| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
arch_topology: Avoid use-after-free for scale_freq_data
Currently topology_scale_freq_tick() (which gets called from
scheduler_tick()) may end up using a pointer to "struct
scale_freq_data", which was previously cleared by
topology_clear_scale_freq_source(), as there is no protection in place
here. The users of topology_clear_scale_freq_source() though needs a
guarantee that the previously cleared scale_freq_data isn't used
anymore, so they can free the related resources.
Since topology_scale_freq_tick() is called from scheduler tick, we don't
want to add locking in there. Use the RCU update mechanism instead
(which is already used by the scheduler's utilization update path) to
guarantee race free updates here.
synchronize_rcu() makes sure that all RCU critical sections that started
before it is called, will finish before it returns. And so the callers
of topology_clear_scale_freq_source() don't need to worry about their
callback getting called anymore. |
| In the Linux kernel, the following vulnerability has been resolved:
net: qcom/emac: fix UAF in emac_remove
adpt is netdev private data and it cannot be
used after free_netdev() call. Using adpt after free_netdev()
can cause UAF bug. Fix it by moving free_netdev() at the end of the
function. |
| In the Linux kernel, the following vulnerability has been resolved:
net: ti: fix UAF in tlan_remove_one
priv is netdev private data and it cannot be
used after free_netdev() call. Using priv after free_netdev()
can cause UAF bug. Fix it by moving free_netdev() at the end of the
function. |
| In the Linux kernel, the following vulnerability has been resolved:
net: fddi: fix UAF in fza_probe
fp is netdev private data and it cannot be
used after free_netdev() call. Using fp after free_netdev()
can cause UAF bug. Fix it by moving free_netdev() after error message.
TURBOchannel adapter") |
| In the Linux kernel, the following vulnerability has been resolved:
bpf: Track subprog poke descriptors correctly and fix use-after-free
Subprograms are calling map_poke_track(), but on program release there is no
hook to call map_poke_untrack(). However, on program release, the aux memory
(and poke descriptor table) is freed even though we still have a reference to
it in the element list of the map aux data. When we run map_poke_run(), we then
end up accessing free'd memory, triggering KASAN in prog_array_map_poke_run():
[...]
[ 402.824689] BUG: KASAN: use-after-free in prog_array_map_poke_run+0xc2/0x34e
[ 402.824698] Read of size 4 at addr ffff8881905a7940 by task hubble-fgs/4337
[ 402.824705] CPU: 1 PID: 4337 Comm: hubble-fgs Tainted: G I 5.12.0+ #399
[ 402.824715] Call Trace:
[ 402.824719] dump_stack+0x93/0xc2
[ 402.824727] print_address_description.constprop.0+0x1a/0x140
[ 402.824736] ? prog_array_map_poke_run+0xc2/0x34e
[ 402.824740] ? prog_array_map_poke_run+0xc2/0x34e
[ 402.824744] kasan_report.cold+0x7c/0xd8
[ 402.824752] ? prog_array_map_poke_run+0xc2/0x34e
[ 402.824757] prog_array_map_poke_run+0xc2/0x34e
[ 402.824765] bpf_fd_array_map_update_elem+0x124/0x1a0
[...]
The elements concerned are walked as follows:
for (i = 0; i < elem->aux->size_poke_tab; i++) {
poke = &elem->aux->poke_tab[i];
[...]
The access to size_poke_tab is a 4 byte read, verified by checking offsets
in the KASAN dump:
[ 402.825004] The buggy address belongs to the object at ffff8881905a7800
which belongs to the cache kmalloc-1k of size 1024
[ 402.825008] The buggy address is located 320 bytes inside of
1024-byte region [ffff8881905a7800, ffff8881905a7c00)
The pahole output of bpf_prog_aux:
struct bpf_prog_aux {
[...]
/* --- cacheline 5 boundary (320 bytes) --- */
u32 size_poke_tab; /* 320 4 */
[...]
In general, subprograms do not necessarily manage their own data structures.
