| CVE |
Vendors |
Products |
Updated |
CVSS v3.1 |
| In the Linux kernel, the following vulnerability has been resolved:
nvmet: fix a use-after-free
Fix the following use-after-free complaint triggered by blktests nvme/004:
BUG: KASAN: user-memory-access in blk_mq_complete_request_remote+0xac/0x350
Read of size 4 at addr 0000607bd1835943 by task kworker/13:1/460
Workqueue: nvmet-wq nvme_loop_execute_work [nvme_loop]
Call Trace:
show_stack+0x52/0x58
dump_stack_lvl+0x49/0x5e
print_report.cold+0x36/0x1e2
kasan_report+0xb9/0xf0
__asan_load4+0x6b/0x80
blk_mq_complete_request_remote+0xac/0x350
nvme_loop_queue_response+0x1df/0x275 [nvme_loop]
__nvmet_req_complete+0x132/0x4f0 [nvmet]
nvmet_req_complete+0x15/0x40 [nvmet]
nvmet_execute_io_connect+0x18a/0x1f0 [nvmet]
nvme_loop_execute_work+0x20/0x30 [nvme_loop]
process_one_work+0x56e/0xa70
worker_thread+0x2d1/0x640
kthread+0x183/0x1c0
ret_from_fork+0x1f/0x30 |
| In the Linux kernel, the following vulnerability has been resolved:
nvme-tcp: fix UAF when detecting digest errors
We should also bail from the io_work loop when we set rd_enabled to true,
so we don't attempt to read data from the socket when the TCP stream is
already out-of-sync or corrupted. |
| In the Linux kernel, the following vulnerability has been resolved:
erofs: fix pcluster use-after-free on UP platforms
During stress testing with CONFIG_SMP disabled, KASAN reports as below:
==================================================================
BUG: KASAN: use-after-free in __mutex_lock+0xe5/0xc30
Read of size 8 at addr ffff8881094223f8 by task stress/7789
CPU: 0 PID: 7789 Comm: stress Not tainted 6.0.0-rc1-00002-g0d53d2e882f9 #3
Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
Call Trace:
<TASK>
..
__mutex_lock+0xe5/0xc30
..
z_erofs_do_read_page+0x8ce/0x1560
..
z_erofs_readahead+0x31c/0x580
..
Freed by task 7787
kasan_save_stack+0x1e/0x40
kasan_set_track+0x20/0x30
kasan_set_free_info+0x20/0x40
__kasan_slab_free+0x10c/0x190
kmem_cache_free+0xed/0x380
rcu_core+0x3d5/0xc90
__do_softirq+0x12d/0x389
Last potentially related work creation:
kasan_save_stack+0x1e/0x40
__kasan_record_aux_stack+0x97/0xb0
call_rcu+0x3d/0x3f0
erofs_shrink_workstation+0x11f/0x210
erofs_shrink_scan+0xdc/0x170
shrink_slab.constprop.0+0x296/0x530
drop_slab+0x1c/0x70
drop_caches_sysctl_handler+0x70/0x80
proc_sys_call_handler+0x20a/0x2f0
vfs_write+0x555/0x6c0
ksys_write+0xbe/0x160
do_syscall_64+0x3b/0x90
The root cause is that erofs_workgroup_unfreeze() doesn't reset to
orig_val thus it causes a race that the pcluster reuses unexpectedly
before freeing.
Since UP platforms are quite rare now, such path becomes unnecessary.
Let's drop such specific-designed path directly instead. |
| In the Linux kernel, the following vulnerability has been resolved:
scsi: core: Fix a use-after-free
There are two .exit_cmd_priv implementations. Both implementations use
resources associated with the SCSI host. Make sure that these resources are
still available when .exit_cmd_priv is called by waiting inside
scsi_remove_host() until the tag set has been freed.
