| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
bpf: Fix reference state management for synchronous callbacks
Currently, verifier verifies callback functions (sync and async) as if
they will be executed once, (i.e. it explores execution state as if the
function was being called once). The next insn to explore is set to
start of subprog and the exit from nested frame is handled using
curframe > 0 and prepare_func_exit. In case of async callback it uses a
customized variant of push_stack simulating a kind of branch to set up
custom state and execution context for the async callback.
While this approach is simple and works when callback really will be
executed only once, it is unsafe for all of our current helpers which
are for_each style, i.e. they execute the callback multiple times.
A callback releasing acquired references of the caller may do so
multiple times, but currently verifier sees it as one call inside the
frame, which then returns to caller. Hence, it thinks it released some
reference that the cb e.g. got access through callback_ctx (register
filled inside cb from spilled typed register on stack).
Similarly, it may see that an acquire call is unpaired inside the
callback, so the caller will copy the reference state of callback and
then will have to release the register with new ref_obj_ids. But again,
the callback may execute multiple times, but the verifier will only
account for acquired references for a single symbolic execution of the
callback, which will cause leaks.
Note that for async callback case, things are different. While currently
we have bpf_timer_set_callback which only executes it once, even for
multiple executions it would be safe, as reference state is NULL and
check_reference_leak would force program to release state before
BPF_EXIT. The state is also unaffected by analysis for the caller frame.
Hence async callback is safe.
Since we want the reference state to be accessible, e.g. for pointers
loaded from stack through callback_ctx's PTR_TO_STACK, we still have to
copy caller's reference_state to callback's bpf_func_state, but we
enforce that whatever references it adds to that reference_state has
been released before it hits BPF_EXIT. This requires introducing a new
callback_ref member in the reference state to distinguish between caller
vs callee references. Hence, check_reference_leak now errors out if it
sees we are in callback_fn and we have not released callback_ref refs.
Since there can be multiple nested callbacks, like frame 0 -> cb1 -> cb2
etc. we need to also distinguish between whether this particular ref
belongs to this callback frame or parent, and only error for our own, so
we store state->frameno (which is always non-zero for callbacks).
In short, callbacks can read parent reference_state, but cannot mutate
it, to be able to use pointers acquired by the caller. They must only
undo their changes (by releasing their own acquired_refs before
BPF_EXIT) on top of caller reference_state before returning (at which
point the caller and callback state will match anyway, so no need to
copy it back to caller). |
| In the Linux kernel, the following vulnerability has been resolved:
ftrace: Fix recursive locking direct_mutex in ftrace_modify_direct_caller
Naveen reported recursive locking of direct_mutex with sample
ftrace-direct-modify.ko:
[ 74.762406] WARNING: possible recursive locking detected
[ 74.762887] 6.0.0-rc6+ #33 Not tainted
[ 74.763216] --------------------------------------------
[ 74.763672] event-sample-fn/1084 is trying to acquire lock:
[ 74.764152] ffffffff86c9d6b0 (direct_mutex){+.+.}-{3:3}, at: \
register_ftrace_function+0x1f/0x180
[ 74.764922]
[ 74.764922] but task is already holding lock:
[ 74.765421] ffffffff86c9d6b0 (direct_mutex){+.+.}-{3:3}, at: \
modify_ftrace_direct+0x34/0x1f0
[ 74.766142]
[ 74.766142] other info that might help us debug this:
[ 74.766701] Possible unsafe locking scenario:
[ 74.766701]
[ 74.767216] CPU0
[ 74.767437] ----
[ 74.767656] lock(direct_mutex);
[ 74.767952] lock(direct_mutex);
[ 74.768245]
[ 74.768245] *** DEADLOCK ***
[ 74.768245]
[ 74.768750] May be due to missing lock nesting notation
[ 74.768750]
[ 74.769332] 1 lock held by event-sample-fn/1084:
[ 74.769731] #0: ffffffff86c9d6b0 (direct_mutex){+.+.}-{3:3}, at: \
modify_ftrace_direct+0x34/0x1f0
[ 74.770496]
[ 74.770496] stack backtrace:
[ 74.770884] CPU: 4 PID: 1084 Comm: event-sample-fn Not tainted ...
[ 74.771498] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), ...