For example, BTF func_info and linfo are just pointers to the main program
structure. This allows reference counting and cleanup to be done on the latter
which simplifies their management a bit. The aux->poke_tab struct, however,
did not follow this logic. The initial proposed fix for this use-after-free
bug further embedded poke data tracking into the subprogram with proper
reference counting. However, Daniel and Alexei questioned why we were treating
these objects special; I agree, its unnecessary. The fix here removes the per
subprogram poke table allocation and map tracking and instead simply points
the aux->poke_tab pointer at the main programs poke table. This way, map
tracking is simplified to the main program and we do not need to manage them
per subprogram.
This also means, bpf_prog_free_deferred(), which unwinds the program reference
counting and kfrees objects, needs to ensure that we don't try to double free
the poke_tab when free'ing the subprog structures. This is easily solved by
NULL'ing the poke_tab pointer. The second detail is to ensure that per
subprogram JIT logic only does fixups on poke_tab[] entries it owns. To do
this, we add a pointer in the poke structure to point at the subprogram value
so JITs can easily check while walking the poke_tab structure if the current
entry belongs to the current program. The aux pointer is stable and therefore
suitable for such comparison. On the jit_subprogs() error path, we omit
cleaning up the poke->aux field because these are only ever referenced from
the JIT side, but on error we will never make it to the JIT, so its fine to
leave them dangling. Removing these pointers would complicate the error path
for no reason. However, we do need to untrack all poke descriptors from the
main program as otherwise they could race with the freeing of JIT memory from
the subprograms. Lastly, a748c6975dea3 ("bpf: propagate poke des
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
igc: Fix use-after-free error during reset
Cleans the next descriptor to watch (next_to_watch) when cleaning the
TX ring.
Failure to do so can cause invalid memory accesses. If igc_poll() runs
while the controller is being reset this can lead to the driver try to
free a skb that was already freed.
Log message:
[ 101.525242] refcount_t: underflow; use-after-free.
[ 101.525251] WARNING: CPU: 1 PID: 646 at lib/refcount.c:28 refcount_warn_saturate+0xab/0xf0
[ 101.525259] Modules linked in: sch_etf(E) sch_mqprio(E) rfkill(E) intel_rapl_msr(E) intel_rapl_common(E)
x86_pkg_temp_thermal(E) intel_powerclamp(E) coretemp(E) binfmt_misc(E) kvm_intel(E) kvm(E) irqbypass(E) crc32_pclmul(E)
ghash_clmulni_intel(E) aesni_intel(E) mei_wdt(E) libaes(E) crypto_simd(E) cryptd(E) glue_helper(E) snd_hda_codec_hdmi(E)
rapl(E) intel_cstate(E) snd_hda_intel(E) snd_intel_dspcfg(E) sg(E) soundwire_intel(E) intel_uncore(E) at24(E)
soundwire_generic_allocation(E) iTCO_wdt(E) soundwire_cadence(E) intel_pmc_bxt(E) serio_raw(E) snd_hda_codec(E)
iTCO_vendor_support(E) watchdog(E) snd_hda_core(E) snd_hwdep(E) snd_soc_core(E) snd_compress(E) snd_pcsp(E)
soundwire_bus(E) snd_pcm(E) evdev(E) snd_timer(E) mei_me(E) snd(E) soundcore(E) mei(E) configfs(E) ip_tables(E) x_tables(E)
