry logic is
fuzzy, i.e. can get false positives. If the guest_memfd page has been
dropped, at some point a subsequent reload will fail to get a PFN from
guest_memfd, and KVM will fail KVM_RUN. If the retry was due to a false
positive, KVM will retry until there are no relevant MMU notifier events
(and will retry in the "outer" loop, i.e. will drop locks and resched as
needed).
Note #2! Take care to invalidate the VMSA when a relevant memslot is
DELETED or MOVED, as invalidations in response to PUNCH_HOLE are predicated
on memslot bindings (KVM doesn't know what GFN range(s) to invalidate
without a binding). And more importantly, the VMSA mapping requires a
memslot, i.e. must be invalidated if its memslots disappears, regardless of
the state of the underlying guest_memfd inode.
Failure to invalidate the vCPU's control.vmsa_pa (which is checked by
pre_sev_run()) can prevent KVM from properly freeing the page as firmware
will reject the RMPUPDATE to reclaim the page with FAIL_INUSE if the vCPU
is actively running, i.e. if VMSA page is in-use. That in turn leads to an
RMP #PF on the next use, as the page will still be assigned to the SNP VM.
SEV-SNP: RMPUPDATE failed for PFN 78d198, pg_level: 1, ret: 3
SEV-SNP: PFN 0x78d198, RMP entry: [0xfff0000000144001 - 0x000000000000000f]
CPU: 3 UID: 0 PID: 31345 Comm: sev_snp_vmsa_pu Tainted: G U O
Tainted: [U]=USER, [O]=OOT_MODULE
Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 34.86.0-102 01/25/2026
Call Trace:
<TASK>
dump_stack_lvl+0x54/0x70
rmpupdate+0x12c/0x140
rmp_make_shared+0x3b/0x60
sev_gmem_invalidate+0xe0/0x170 [kvm_amd]
delete_from_page_cache_batch+0x1d8/0x220
truncate_inode_pages_range+0x120/0x3d0
kvm_gmem_fallocate+0x19a/0x270 [kvm]
vfs_fallocate+0x1bc/0x1f0
__x64_sys_fallocate+0x48/0x70
do_syscall_64+0x10a/0x480
entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x496c7e
</TASK>
------------[ cut here ]------------
SEV: Failed to update RMP entry for PFN 0x78d198 error -14
WARNING: arch/x86/kvm/svm/sev.c:5160 at sev_gmem_invalidate+0x126/0x170 [kvm_amd], CPU#3: sev_snp_vmsa_pu/31345
CPU: 3 UID: 0 PID: 31345 Comm: sev_snp_vmsa_pu Tainted: G U O
Tainted: [U]=USER, [O]=OOT_MODULE
Hardware name: Google, Inc. Arcadia_IT_80/Arcadia_IT_80, BIOS 34.86.0-102 01/25/2026
RIP: 0010:sev_gmem_invalidate+0x12b/0x170 [kvm_amd]
Call Trace:
<TASK>
delete_from_page_cache_batch+0x1d8/0x220
truncate_inode_pages_range+0x120/0x3d0
kvm_gmem_fallocate+0x19a/0x270 [kvm]
vfs_fallocate+0x1bc/0x1f0
__x64_sys_fallocate+0x48/0x70
do_syscall_64+0x10a/0x480
entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x496c7e
</TASK>
irq event stamp: 20689
hardirqs last enabled at (20699): [<ffffffff8e76092c>] __console_unlock+0x5c/0x60
hardirqs last disabled at (20708): [<ffffffff8e760911>] __console_unlock+0x41/0x60
softirqs last enabled at (20722): [<ffffffff8e6cd74e>] __irq_exit_rcu+0x7e/0x140
softirqs last disabled at (20717): [<ffffffff8e6cd74e>] __irq_exit_rcu+0x7e/0x140
---[ end trace 0000000000000000 ]---
BUG: unable to handle page fault for address: ffff99
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: arm64: vgic-its: Don't dereference a NULL collection on ITT save
MAPC with V=0 drops ite->collection but leaves the ITE on the device's
ITT list, and vgic_its_save_ite() dereferences it unconditionally. A
guest that issues MAPD, MAPTI and then MAPC(V=0) therefore oopses the
host when the VMM issues KVM_DEV_ARM_ITS_SAVE_TABLES to migrate it.
That sequence is UNPREDICTABLE per the architecture, but KVM already
handles the resulting state in the translate, MOVI and DISCARD paths.