[ 74.772474] Call Trace:
[ 74.772696] <TASK>
[ 74.772896] dump_stack_lvl+0x44/0x5b
[ 74.773223] __lock_acquire.cold.74+0xac/0x2b7
[ 74.773616] lock_acquire+0xd2/0x310
[ 74.773936] ? register_ftrace_function+0x1f/0x180
[ 74.774357] ? lock_is_held_type+0xd8/0x130
[ 74.774744] ? my_tramp2+0x11/0x11 [ftrace_direct_modify]
[ 74.775213] __mutex_lock+0x99/0x1010
[ 74.775536] ? register_ftrace_function+0x1f/0x180
[ 74.775954] ? slab_free_freelist_hook.isra.43+0x115/0x160
[ 74.776424] ? ftrace_set_hash+0x195/0x220
[ 74.776779] ? register_ftrace_function+0x1f/0x180
[ 74.777194] ? kfree+0x3e1/0x440
[ 74.777482] ? my_tramp2+0x11/0x11 [ftrace_direct_modify]
[ 74.777941] ? __schedule+0xb40/0xb40
[ 74.778258] ? register_ftrace_function+0x1f/0x180
[ 74.778672] ? my_tramp1+0xf/0xf [ftrace_direct_modify]
[ 74.779128] register_ftrace_function+0x1f/0x180
[ 74.779527] ? ftrace_set_filter_ip+0x33/0x70
[ 74.779910] ? __schedule+0xb40/0xb40
[ 74.780231] ? my_tramp1+0xf/0xf [ftrace_direct_modify]
[ 74.780678] ? my_tramp2+0x11/0x11 [ftrace_direct_modify]
[ 74.781147] ftrace_modify_direct_caller+0x5b/0x90
[ 74.781563] ? 0xffffffffa0201000
[ 74.781859] ? my_tramp1+0xf/0xf [ftrace_direct_modify]
[ 74.782309] modify_ftrace_direct+0x1b2/0x1f0
[ 74.782690] ? __schedule+0xb40/0xb40
[ 74.783014] ? simple_thread+0x2a/0xb0 [ftrace_direct_modify]
[ 74.783508] ? __schedule+0xb40/0xb40
[ 74.783832] ? my_tramp2+0x11/0x11 [ftrace_direct_modify]
[ 74.784294] simple_thread+0x76/0xb0 [ftrace_direct_modify]
[ 74.784766] kthread+0xf5/0x120
[ 74.785052] ? kthread_complete_and_exit+0x20/0x20
[ 74.785464] ret_from_fork+0x22/0x30
[ 74.785781] </TASK>
Fix this by using register_ftrace_function_nolock in
ftrace_modify_direct_caller. |
| In the Linux kernel, the following vulnerability has been resolved:
clk: ti: dra7-atl: Fix reference leak in of_dra7_atl_clk_probe
pm_runtime_get_sync() will increment pm usage counter.
Forgetting to putting operation will result in reference leak.
Add missing pm_runtime_put_sync in some error paths. |
| In the Linux kernel, the following vulnerability has been resolved:
cifs: Fix xid leak in cifs_copy_file_range()
If the file is used by swap, before return -EOPNOTSUPP, should
free the xid, otherwise, the xid will be leaked. |
| In the Linux kernel, the following vulnerability has been resolved:
platform/chrome: cros_ec_typec: zero out stale pointers
`cros_typec_get_switch_handles` allocates four pointers when obtaining
type-c switch handles. These pointers are all freed if failing to obtain
any of them; therefore, pointers in `port` become stale. The stale
pointers eventually cause use-after-free or double free in later code
paths. Zeroing out all pointer fields after freeing to eliminate these
stale pointers. |
| In the Linux kernel, the following vulnerability has been resolved:
HSI: omap_ssi: Fix refcount leak in ssi_probe
When returning or breaking early from a
for_each_available_child_of_node() loop, we need to explicitly call
of_node_put() on the child node to possibly release the node. |
| In the Linux kernel, the following vulnerability has been resolved:
ext4: fix bug_on in __es_tree_search caused by bad boot loader inode
We got a issue as fllows:
==================================================================
kernel BUG at fs/ext4/extents_status.c:203!