autofs4(E) ext4(E) crc32c_generic(E) crc16(E) mbcache(E) jbd2(E) sd_mod(E) t10_pi(E) crc_t10dif(E) crct10dif_generic(E)
i915(E) ahci(E) libahci(E) ehci_pci(E) igb(E) xhci_pci(E) ehci_hcd(E)
[ 101.525303] drm_kms_helper(E) dca(E) xhci_hcd(E) libata(E) crct10dif_pclmul(E) cec(E) crct10dif_common(E) tsn(E) igc(E)
e1000e(E) ptp(E) i2c_i801(E) crc32c_intel(E) psmouse(E) i2c_algo_bit(E) i2c_smbus(E) scsi_mod(E) lpc_ich(E) pps_core(E)
usbcore(E) drm(E) button(E) video(E)
[ 101.525318] CPU: 1 PID: 646 Comm: irq/37-enp7s0-T Tainted: G E 5.10.30-rt37-tsn1-rt-ipipe #ipipe
[ 101.525320] Hardware name: SIEMENS AG SIMATIC IPC427D/A5E31233588, BIOS V17.02.09 03/31/2017
[ 101.525322] RIP: 0010:refcount_warn_saturate+0xab/0xf0
[ 101.525325] Code: 05 31 48 44 01 01 e8 f0 c6 42 00 0f 0b c3 80 3d 1f 48 44 01 00 75 90 48 c7 c7 78 a8 f3 a6 c6 05 0f 48
44 01 01 e8 d1 c6 42 00 <0f> 0b c3 80 3d fe 47 44 01 00 0f 85 6d ff ff ff 48 c7 c7 d0 a8 f3
[ 101.525327] RSP: 0018:ffffbdedc0917cb8 EFLAGS: 00010286
[ 101.525329] RAX: 0000000000000000 RBX: ffff98fd6becbf40 RCX: 0000000000000001
[ 101.525330] RDX: 0000000000000001 RSI: ffffffffa6f2700c RDI: 00000000ffffffff
[ 101.525332] RBP: ffff98fd6becc14c R08: ffffffffa7463d00 R09: ffffbdedc0917c50
[ 101.525333] R10: ffffffffa74c3578 R11: 0000000000000034 R12: 00000000ffffff00
[ 101.525335] R13: ffff98fd6b0b1000 R14: 0000000000000039 R15: ffff98fd6be35c40
[ 101.525337] FS: 0000000000000000(0000) GS:ffff98fd6e240000(0000) knlGS:0000000000000000
[ 101.525339] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 101.525341] CR2: 00007f34135a3a70 CR3: 0000000150210003 CR4: 00000000001706e0
[ 101.525343] Call Trace:
[ 101.525346] sock_wfree+0x9c/0xa0
[ 101.525353] unix_destruct_scm+0x7b/0xa0
[ 101.525358] skb_release_head_state+0x40/0x90
[ 101.525362] skb_release_all+0xe/0x30
[ 101.525364] napi_consume_skb+0x57/0x160
[ 101.525367] igc_poll+0xb7/0xc80 [igc]
[ 101.525376] ? sched_clock+0x5/0x10
[ 101.525381] ? sched_clock_cpu+0xe/0x100
[ 101.525385] net_rx_action+0x14c/0x410
[ 101.525388] __do_softirq+0xe9/0x2f4
[ 101.525391] __local_bh_enable_ip+0xe3/0x110
[ 101.525395] ? irq_finalize_oneshot.part.47+0xe0/0xe0
[ 101.525398] irq_forced_thread_fn+0x6a/0x80
[ 101.525401] irq_thread+0xe8/0x180
[ 101.525403] ? wake_threads_waitq+0x30/0x30
[ 101.525406] ? irq_thread_check_affinity+0xd0/0xd0
[ 101.525408] kthread+0x183/0x1a0
[ 101.525412] ? kthread_park+0x80/0x80
[ 101.525415] ret_from_fork+0x22/0x30 |
| In the Linux kernel, the following vulnerability has been resolved:
igb: Fix use-after-free error during reset
Cleans the next descriptor to watch (next_to_watch) when cleaning the
TX ring.
Failure to do so can cause invalid memory accesses. If igb_poll() runs
while the controller is reset this can lead to the driver try to free
a skb that was already freed.
(The crash is harder to reproduce with the igb driver, but the same
potential problem exists as the code is identical to igc) |
| In the Linux kernel, the following vulnerability has been resolved:
xdp, net: Fix use-after-free in bpf_xdp_link_release
The problem occurs between dev_get_by_index() and dev_xdp_attach_link().