Save a zeroed entry, which vgic_its_restore_ite() reads back as
invalid. Skipping the ITE instead would leave the ITT slot holding
whatever is in guest memory, and restore rejects an entry naming a
collection the restored collection table does not have. |
| In the Linux kernel, the following vulnerability has been resolved:
LoongArch: KVM: Validate MSI data before routing it to EIOINTC
pch_msi_set_irq() passes e->msi.data straight into eiointc_set_irq() as
the irq number. The MSI data comes from userspace, that either via a
KVM_IRQ_ROUTING_MSI entry set with KVM_SET_GSI_ROUTING (used by irqfd
and KVM_IRQ_LINE) or directly via KVM_SIGNAL_MSI, and is never checked
against EIOINTC_IRQS.
eiointc_set_irq() uses the value with __set_bit()/__clear_bit() on the
256-bit isr bitmap, eiointc_update_irq() then indexes sw_coremap[] and
the per-cpu coreisr/sw_coreisr bitmaps with it. Therefore a data value
>= 256 reads and writes memory past the end of those arrays, i.e. any
process holding a VM fd can corrupt kernel memory beyond the allocation
of loongarch_eiointc.
Reject MSI data that doesn't fit in the EIOINTC irq space. The DMSINTC
path is unaffected as it decodes the vector from the address and masks
it. |
| In the Linux kernel, the following vulnerability has been resolved:
RISC-V: KVM: Fix PMU event info array size overflow
SBI PMU EVENT_GET_INFO stores guest-controlled num_events * sizeof(*einfo)
in a 32-bit integer. On RV64, num_events = 0x10000001 makes 0x100000010
truncate to 16. KVM then allocates one entry but loops over the original
num_events, causing out-of-bounds reads and writes. A nested guest
triggered:
BUG: KASAN: slab-out-of-bounds in kvm_riscv_vcpu_pmu_event_info+0xa4/0x142
Read of size 4 at addr ff600000074d46b0 by task init/1
Call Trace:
[<ffffffff8006471c>] kvm_riscv_vcpu_pmu_event_info+0xa4/0x142
[<ffffffff800690c0>] kvm_sbi_ext_pmu_handler+0xca/0x268
[<ffffffff8006779e>] kvm_riscv_vcpu_sbi_ecall+0xec/0x1e6
[<ffffffff8006008c>] kvm_riscv_vcpu_exit+0x48c/0x540
[<ffffffff8005ea0a>] kvm_arch_vcpu_ioctl_run+0x37e/0xc80
Allocated by task 1:
__kmalloc_noprof+0x19e/0x4b0
kvm_riscv_vcpu_pmu_event_info+0x72/0x142
kvm_sbi_ext_pmu_handler+0xca/0x268
kvm_riscv_vcpu_sbi_ecall+0xec/0x1e6
kvm_riscv_vcpu_exit+0x48c/0x540
kvm_arch_vcpu_ioctl_run+0x37e/0xc80
The buggy address is located 0 bytes to the right of
allocated 16-byte region [ff600000074d46a0, ff600000074d46b0)
Store the shared-memory size in size_t and reject multiplication overflow.
Allocate the guest-driven array with GFP_KERNEL_ACCOUNT so it is charged
to kmemcg, and use __GFP_NOWARN to suppress allocation failure warnings.
Use kvcalloc() to allow vmalloc fallback and an unsigned long loop index
to match num_events. |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: arm64: vgic: Fix race between LPI release and re-registration
Fix a potential race between decrementing an LPI's reference count and
evicting that structure from the LPI xarray.
LPI structures are maintained in the VGIC LPI xarray (dist->lpi_xa).
When the reference count of an LPI structure drops to zero,
vgic_release_lpi_locked() removes the structure from the xarray and
frees it under the xarray lock.
However, the release of an LPI can race with a concurrent LPI
re-registration with the same INTID via vgic_add_lpi() on another CPU,
since the reference count drop and the xarray eviction are not performed
in a single atomic step. This can happen e.g. if the guest issues a
DISCARD while the LPI is still referenced from a vCPU's active-pending
list (ap_list), and the same INTID is re-mapped via MAPTI.