invalid opcode: 0000 [#1] PREEMPT SMP
CPU: 1 PID: 945 Comm: cat Not tainted 6.0.0-next-20221007-dirty #349
RIP: 0010:ext4_es_end.isra.0+0x34/0x42
RSP: 0018:ffffc9000143b768 EFLAGS: 00010203
RAX: 0000000000000000 RBX: ffff8881769cd0b8 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8fc27cf7 RDI: 00000000ffffffff
RBP: ffff8881769cd0bc R08: 0000000000000000 R09: ffffc9000143b5f8
R10: 0000000000000001 R11: 0000000000000001 R12: ffff8881769cd0a0
R13: ffff8881768e5668 R14: 00000000768e52f0 R15: 0000000000000000
FS: 00007f359f7f05c0(0000)GS:ffff88842fd00000(0000)knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f359f5a2000 CR3: 000000017130c000 CR4: 00000000000006e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
__es_tree_search.isra.0+0x6d/0xf5
ext4_es_cache_extent+0xfa/0x230
ext4_cache_extents+0xd2/0x110
ext4_find_extent+0x5d5/0x8c0
ext4_ext_map_blocks+0x9c/0x1d30
ext4_map_blocks+0x431/0xa50
ext4_mpage_readpages+0x48e/0xe40
ext4_readahead+0x47/0x50
read_pages+0x82/0x530
page_cache_ra_unbounded+0x199/0x2a0
do_page_cache_ra+0x47/0x70
page_cache_ra_order+0x242/0x400
ondemand_readahead+0x1e8/0x4b0
page_cache_sync_ra+0xf4/0x110
filemap_get_pages+0x131/0xb20
filemap_read+0xda/0x4b0
generic_file_read_iter+0x13a/0x250
ext4_file_read_iter+0x59/0x1d0
vfs_read+0x28f/0x460
ksys_read+0x73/0x160
__x64_sys_read+0x1e/0x30
do_syscall_64+0x35/0x80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
</TASK>
==================================================================
In the above issue, ioctl invokes the swap_inode_boot_loader function to
swap inode<5> and inode<12>. However, inode<5> contain incorrect imode and
disordered extents, and i_nlink is set to 1. The extents check for inode in
the ext4_iget function can be bypassed bacause 5 is EXT4_BOOT_LOADER_INO.
While links_count is set to 1, the extents are not initialized in
swap_inode_boot_loader. After the ioctl command is executed successfully,
the extents are swapped to inode<12>, in this case, run the `cat` command
to view inode<12>. And Bug_ON is triggered due to the incorrect extents.
When the boot loader inode is not initialized, its imode can be one of the
following:
1) the imode is a bad type, which is marked as bad_inode in ext4_iget and
set to S_IFREG.
2) the imode is good type but not S_IFREG.
3) the imode is S_IFREG.
The BUG_ON may be triggered by bypassing the check in cases 1 and 2.
Therefore, when the boot loader inode is bad_inode or its imode is not
S_IFREG, initialize the inode to avoid triggering the BUG. |
| In the Linux kernel, the following vulnerability has been resolved:
power: supply: cw2015: Fix potential null-ptr-deref in cw_bat_probe()
cw_bat_probe() calls create_singlethread_workqueue() and not checked the
ret value, which may return NULL. And a null-ptr-deref may happen:
cw_bat_probe()
create_singlethread_workqueue() # failed, cw_bat->wq is NULL
queue_delayed_work()
queue_delayed_work_on()
__queue_delayed_work() # warning here, but continue
__queue_work() # access wq->flags, null-ptr-deref
Check the ret value and return -ENOMEM if it is NULL. |
| In the Linux kernel, the following vulnerability has been resolved:
usb: dwc3: qcom: Fix memory leak in dwc3_qcom_interconnect_init
of_icc_get() alloc resources for path handle, we should release it when not
need anymore. Like the release in dwc3_qcom_interconnect_exit() function.