At this point, dev_xdp_uninstall() is called. Then xdp link will not be
detached automatically when dev is released. But link->dev already
points to dev, when xdp link is released, dev will still be accessed,
but dev has been released.
dev_get_by_index() |
link->dev = dev |
| rtnl_lock()
| unregister_netdevice_many()
| dev_xdp_uninstall()
| rtnl_unlock()
rtnl_lock(); |
dev_xdp_attach_link() |
rtnl_unlock(); |
| netdev_run_todo() // dev released
bpf_xdp_link_release() |
/* access dev. |
use-after-free */ |
[ 45.966867] BUG: KASAN: use-after-free in bpf_xdp_link_release+0x3b8/0x3d0
[ 45.967619] Read of size 8 at addr ffff00000f9980c8 by task a.out/732
[ 45.968297]
[ 45.968502] CPU: 1 PID: 732 Comm: a.out Not tainted 5.13.0+ #22
[ 45.969222] Hardware name: linux,dummy-virt (DT)
[ 45.969795] Call trace:
[ 45.970106] dump_backtrace+0x0/0x4c8
[ 45.970564] show_stack+0x30/0x40
[ 45.970981] dump_stack_lvl+0x120/0x18c
[ 45.971470] print_address_description.constprop.0+0x74/0x30c
[ 45.972182] kasan_report+0x1e8/0x200
[ 45.972659] __asan_report_load8_noabort+0x2c/0x50
[ 45.973273] bpf_xdp_link_release+0x3b8/0x3d0
[ 45.973834] bpf_link_free+0xd0/0x188
[ 45.974315] bpf_link_put+0x1d0/0x218
[ 45.974790] bpf_link_release+0x3c/0x58
[ 45.975291] __fput+0x20c/0x7e8
[ 45.975706] ____fput+0x24/0x30
[ 45.976117] task_work_run+0x104/0x258
[ 45.976609] do_notify_resume+0x894/0xaf8
[ 45.977121] work_pending+0xc/0x328
[ 45.977575]
[ 45.977775] The buggy address belongs to the page:
[ 45.978369] page:fffffc00003e6600 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4f998
[ 45.979522] flags: 0x7fffe0000000000(node=0|zone=0|lastcpupid=0x3ffff)
[ 45.980349] raw: 07fffe0000000000 fffffc00003e6708 ffff0000dac3c010 0000000000000000
[ 45.981309] raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
[ 45.982259] page dumped because: kasan: bad access detected
[ 45.982948]
[ 45.983153] Memory state around the buggy address:
[ 45.983753] ffff00000f997f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[ 45.984645] ffff00000f998000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[ 45.985533] >ffff00000f998080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[ 45.986419] ^
[ 45.987112] ffff00000f998100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[ 45.988006] ffff00000f998180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
[ 45.988895] ==================================================================
[ 45.989773] Disabling lock debugging due to kernel taint
[ 45.990552] Kernel panic - not syncing: panic_on_warn set ...
[ 45.991166] CPU: 1 PID: 732 Comm: a.out Tainted: G B 5.13.0+ #22
[ 45.991929] Hardware name: linux,dummy-virt (DT)
[ 45.992448] Call trace:
[ 45.992753] dump_backtrace+0x0/0x4c8
[ 45.993208] show_stack+0x30/0x40
[ 45.993627] dump_stack_lvl+0x120/0x18c
[ 45.994113] dump_stack+0x1c/0x34
[ 45.994530] panic+0x3a4/0x7d8
[ 45.994930] end_report+0x194/0x198
[ 45.995380] kasan_report+0x134/0x200
[ 45.995850] __asan_report_load8_noabort+0x2c/0x50
[ 45.996453] bpf_xdp_link_release+0x3b8/0x3d0
[ 45.997007] bpf_link_free+0xd0/0x188
[ 45.997474] bpf_link_put+0x1d0/0x218
[ 45.997942] bpf_link_release+0x3c/0x58
[ 45.998429] __fput+0x20c/0x7e8
[ 45.998833] ____fput+0x24/0x30
[ 45.999247] task_work_run+0x104/0x258
[ 45.999731] do_notify_resume+0x894/0xaf8
[ 46.000236] work_pending
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
ALSA: seq: Fix race of snd_seq_timer_open()
The timer instance per queue is exclusive, and snd_seq_timer_open()
should have managed the concurrent accesses. It looks as if it's
checking the already existing timer instance at the beginning, but
it's not right, because there is no protection, hence any later
concurrent call of snd_seq_timer_open() may override the timer
instance easily. This may result in UAF, as the leftover timer
instance can keep running while the queue itself gets closed, as
spotted by syzkaller recently.