Particularly, vgic_release_lpi_locked() is called from two distinct
paths: direct release via vgic_put_irq(), and deferred release via
vgic_release_deleted_lpis(). During direct release, the issue can result
in deleting a newly registered LPI from the xarray:
CPU0 (Releasing LPI) CPU1 (Adding new LPI)
==================== =====================
vgic_put_irq()
__vgic_put_irq()
refcount_dec_and_test()
vgic_add_lpi()
xa_lock_irqsave()
old_irq = xa_load(.., intid)
vgic_try_get_irq_ref(old_irq) == false
new IRQ inserted --> __xa_store(.., intid, ..)
xa_unlock_irqrestore()
xa_lock_irqsave();
vgic_release_lpi_locked()
__xa_erase(.., irq->intid) <-- BUG: new IRQ is erased
kfree_rcu(old_irq)
During the deferred release path, the old IRQ can be leaked:
CPU0 (Releasing LPI) CPU1 (Adding new LPI)
==================== =====================
vgic_put_irq_norelease()
__vgic_put_irq()
refcount_dec_and_test()
irq->pending_release = true
vgic_add_lpi()
xa_lock_irqsave()
old_irq = xa_load(.., intid)
vgic_try_get_irq_ref(oldirq) == false
BUG: old IRQ overwritten --> __xa_store(.., intid, ..)
xa_unlock_irqrestore()
vgic_release_deleted_lpis()
xa_lock_irqsave()
xa_for_each() { .. } <-- old IRQ with pending_release = true
is gone, so it cannot be released
To fix the direct release path, move the reference count drop inside
the xarray lock, making sure that vgic_add_lpi() never encounters the
to-be-released LPI.
In the deferred release path, the refcount drop must happen under a raw
spinlock, so the xarray lock cannot be grabbed, and the same solution
does not work. Instead, update vgic_add_lpi(), so that if it evicts
an LPI from the xarray, it takes on the responsibility of freeing it.
Consequently, an LPI may now be freed concurrently after a deferred
release drops the refcount, so accessing the pending_release field is no
longer safe from use-after-free. Delete all uses of the flag, and update
vgic_release_deleted_lpis() to identify orphaned LPIs purely based on
their refcount. |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: guest_memfd: Treat memslot binding offset+size as unsigned values
When binding a memslot to a guest_memfd file, treat the offset and size as
unsigned values to fix a bug where the sum of the two can result in a false
negative when checking for overflow against the size of the file. Passing
unsigned values also avoids relying on somewhat obscure checks in other
flows for safety, and tracks the offset and size as they are intended to be
tracked, as unsigned values.
On 64-bit kernels, the number of pages a memslot contains and thus the size
(and offset) of its guest_memfd binding are unsigned 64-bit values. Taking
the offset+size as an loff_t instead of a uoff_t inadvertently converts
the unsigned value to a signed value if the offset and/or size is massive.
Locally storing the offset and size as signed values is benign in and of
itself (though even that is *extremely* difficult to discern), but
operating on their sum is not.
For the offset, KVM explicitly checks against a negative value, which might
seem like a bug as KVM could incorrectly reject a legitimate binding, but
that's not actually the case as KVM_CREATE_GUEST_MEMFD takes a signed value
for its size, i.e. a would-be-negative offset is also greater than the
maximum possible size of any guest_memfd file.
Regarding the size, while KVM lacks an explicit check for a negative value,
i.e. seemingly has a flawed overflow check, KVM restricts the number of
pages in a single memslot to the largest positive signed 32-bit value:
if (id < KVM_USER_MEM_SLOTS &&
(mem->memory_size >> PAGE_SHIFT) > KVM_MEM_MAX_NR_PAGES)
return -EINVAL;
and so that maximum "size" will ever be is 0x7fffffff000.
The sum of the two is, however, problematic. While the size is restricted
by KVM's memslot logic, the offset is not, i.e. the offset is completely
unchecked until the "offset + size > i_size_read(inode)" check. If the
offset is the (nearly) largest possible _positive_ value, then adding size
to the offset can result in a signed, negative 64-bit value. When compared
against the size of the file (guaranteed to be positive), the negative sum
is always smaller, and KVM incorrectly allows the absurd offset.
Opportunistically add missing includes in kvm_mm.h (instead of relying on
its parents). |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: arm64: Correctly cap ZCR_EL2 provided by a guest hypervisor
ZCR_EL2 can be updated by a VHE guest hypervisor either using ZCR_EL2
(which traps) or ZCR_EL1 (which does not trap). KVM handles both in
different way:
- on ZCR_EL2 trap, ZCR_EL2.LEN is immediately capped at the VM's own
VL limit. This has the potential to break existing SW that relies
on the full LEN field to be stateful.