Add icc_put() in error handling to fix this. |
| In the Linux kernel, the following vulnerability has been resolved:
wifi: rsi: Fix memory leak in rsi_coex_attach()
The coex_cb needs to be freed when rsi_create_kthread() failed in
rsi_coex_attach(). |
| In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix to invalidate dcc->f2fs_issue_discard in error path
Syzbot reports a NULL pointer dereference issue as below:
__refcount_add include/linux/refcount.h:193 [inline]
__refcount_inc include/linux/refcount.h:250 [inline]
refcount_inc include/linux/refcount.h:267 [inline]
get_task_struct include/linux/sched/task.h:110 [inline]
kthread_stop+0x34/0x1c0 kernel/kthread.c:703
f2fs_stop_discard_thread+0x3c/0x5c fs/f2fs/segment.c:1638
kill_f2fs_super+0x5c/0x194 fs/f2fs/super.c:4522
deactivate_locked_super+0x70/0xe8 fs/super.c:332
deactivate_super+0xd0/0xd4 fs/super.c:363
cleanup_mnt+0x1f8/0x234 fs/namespace.c:1186
__cleanup_mnt+0x20/0x30 fs/namespace.c:1193
task_work_run+0xc4/0x14c kernel/task_work.c:177
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0x26c/0xbe0 kernel/exit.c:795
do_group_exit+0x60/0xe8 kernel/exit.c:925
__do_sys_exit_group kernel/exit.c:936 [inline]
__se_sys_exit_group kernel/exit.c:934 [inline]
__wake_up_parent+0x0/0x40 kernel/exit.c:934
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206
el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:636
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:654
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581
The root cause of this issue is in error path of f2fs_start_discard_thread(),
it missed to invalidate dcc->f2fs_issue_discard, later kthread_stop() may
access invalid pointer. |
| In the Linux kernel, the following vulnerability has been resolved:
mmc: meson-gx: fix return value check of mmc_add_host()
mmc_add_host() may return error, if we ignore its return value,
it will lead two issues:
1. The memory that allocated in mmc_alloc_host() is leaked.
2. In the remove() path, mmc_remove_host() will be called to
delete device, but it's not added yet, it will lead a kernel
crash because of null-ptr-deref in device_del().
Fix this by checking the return value and goto error path which
will call mmc_free_host(). |
| In the Linux kernel, the following vulnerability has been resolved:
drm/amdgpu/powerplay/psm: Fix memory leak in power state init
Commit 902bc65de0b3 ("drm/amdgpu/powerplay/psm: return an error in power
state init") made the power state init function return early in case of
failure to get an entry from the powerplay table, but it missed to clean up
the allocated memory for the current power state before returning. |
| In the Linux kernel, the following vulnerability has been resolved:
perf/x86/intel/uncore: Fix reference count leak in snr_uncore_mmio_map()
pci_get_device() will increase the reference count for the returned
pci_dev, so snr_uncore_get_mc_dev() will return a pci_dev with its
reference count increased. We need to call pci_dev_put() to decrease the
reference count. Let's add the missing pci_dev_put(). |
| In the Linux kernel, the following vulnerability has been resolved:
misc: pci_endpoint_test: Fix pci_endpoint_test_{copy,write,read}() panic
The dma_map_single() doesn't permit zero length mapping. It causes a follow
panic.
A panic was reported on arm64:
[ 60.137988] ------------[ cut here ]------------
[ 60.142630] kernel BUG at kernel/dma/swiotlb.c:624!