For avoiding the race, add a proper check at the assignment of
tmr->timeri again, and return -EBUSY if it's been already registered. |
| In the Linux kernel, the following vulnerability has been resolved:
drm: Fix use-after-free read in drm_getunique()
There is a time-of-check-to-time-of-use error in drm_getunique() due
to retrieving file_priv->master prior to locking the device's master
mutex.
An example can be seen in the crash report of the use-after-free error
found by Syzbot:
https://syzkaller.appspot.com/bug?id=148d2f1dfac64af52ffd27b661981a540724f803
In the report, the master pointer was used after being freed. This is
because another process had acquired the device's master mutex in
drm_setmaster_ioctl(), then overwrote fpriv->master in
drm_new_set_master(). The old value of fpriv->master was subsequently
freed before the mutex was unlocked.
To fix this, we lock the device's master mutex before retrieving the
pointer from from fpriv->master. This patch passes the Syzbot
reproducer test. |
| In the Linux kernel, the following vulnerability has been resolved:
bus: mhi: pci_generic: Fix possible use-after-free in mhi_pci_remove()
This driver's remove path calls del_timer(). However, that function
does not wait until the timer handler finishes. This means that the
timer handler may still be running after the driver's remove function
has finished, which would result in a use-after-free.
Fix by calling del_timer_sync(), which makes sure the timer handler
has finished, and unable to re-schedule itself. |
| In the Linux kernel, the following vulnerability has been resolved:
NFS: Fix use-after-free in nfs4_init_client()
KASAN reports a use-after-free when attempting to mount two different
exports through two different NICs that belong to the same server.
Olga was able to hit this with kernels starting somewhere between 5.7
and 5.10, but I traced the patch that introduced the clear_bit() call to
4.13. So something must have changed in the refcounting of the clp
pointer to make this call to nfs_put_client() the very last one. |
| In the Linux kernel, the following vulnerability has been resolved:
net: usb: fix possible use-after-free in smsc75xx_bind
The commit 46a8b29c6306 ("net: usb: fix memory leak in smsc75xx_bind")
fails to clean up the work scheduled in smsc75xx_reset->
smsc75xx_set_multicast, which leads to use-after-free if the work is
scheduled to start after the deallocation. In addition, this patch
also removes a dangling pointer - dev->data[0].
This patch calls cancel_work_sync to cancel the scheduled work and set
the dangling pointer to NULL. |
| In the Linux kernel, the following vulnerability has been resolved:
net: ethernet: fix potential use-after-free in ec_bhf_remove
static void ec_bhf_remove(struct pci_dev *dev)
{
...
struct ec_bhf_priv *priv = netdev_priv(net_dev);
unregister_netdev(net_dev);
free_netdev(net_dev);
pci_iounmap(dev, priv->dma_io);
pci_iounmap(dev, priv->io);
...
}
priv is netdev private data, but it is used
after free_netdev(). It can cause use-after-free when accessing priv
pointer. So, fix it by moving free_netdev() after pci_iounmap()
calls. |
| In the Linux kernel, the following vulnerability has been resolved:
can: j1939: fix Use-after-Free, hold skb ref while in use
This patch fixes a Use-after-Free found by the syzbot.
The problem is that a skb is taken from the per-session skb queue,
without incrementing the ref count. This leads to a Use-after-Free if
the skb is taken concurrently from the session queue due to a CTS. |
| In the Linux kernel, the following vulnerability has been resolved:
net: ll_temac: Make sure to free skb when it is completely used
With the skb pointer piggy-backed on the TX BD, we have a simple and
efficient way to free the skb buffer when the frame has been transmitted.