- on ZCR_EL1 access, we do absolutely nothing.
On restoring the SVE context for an L2 guest, we directly restore the
guest hypervisor's view of ZCR_EL2 into the physical ZCR_EL2. If the
guest's view of the register was updated using the ZCR_EL2 accessor,
the value has already been sanitised (with the caveat mentioned above).
But if the guest used ZCR_EL1, the raw value is written into the HW,
and the L2 guest can now access VLs that it shouldn't.
Fix all the above by moving the VL capping to the restore points,
ensuring that:
- the HW is always programmed with a capped value, irrespective of
the accessor being used,
- the ZCR_EL2.LEN field is always completely stateful, irrespective
of the accessor being used.
Additionally, move ZCR_EL2 to be a sanitised register, ensuring that
only the LEN field is actually stateful. This requires some creative
construction of the RES0 mask, as the sysreg generation script does
not yet generate RAZ/WI fields.
[maz: rewrote commit message, tidy up access_zcr_el2()] |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: nSVM: Triple fault if restore host CR3 fails on nested #VMEXIT
If loading L1's CR3 fails on a nested #VMEXIT, nested_svm_vmexit()
returns an error code that is ignored by most callers, and continues to
run L1 with corrupted state. A sane recovery is not possible in this
case, and HW behavior is to cause a shutdown. Inject a triple fault
instead, and do not return early from nested_svm_vmexit(). Continue
cleaning up the vCPU state (e.g. clear pending exceptions), to handle
the failure as gracefully as possible.
From the APM:
Upon #VMEXIT, the processor performs the following actions in order to
return to the host execution context:
...
if (illegal host state loaded, or exception while loading host state)
shutdown
else
execute first host instruction following the VMRUN
Remove the return value of nested_svm_vmexit(), which is mostly
unchecked anyway. |
| In the Linux kernel, the following vulnerability has been resolved:
btrfs: do not ASSERT() when the fs flips RO inside btrfs_repair_io_failure()
[BUG]
There is a bug report that when btrfs hits ENOSPC error in a critical
path, btrfs flips RO (this part is expected, although the ENOSPC bug
still needs to be addressed).
The problem is after the RO flip, if there is a read repair pending, we
can hit the ASSERT() inside btrfs_repair_io_failure() like the following:
BTRFS info (device vdc): relocating block group 30408704 flags metadata|raid1
------------[ cut here ]------------
BTRFS: Transaction aborted (error -28)
WARNING: fs/btrfs/extent-tree.c:3235 at __btrfs_free_extent.isra.0+0x453/0xfd0, CPU#1: btrfs/383844
Modules linked in: kvm_intel kvm irqbypass
[...]
---[ end trace 0000000000000000 ]---
BTRFS info (device vdc state EA): 2 enospc errors during balance
BTRFS info (device vdc state EA): balance: ended with status: -30
BTRFS error (device vdc state EA): parent transid verify failed on logical 30556160 mirror 2 wanted 8 found 6
BTRFS error (device vdc state EA): bdev /dev/nvme0n1 errs: wr 0, rd 0, flush 0, corrupt 10, gen 0
[...]
assertion failed: !(fs_info->sb->s_flags & SB_RDONLY) :: 0, in fs/btrfs/bio.c:938
------------[ cut here ]------------
assertion failed: !(fs_info->sb->s_flags & SB_RDONLY) :: 0, in fs/btrfs/bio.c:938
kernel BUG at fs/btrfs/bio.c:938!
Oops: invalid opcode: 0000 [#1] SMP NOPTI
CPU: 0 UID: 0 PID: 868 Comm: kworker/u8:13 Tainted: G W N 6.19.0-rc6+ #4788 PREEMPT(full)
Tainted: [W]=WARN, [N]=TEST
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.17.0-0-gb52ca86e094d-prebuilt.qemu.org 04/01/2014
Workqueue: btrfs-endio simple_end_io_work
RIP: 0010:btrfs_repair_io_failure.cold+0xb2/0x120
RSP: 0000:ffffc90001d2bcf0 EFLAGS: 00010246
RAX: 0000000000000051 RBX: 0000000000001000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8305cf42 RDI: 00000000ffffffff
RBP: 0000000000000002 R08: 00000000fffeffff R09: ffffffff837fa988
R10: ffffffff8327a9e0 R11: 6f69747265737361 R12: ffff88813018d310
R13: ffff888168b8a000 R14: ffffc90001d2bd90 R15: ffff88810a169000
FS: 0000000000000000(0000) GS:ffff8885e752c000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
------------[ cut here ]------------
[CAUSE]
The cause of -ENOSPC error during the test case btrfs/124 is still
unknown, although it's known that we still have cases where metadata can
be over-committed but can not be fulfilled correctly, thus if we hit
such ENOSPC error inside a critical path, we have no choice but abort
the current transaction.