[ 60.147508] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
[ 60.152992] Modules linked in: dw_hdmi_cec crct10dif_ce simple_bridge rcar_fdp1 vsp1 rcar_vin videobuf2_vmalloc rcar_csi2 v4l
2_mem2mem videobuf2_dma_contig videobuf2_memops pci_endpoint_test videobuf2_v4l2 videobuf2_common rcar_fcp v4l2_fwnode v4l2_asyn
c videodev mc gpio_bd9571mwv max9611 pwm_rcar ccree at24 authenc libdes phy_rcar_gen3_usb3 usb_dmac display_connector pwm_bl
[ 60.186252] CPU: 0 PID: 508 Comm: pcitest Not tainted 6.0.0-rc1rpci-dev+ #237
[ 60.193387] Hardware name: Renesas Salvator-X 2nd version board based on r8a77951 (DT)
[ 60.201302] pstate: 00000005 (nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 60.208263] pc : swiotlb_tbl_map_single+0x2c0/0x590
[ 60.213149] lr : swiotlb_map+0x88/0x1f0
[ 60.216982] sp : ffff80000a883bc0
[ 60.220292] x29: ffff80000a883bc0 x28: 0000000000000000 x27: 0000000000000000
[ 60.227430] x26: 0000000000000000 x25: ffff0004c0da20d0 x24: ffff80000a1f77c0
[ 60.234567] x23: 0000000000000002 x22: 0001000040000010 x21: 000000007a000000
[ 60.241703] x20: 0000000000200000 x19: 0000000000000000 x18: 0000000000000000
[ 60.248840] x17: 0000000000000000 x16: 0000000000000000 x15: ffff0006ff7b9180
[ 60.255977] x14: ffff0006ff7b9180 x13: 0000000000000000 x12: 0000000000000000
[ 60.263113] x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
[ 60.270249] x8 : 0001000000000010 x7 : ffff0004c6754b20 x6 : 0000000000000000
[ 60.277385] x5 : ffff0004c0da2090 x4 : 0000000000000000 x3 : 0000000000000001
[ 60.284521] x2 : 0000000040000000 x1 : 0000000000000000 x0 : 0000000040000010
[ 60.291658] Call trace:
[ 60.294100] swiotlb_tbl_map_single+0x2c0/0x590
[ 60.298629] swiotlb_map+0x88/0x1f0
[ 60.302115] dma_map_page_attrs+0x188/0x230
[ 60.306299] pci_endpoint_test_ioctl+0x5e4/0xd90 [pci_endpoint_test]
[ 60.312660] __arm64_sys_ioctl+0xa8/0xf0
[ 60.316583] invoke_syscall+0x44/0x108
[ 60.320334] el0_svc_common.constprop.0+0xcc/0xf0
[ 60.325038] do_el0_svc+0x2c/0xb8
[ 60.328351] el0_svc+0x2c/0x88
[ 60.331406] el0t_64_sync_handler+0xb8/0xc0
[ 60.335587] el0t_64_sync+0x18c/0x190
[ 60.339251] Code: 52800013 d2e00414 35fff45c d503201f (d4210000)
[ 60.345344] ---[ end trace 0000000000000000 ]---
To fix it, this patch adds a checking the payload length if it is zero. |
| In the Linux kernel, the following vulnerability has been resolved:
regulator: core: Prevent integer underflow
By using a ratio of delay to poll_enabled_time that is not integer
time_remaining underflows and does not exit the loop as expected.
As delay could be derived from DT and poll_enabled_time is defined
in the driver this can easily happen.
Use a signed iterator to make sure that the loop exits once
the remaining time is negative. |
| In the Linux kernel, the following vulnerability has been resolved:
net/9p: fix double req put in p9_fd_cancelled
Syzkaller reports a KASAN issue as below:
general protection fault, probably for non-canonical address 0xfbd59c0000000021: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: maybe wild-memory-access in range [0xdead000000000108-0xdead00000000010f]
CPU: 0 PID: 5083 Comm: syz-executor.2 Not tainted 6.1.134-syzkaller-00037-g855bd1d7d838 #0
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
RIP: 0010:__list_del include/linux/list.h:114 [inline]
RIP: 0010:__list_del_entry include/linux/list.h:137 [inline]
RIP: 0010:list_del include/linux/list.h:148 [inline]
RIP: 0010:p9_fd_cancelled+0xe9/0x200 net/9p/trans_fd.c:734
Call Trace:
<TASK>
p9_client_flush+0x351/0x440 net/9p/client.c:614
p9_client_rpc+0xb6b/0xc70 net/9p/client.c:734
p9_client_version net/9p/client.c:920 [inline]
p9_client_create+0xb51/0x1240 net/9p/client.c:1027
v9fs_session_init+0x1f0/0x18f0 fs/9p/v9fs.c:408
v9fs_mount+0xba/0xcb0 fs/9p/vfs_super.c:126
legacy_get_tree+0x108/0x220 fs/fs_context.c:632
vfs_get_tree+0x8e/0x300 fs/super.c:1573
do_new_mount fs/namespace.c:3056 [inline]
path_mount+0x6a6/0x1e90 fs/namespace.c:3386
do_mount fs/namespace.c:3399 [inline]
__do_sys_mount fs/namespace.c:3607 [inline]
__se_sys_mount fs/namespace.c:3584 [inline]
__x64_sys_mount+0x283/0x300 fs/namespace.c:3584
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x35/0x80 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x6e/0xd8
This happens because of a race condition between:
- The 9p client sending an invalid flush request and later cleaning it up;
- The 9p client in p9_read_work() canceled all pending requests.