But in order to avoid freeing the skb while there are still fragments from
the skb in use, we need to piggy-back on the TX BD of the skb, not the
first.
Without this, we are doing use-after-free on the DMA side, when the first
BD of a multi TX BD packet is seen as completed in xmit_done, and the
remaining BDs are still being processed. |
| In the Linux kernel, the following vulnerability has been resolved:
net: bridge: fix vlan tunnel dst refcnt when egressing
The egress tunnel code uses dst_clone() and directly sets the result
which is wrong because the entry might have 0 refcnt or be already deleted,
causing number of problems. It also triggers the WARN_ON() in dst_hold()[1]
when a refcnt couldn't be taken. Fix it by using dst_hold_safe() and
checking if a reference was actually taken before setting the dst.
[1] dmesg WARN_ON log and following refcnt errors
WARNING: CPU: 5 PID: 38 at include/net/dst.h:230 br_handle_egress_vlan_tunnel+0x10b/0x134 [bridge]
Modules linked in: 8021q garp mrp bridge stp llc bonding ipv6 virtio_net
CPU: 5 PID: 38 Comm: ksoftirqd/5 Kdump: loaded Tainted: G W 5.13.0-rc3+ #360
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014
RIP: 0010:br_handle_egress_vlan_tunnel+0x10b/0x134 [bridge]
Code: e8 85 bc 01 e1 45 84 f6 74 90 45 31 f6 85 db 48 c7 c7 a0 02 19 a0 41 0f 94 c6 31 c9 31 d2 44 89 f6 e8 64 bc 01 e1 85 db 75 02 <0f> 0b 31 c9 31 d2 44 89 f6 48 c7 c7 70 02 19 a0 e8 4b bc 01 e1 49
RSP: 0018:ffff8881003d39e8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffffffffa01902a0
RBP: ffff8881040c6700 R08: 0000000000000000 R09: 0000000000000001
R10: 2ce93d0054fe0d00 R11: 54fe0d00000e0000 R12: ffff888109515000
R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000401
FS: 0000000000000000(0000) GS:ffff88822bf40000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f42ba70f030 CR3: 0000000109926000 CR4: 00000000000006e0
Call Trace:
br_handle_vlan+0xbc/0xca [bridge]
__br_forward+0x23/0x164 [bridge]
deliver_clone+0x41/0x48 [bridge]
br_handle_frame_finish+0x36f/0x3aa [bridge]
? skb_dst+0x2e/0x38 [bridge]
? br_handle_ingress_vlan_tunnel+0x3e/0x1c8 [bridge]
? br_handle_frame_finish+0x3aa/0x3aa [bridge]
br_handle_frame+0x2c3/0x377 [bridge]
? __skb_pull+0x33/0x51
? vlan_do_receive+0x4f/0x36a
? br_handle_frame_finish+0x3aa/0x3aa [bridge]
__netif_receive_skb_core+0x539/0x7c6
? __list_del_entry_valid+0x16e/0x1c2
__netif_receive_skb_list_core+0x6d/0xd6
netif_receive_skb_list_internal+0x1d9/0x1fa
gro_normal_list+0x22/0x3e
dev_gro_receive+0x55b/0x600
? detach_buf_split+0x58/0x140
napi_gro_receive+0x94/0x12e
virtnet_poll+0x15d/0x315 [virtio_net]
__napi_poll+0x2c/0x1c9
net_rx_action+0xe6/0x1fb
__do_softirq+0x115/0x2d8
run_ksoftirqd+0x18/0x20
smpboot_thread_fn+0x183/0x19c
? smpboot_unregister_percpu_thread+0x66/0x66
kthread+0x10a/0x10f
? kthread_mod_delayed_work+0xb6/0xb6
ret_from_fork+0x22/0x30
---[ end trace 49f61b07f775fd2b ]---
dst_release: dst:00000000c02d677a refcnt:-1
dst_release underflow |
| In the Linux kernel, the following vulnerability has been resolved:
sched/fair: Prevent dead task groups from regaining cfs_rq's
Kevin is reporting crashes which point to a use-after-free of a cfs_rq
in update_blocked_averages(). Initial debugging revealed that we've
live cfs_rq's (on_list=1) in an about to be kfree()'d task group in
free_fair_sched_group(). However, it was unclear how that can happen.