This will mark the fs read-only.
The problem is inside the btrfs_repair_io_failure() path that we require
the fs not to be mount read-only. This is normally fine, but if we are
doing a read-repair meanwhile the fs flips RO due to a critical error,
we can enter btrfs_repair_io_failure() with super block set to
read-only, thus triggering the above crash.
[FIX]
Just replace the ASSERT() with a proper return if the fs is already
read-only. |
| In the Linux kernel, the following vulnerability has been resolved:
agp/amd64: Fix broken error propagation in agp_amd64_probe()
A NULL pointer dereference was observed in the AMD64 AGP driver when
running in a virtualized environment (e.g. qemu/kvm) without a physical
AMD northbridge. The crash occurs in amd64_fetch_size() when attempting
to dereference the pointer returned by node_to_amd_nb(0).
The root cause of this crash is broken error propagation in
agp_amd64_probe(): When no AMD northbridges are found, cache_nbs()
correctly returns -ENODEV. However, the probe function erroneously
checks the return value against exactly -1, rather than < 0.
As a result, the hardware absence error is masked, allowing the driver
to improperly proceed with initialization. It eventually calls
agp_add_bridge(), which invokes amd64_fetch_size(). Since the hardware
does not exist, node_to_amd_nb(0) returns NULL, leading to a General
Protection Fault (GPF) when accessing its ->misc member.
Fix the issue by correcting the error check in agp_amd64_probe() to
abort properly when cache_nbs() returns any negative error code. This
prevents the driver from erroneously proceeding without hardware, thereby
avoiding the subsequent NULL pointer dereference at its source. |
| In the Linux kernel, the following vulnerability has been resolved:
net/sched: cls_fw: fix NULL dereference of "old" filters before change()
Like pointed out by Sashiko [1], since commit ed76f5edccc9 ("net: sched:
protect filter_chain list with filter_chain_lock mutex") TC filters are
added to a shared block and published to datapath before their ->change()
function is called. This is a problem for cls_fw: an invalid filter
created with the "old" method can still classify some packets before it
is destroyed by the validation logic added by Xiang.
Therefore, insisting with repeated runs of the following script:
# ip link add dev crash0 type dummy
# ip link set dev crash0 up
# mausezahn crash0 -c 100000 -P 10 \
> -A 4.3.2.1 -B 1.2.3.4 -t udp "dp=1234" -q &
# sleep 1
# tc qdisc add dev crash0 egress_block 1 clsact
# tc filter add block 1 protocol ip prio 1 matchall \
> action skbedit mark 65536 continue
# tc filter add block 1 protocol ip prio 2 fw
# ip link del dev crash0
can still make fw_classify() hit the WARN_ON() in [2]:
WARNING: ./include/net/pkt_cls.h:88 at fw_classify+0x244/0x250 [cls_fw], CPU#18: mausezahn/1399
Modules linked in: cls_fw(E) act_skbedit(E)
CPU: 18 UID: 0 PID: 1399 Comm: mausezahn Tainted: G E 7.0.0-rc6-virtme #17 PREEMPT(full)
Tainted: [E]=UNSIGNED_MODULE
Hardware name: Red Hat KVM, BIOS 1.16.3-2.el9 04/01/2014
RIP: 0010:fw_classify+0x244/0x250 [cls_fw]
Code: 5c 49 c7 45 00 00 00 00 00 41 5d 41 5e 41 5f 5d c3 cc cc cc cc 5b b8 ff ff ff ff 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc 90 <0f> 0b 90 eb a0 0f 1f 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffd1b7026bf8a8 EFLAGS: 00010202
RAX: ffff8c5ac9c60800 RBX: ffff8c5ac99322c0 RCX: 0000000000000004
RDX: 0000000000000001 RSI: ffff8c5b74d7a000 RDI: ffff8c5ac8284f40
RBP: ffffd1b7026bf8d0 R08: 0000000000000000 R09: ffffd1b7026bf9b0
R10: 00000000ffffffff R11: 0000000000000000 R12: 0000000000010000
R13: ffffd1b7026bf930 R14: ffff8c5ac8284f40 R15: 0000000000000000