Thread 1 Thread 2
...
p9_client_create()
...
p9_fd_create()
...
p9_conn_create()
...
// start Thread 2
INIT_WORK(&m->rq, p9_read_work);
p9_read_work()
...
p9_client_rpc()
...
...
p9_conn_cancel()
...
spin_lock(&m->req_lock);
...
p9_fd_cancelled()
...
...
spin_unlock(&m->req_lock);
// status rewrite
p9_client_cb(m->client, req, REQ_STATUS_ERROR)
// first remove
list_del(&req->req_list);
...
spin_lock(&m->req_lock)
...
// second remove
list_del(&req->req_list);
spin_unlock(&m->req_lock)
...
Commit 74d6a5d56629 ("9p/trans_fd: Fix concurrency del of req_list in
p9_fd_cancelled/p9_read_work") fixes a concurrency issue in the 9p filesystem
client where the req_list could be deleted simultaneously by both
p9_read_work and p9_fd_cancelled functions, but for the case where req->status
equals REQ_STATUS_RCVD.
Update the check for req->status in p9_fd_cancelled to skip processing not
just received requests, but anything that is not SENT, as whatever
changed the state from SENT also removed the request from its list.
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
[updated the check from status == RECV || status == ERROR to status != SENT] |
| In the Linux kernel, the following vulnerability has been resolved:
pinctrl: check the return value of pinmux_ops::get_function_name()
While the API contract in docs doesn't specify it explicitly, the
generic implementation of the get_function_name() callback from struct
pinmux_ops - pinmux_generic_get_function_name() - can fail and return
NULL. This is already checked in pinmux_check_ops() so add a similar
check in pinmux_func_name_to_selector() instead of passing the returned
pointer right down to strcmp() where the NULL can get dereferenced. This
is normal operation when adding new pinfunctions. |
| In the Linux kernel, the following vulnerability has been resolved:
remoteproc: pru: Fix potential NULL pointer dereference in pru_rproc_set_ctable()
pru_rproc_set_ctable() accessed rproc->priv before the IS_ERR_OR_NULL
check, which could lead to a null pointer dereference. Move the pru
assignment, ensuring we never dereference a NULL rproc pointer. |
| In the Linux kernel, the following vulnerability has been resolved:
uio_hv_generic: Let userspace take care of interrupt mask
Remove the logic to set interrupt mask by default in uio_hv_generic
driver as the interrupt mask value is supposed to be controlled
completely by the user space. If the mask bit gets changed
by the driver, concurrently with user mode operating on the ring,
the mask bit may be set when it is supposed to be clear, and the
user-mode driver will miss an interrupt which will cause a hang.
For eg- when the driver sets inbound ring buffer interrupt mask to 1,
the host does not interrupt the guest on the UIO VMBus channel.
However, setting the mask does not prevent the host from putting a
message in the inbound ring buffer. So let’s assume that happens,
the host puts a message into the ring buffer but does not interrupt.
Subsequently, the user space code in the guest sets the inbound ring
buffer interrupt mask to 0, saying “Hey, I’m ready for interrupts”.
User space code then calls pread() to wait for an interrupt.
Then one of two things happens:
* The host never sends another message. So the pread() waits forever.
* The host does send another message. But because there’s already a
message in the ring buffer, it doesn’t generate an interrupt.
This is the correct behavior, because the host should only send an
interrupt when the inbound ring buffer transitions from empty to
not-empty. Adding an additional message to a ring buffer that is not
empty is not supposed to generate an interrupt on the guest.
Since the guest is waiting in pread() and not removing messages from
the ring buffer, the pread() waits forever.
This could be easily reproduced in hv_fcopy_uio_daemon if we delay
setting interrupt mask to 0.
Similarly if hv_uio_channel_cb() sets the interrupt_mask to 1,
there’s a race condition. Once user space empties the inbound ring
buffer, but before user space sets interrupt_mask to 0, the host could
put another message in the ring buffer but it wouldn’t interrupt.
Then the next pread() would hang.
Fix these by removing all instances where interrupt_mask is changed,
while keeping the one in set_event() unchanged to enable userspace
control the interrupt mask by writing 0/1 to /dev/uioX. |