His kernel config happened to lead to a layout of struct sched_entity
that put the 'my_q' member directly into the middle of the object
which makes it incidentally overlap with SLUB's freelist pointer.
That, in combination with SLAB_FREELIST_HARDENED's freelist pointer
mangling, leads to a reliable access violation in form of a #GP which
made the UAF fail fast.
Michal seems to have run into the same issue[1]. He already correctly
diagnosed that commit a7b359fc6a37 ("sched/fair: Correctly insert
cfs_rq's to list on unthrottle") is causing the preconditions for the
UAF to happen by re-adding cfs_rq's also to task groups that have no
more running tasks, i.e. also to dead ones. His analysis, however,
misses the real root cause and it cannot be seen from the crash
backtrace only, as the real offender is tg_unthrottle_up() getting
called via sched_cfs_period_timer() via the timer interrupt at an
inconvenient time.
When unregister_fair_sched_group() unlinks all cfs_rq's from the dying
task group, it doesn't protect itself from getting interrupted. If the
timer interrupt triggers while we iterate over all CPUs or after
unregister_fair_sched_group() has finished but prior to unlinking the
task group, sched_cfs_period_timer() will execute and walk the list of
task groups, trying to unthrottle cfs_rq's, i.e. re-add them to the
dying task group. These will later -- in free_fair_sched_group() -- be
kfree()'ed while still being linked, leading to the fireworks Kevin
and Michal are seeing.
To fix this race, ensure the dying task group gets unlinked first.
However, simply switching the order of unregistering and unlinking the
task group isn't sufficient, as concurrent RCU walkers might still see
it, as can be seen below:
CPU1: CPU2:
: timer IRQ:
: do_sched_cfs_period_timer():
: :
: distribute_cfs_runtime():
: rcu_read_lock();
: :
: unthrottle_cfs_rq():
sched_offline_group(): :
: walk_tg_tree_from(…,tg_unthrottle_up,…):
list_del_rcu(&tg->list); :
(1) : list_for_each_entry_rcu(child, &parent->children, siblings)
: :
(2) list_del_rcu(&tg->siblings); :
: tg_unthrottle_up():
unregister_fair_sched_group(): struct cfs_rq *cfs_rq = tg->cfs_rq[cpu_of(rq)];
: :
list_del_leaf_cfs_rq(tg->cfs_rq[cpu]); :
: :
: if (!cfs_rq_is_decayed(cfs_rq) || cfs_rq->nr_running)
(3) : list_add_leaf_cfs_rq(cfs_rq);
: :
: :
: :
: :
:
---truncated--- |
| In the Linux kernel, the following vulnerability has been resolved:
net: dpaa2-eth: fix use-after-free in dpaa2_eth_remove
Access to netdev after free_netdev() will cause use-after-free bug.
Move debug log before free_netdev() call to avoid it. |
| In the Linux kernel, the following vulnerability has been resolved:
drm/prime: Fix use after free in mmap with drm_gem_ttm_mmap
drm_gem_ttm_mmap() drops a reference to the gem object on success. If
the gem object's refcount == 1 on entry to drm_gem_prime_mmap(), that
drop will free the gem object, and the subsequent drm_gem_object_get()
will be a UAF. Fix by grabbing a reference before calling the mmap
helper.
This issue was forseen when the reference dropping was adding in
commit 9786b65bc61ac ("drm/ttm: fix mmap refcounting"):
"For that to work properly the drm_gem_object_get() call in
drm_gem_ttm_mmap() must be moved so it happens before calling
obj->funcs->mmap(), otherwise the gem refcount would go down
to zero." |