FS: 00007fca40c37740(0000) GS:ffff8c5b74d7a000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fca40e822a0 CR3: 0000000005ca0001 CR4: 0000000000172ef0
Call Trace:
<TASK>
tcf_classify+0x17d/0x5c0
tc_run+0x9d/0x150
__dev_queue_xmit+0x2ab/0x14d0
ip_finish_output2+0x340/0x8f0
ip_output+0xa4/0x250
raw_sendmsg+0x147d/0x14b0
__sys_sendto+0x1cc/0x1f0
__x64_sys_sendto+0x24/0x30
do_syscall_64+0x126/0xf80
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fca40e822ba
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb b8 0f 1f 00 f3 0f 1e fa 41 89 ca 64 8b 04 25 18 00 00 00 85 c0 75 15 b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 7e c3 0f 1f 44 00 00 41 54 48 83 ec 30 44 89
RSP: 002b:00007ffc248a42c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 000055ef233289d0 RCX: 00007fca40e822ba
RDX: 000000000000001e RSI: 000055ef23328c30 RDI: 0000000000000003
RBP: 000055ef233289d0 R08: 00007ffc248a42d0 R09: 0000000000000010
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000000001e
R13: 00000000000186a0 R14: 0000000000000000 R15: 00007fca41043000
</TASK>
irq event stamp: 1045778
hardirqs last enabled at (1045784): [<ffffffff864ec042>] __up_console_sem+0x52/0x60
hardirqs last disabled at (1045789): [<ffffffff864ec027>] __up_console_sem+0x37/0x60
softirqs last enabled at (1045426): [<ffffffff874d48c7>] __alloc_skb+0x207/0x260
softirqs last disabled at (1045434): [<ffffffff874fe8f8>] __dev_queue_xmit+0x78/0x14d0
Then, because of the value in the packet's mark, dereference on 'q->handle'
with NULL 'q' occurs:
BUG: kernel NULL pointer dereference, address: 0000000000000038
[...]
RIP: 0010:fw_classify+0x1fe/0x250 [cls_fw]
[...]
Skip "old-style" classification on shared blocks, so that the NULL
dereference is fixed and WARN_ON() is not hit anymore in the short
lifetime of invalid cls_fw "old-style" filters.
[1] https://sashiko.dev/#/patchset/2
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix out-of-bounds write in smb2_get_ea() EA alignment
smb2_get_ea() applies 4-byte alignment padding via memset() after
writing each EA entry. The bounds check on buf_free_len is performed
before the value memcpy, but the alignment memset fires unconditionally
afterward with no check on remaining space.
When the EA value exactly fills the remaining buffer (buf_free_len == 0
after value subtraction), the alignment memset writes 1-3 NUL bytes
past the buf_free_len boundary. In compound requests where the response
buffer is shared across commands, the first command (e.g., READ) can
consume most of the buffer, leaving a tight remainder for the QUERY_INFO
EA response. The alignment memset then overwrites past the physical
kvmalloc allocation into adjacent kernel heap memory.
Add a bounds check before the alignment memset to ensure buf_free_len
can accommodate the padding bytes.
This is the same bug pattern fixed by commit beef2634f81f ("ksmbd: fix
potencial OOB in get_file_all_info() for compound requests") and
commit fda9522ed6af ("ksmbd: fix OOB write in QUERY_INFO for compound
requests"), both of which added bounds checks before unconditional
writes in QUERY_INFO response handlers. |
| In the Linux kernel, the following vulnerability has been resolved:
x86/fpu: Clear XSTATE_BV[i] in guest XSAVE state whenever XFD[i]=1
When loading guest XSAVE state via KVM_SET_XSAVE, and when updating XFD in
response to a guest WRMSR, clear XFD-disabled features in the saved (or to
be restored) XSTATE_BV to ensure KVM doesn't attempt to load state for
features that are disabled via the guest's XFD. Because the kernel
executes XRSTOR with the guest's XFD, saving XSTATE_BV[i]=1 with XFD[i]=1
will cause XRSTOR to #NM and panic the kernel.
E.g. if fpu_update_guest_xfd() sets XFD without clearing XSTATE_BV:
------------[ cut here ]------------
WARNING: arch/x86/kernel/traps.c:1524 at exc_device_not_available+0x101/0x110, CPU#29: amx_test/848
Modules linked in: kvm_intel kvm irqbypass
CPU: 29 UID: 1000 PID: 848 Comm: amx_test Not tainted 6.19.0-rc2-ffa07f7fd437-x86_amx_nm_xfd_non_init-vm #171 NONE
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:exc_device_not_available+0x101/0x110
Call Trace:
<TASK>
asm_exc_device_not_available+0x1a/0x20
RIP: 0010:restore_fpregs_from_fpstate+0x36/0x90
switch_fpu_return+0x4a/0xb0
kvm_arch_vcpu_ioctl_run+0x1245/0x1e40 [kvm]
kvm_vcpu_ioctl+0x2c3/0x8f0 [kvm]
__x64_sys_ioctl+0x8f/0xd0
do_syscall_64+0x62/0x940
entry_SYSCALL_64_after_hwframe+0x4b/0x53
</TASK>
---[ end trace 0000000000000000 ]---
This can happen if the guest executes WRMSR(MSR_IA32_XFD) to set XFD[18] = 1,
and a host IRQ triggers kernel_fpu_begin() prior to the vmexit handler's
call to fpu_update_guest_xfd().
and if userspace stuffs XSTATE_BV[i]=1 via KVM_SET_XSAVE:
------------[ cut here ]------------
WARNING: arch/x86/kernel/traps.c:1524 at exc_device_not_available+0x101/0x110, CPU#14: amx_test/867
Modules linked in: kvm_intel kvm irqbypass
CPU: 14 UID: 1000 PID: 867 Comm: amx_test Not tainted 6.19.0-rc2-2dace9faccd6-x86_amx_nm_xfd_non_init-vm #168 NONE
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
RIP: 0010:exc_device_not_available+0x101/0x110
Call Trace:
<TASK>
asm_exc_device_not_available+0x1a/0x20
RIP: 0010:restore_fpregs_from_fpstate+0x36/0x90
fpu_swap_kvm_fpstate+0x6b/0x120
kvm_load_guest_fpu+0x30/0x80 [kvm]
kvm_arch_vcpu_ioctl_run+0x85/0x1e40 [kvm]
kvm_vcpu_ioctl+0x2c3/0x8f0 [kvm]
__x64_sys_ioctl+0x8f/0xd0
do_syscall_64+0x62/0x940
entry_SYSCALL_64_after_hwframe+0x4b/0x53
</TASK>
---[ end trace 0000000000000000 ]---
The new behavior is consistent with the AMX architecture. Per Intel's SDM,
XSAVE saves XSTATE_BV as '0' for components that are disabled via XFD
(and non-compacted XSAVE saves the initial configuration of the state
component):
If XSAVE, XSAVEC, XSAVEOPT, or XSAVES is saving the state component i,
the instruction does not generate #NM when XCR0[i] = IA32_XFD[i] = 1;
instead, it operates as if XINUSE[i] = 0 (and the state component was
in its initial state): it saves bit i of XSTATE_BV field of the XSAVE
header as 0; in addition, XSAVE saves the initial configuration of the
state component (the other instructions do not save state component i).
Alternatively, KVM could always do XRSTOR with XFD=0, e.g. by using
a constant XFD based on the set of enabled features when XSAVEing for
a struct fpu_guest. However, having XSTATE_BV[i]=1 for XFD-disabled
features can only happen in the above interrupt case, or in similar
scenarios involving preemption on preemptible kernels, because
fpu_swap_kvm_fpstate()'s call to save_fpregs_to_fpstate() saves the
outgoing FPU state with the current XFD; and that is (on all but the
first WRMSR to XFD) the guest XFD.
Therefore, XFD can only go out of sync with XSTATE_BV in the above
interrupt case, or in similar scenarios involving preemption on
preemptible kernels, and it we can consider it (de facto) part of KVM
ABI that KVM_GET_XSAVE returns XSTATE_BV[i]=0 for XFD-disabled features.
[Move clea
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
KVM: x86: Fix VM hard lockup after prolonged inactivity with periodic HV timer
When advancing the target expiration for the guest's APIC timer in periodic
mode, set the expiration to "now" if the target expiration is in the past
(similar to what is done in update_target_expiration()). Blindly adding
the period to the previous target expiration can result in KVM generating
a practically unbounded number of hrtimer IRQs due to programming an
expired timer over and over. In extreme scenarios, e.g. if userspace
pauses/suspends a VM for an extended duration, this can even cause hard
lockups in the host.
Currently, the bug only affects Intel CPUs when using the hypervisor timer
(HV timer), a.k.a. the VMX preemption timer. Unlike the software timer,
a.k.a. hrtimer, which KVM keeps running even on exits to userspace, the
HV timer only runs while the guest is active. As a result, if the vCPU
does not run for an extended duration, there will be a huge gap between
the target expiration and the current time the vCPU resumes running.
Because the target expiration is incremented by only one period on each
timer expiration, this leads to a series of timer expirations occurring
rapidly after the vCPU/VM resumes.
More critically, when the vCPU first triggers a periodic HV timer
expiration after resuming, advancing the expiration by only one period
will result in a target expiration in the past. As a result, the delta
may be calculated as a negative value. When the delta is converted into
an absolute value (tscdeadline is an unsigned u64), the resulting value
can overflow what the HV timer is capable of programming. I.e. the large
value will exceed the VMX Preemption Timer's maximum bit width of
cpu_preemption_timer_multi + 32, and thus cause KVM to switch from the
HV timer to the software timer (hrtimers).
After switching to the software timer, periodic timer expiration callbacks
may be executed consecutively within a single clock interrupt handler,
because hrtimers honors KVM's request for an expiration in the past and
immediately re-invokes KVM's callback after reprogramming. And because
the interrupt handler runs with IRQs disabled, restarting KVM's hrtimer
over and over until the target expiration is advanced to "now" can result
in a hard lockup.
E.g. the following hard lockup was triggered in the host when running a
Windows VM (only relevant because it used the APIC timer in periodic mode)
after resuming the VM from a long suspend (in the host).
NMI watchdog: Watchdog detected hard LOCKUP on cpu 45
...
RIP: 0010:advance_periodic_target_expiration+0x4d/0x80 [kvm]
...
RSP: 0018:ff4f88f5d98d8ef0 EFLAGS: 00000046
RAX: fff0103f91be678e RBX: fff0103f91be678e RCX: 00843a7d9e127bcc
RDX: 0000000000000002 RSI: 0052ca4003697505 RDI: ff440d5bfbdbd500
RBP: ff440d5956f99200 R08: ff2ff2a42deb6a84 R09: 000000000002a6c0
R10: 0122d794016332b3 R11: 0000000000000000 R12: ff440db1af39cfc0
R13: ff440db1af39cfc0 R14: ffffffffc0d4a560 R15: ff440db1af39d0f8
FS: 00007f04a6ffd700(0000) GS:ff440db1af380000(0000) knlGS:000000e38a3b8000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000d5651feff8 CR3: 000000684e038002 CR4: 0000000000773ee0
PKRU: 55555554
Call Trace:
<IRQ>
apic_timer_fn+0x31/0x50 [kvm]
__hrtimer_run_queues+0x100/0x280
hrtimer_interrupt+0x100/0x210
? ttwu_do_wakeup+0x19/0x160
smp_apic_timer_interrupt+0x6a/0x130
apic_timer_interrupt+0xf/0x20
</IRQ>
Moreover, if the suspend duration of the virtual machine is not long enough
to trigger a hard lockup in this scenario, since commit 98c25ead5eda
("KVM: VMX: Move preemption timer <=> hrtimer dance to common x86"), KVM
will continue using the software timer until the guest reprograms the APIC
timer in some way. Since the periodic timer does not require frequent APIC
timer register programming, the guest may continue to use the software
timer in
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
x86/vmscape: Add conditional IBPB mitigation
VMSCAPE is a vulnerability that exploits insufficient branch predictor
isolation between a guest and a userspace hypervisor (like QEMU). Existing
mitigations already protect kernel/KVM from a malicious guest. Userspace
can additionally be protected by flushing the branch predictors after a
VMexit.
Since it is the userspace that consumes the poisoned branch predictors,
conditionally issue an IBPB after a VMexit and before returning to
userspace. Workloads that frequently switch between hypervisor and
userspace will incur the most overhead from the new IBPB.
This new IBPB is not integrated with the existing IBPB sites. For
instance, a task can use the existing speculation control prctl() to
get an IBPB at context switch time. With this implementation, the
IBPB is doubled up: one at context switch and another before running
userspace.
The intent is to integrate and optimize these cases post-embargo.
[ dhansen: elaborate on suboptimal IBPB solution ] |