This commit fixes the following use-after-free:
==================================================================
BUG: KASAN: use-after-free in srp_exit_cmd_priv+0x27/0xd0 [ib_srp]
Read of size 8 at addr ffff888100337000 by task multipathd/16727
Call Trace:
<TASK>
dump_stack_lvl+0x34/0x44
print_report.cold+0x5e/0x5db
kasan_report+0xab/0x120
srp_exit_cmd_priv+0x27/0xd0 [ib_srp]
scsi_mq_exit_request+0x4d/0x70
blk_mq_free_rqs+0x143/0x410
__blk_mq_free_map_and_rqs+0x6e/0x100
blk_mq_free_tag_set+0x2b/0x160
scsi_host_dev_release+0xf3/0x1a0
device_release+0x54/0xe0
kobject_put+0xa5/0x120
device_release+0x54/0xe0
kobject_put+0xa5/0x120
scsi_device_dev_release_usercontext+0x4c1/0x4e0
execute_in_process_context+0x23/0x90
device_release+0x54/0xe0
kobject_put+0xa5/0x120
scsi_disk_release+0x3f/0x50
device_release+0x54/0xe0
kobject_put+0xa5/0x120
disk_release+0x17f/0x1b0
device_release+0x54/0xe0
kobject_put+0xa5/0x120
dm_put_table_device+0xa3/0x160 [dm_mod]
dm_put_device+0xd0/0x140 [dm_mod]
free_priority_group+0xd8/0x110 [dm_multipath]
free_multipath+0x94/0xe0 [dm_multipath]
dm_table_destroy+0xa2/0x1e0 [dm_mod]
__dm_destroy+0x196/0x350 [dm_mod]
dev_remove+0x10c/0x160 [dm_mod]
ctl_ioctl+0x2c2/0x590 [dm_mod]
dm_ctl_ioctl+0x5/0x10 [dm_mod]
__x64_sys_ioctl+0xb4/0xf0
dm_ctl_ioctl+0x5/0x10 [dm_mod]
__x64_sys_ioctl+0xb4/0xf0
do_syscall_64+0x3b/0x90
entry_SYSCALL_64_after_hwframe+0x46/0xb0 |
| In the Linux kernel, the following vulnerability has been resolved:
can: peak_usb: fix use after free bugs
After calling peak_usb_netif_rx_ni(skb), dereferencing skb is unsafe.
Especially, the can_frame cf which aliases skb memory is accessed
after the peak_usb_netif_rx_ni().
Reordering the lines solves the issue. |
| In the Linux kernel, the following vulnerability has been resolved:
can: dev: can_restart: fix use after free bug
After calling netif_rx_ni(skb), dereferencing skb is unsafe.
Especially, the can_frame cf which aliases skb memory is accessed
after the netif_rx_ni() in:
stats->rx_bytes += cf->len;
Reordering the lines solves the issue. |
| In the Linux kernel, the following vulnerability has been resolved:
jffs2: fix use-after-free in jffs2_clear_xattr_subsystem
When we mount a jffs2 image, assume that the first few blocks of
the image are normal and contain at least one xattr-related inode,
but the next block is abnormal. As a result, an error is returned
in jffs2_scan_eraseblock(). jffs2_clear_xattr_subsystem() is then
called in jffs2_build_filesystem() and then again in
jffs2_do_fill_super().
Finally we can observe the following report:
==================================================================
BUG: KASAN: use-after-free in jffs2_clear_xattr_subsystem+0x95/0x6ac
Read of size 8 at addr ffff8881243384e0 by task mount/719
Call Trace:
dump_stack+0x115/0x16b
jffs2_clear_xattr_subsystem+0x95/0x6ac
jffs2_do_fill_super+0x84f/0xc30
jffs2_fill_super+0x2ea/0x4c0
mtd_get_sb+0x254/0x400
mtd_get_sb_by_nr+0x4f/0xd0
get_tree_mtd+0x498/0x840
jffs2_get_tree+0x25/0x30
vfs_get_tree+0x8d/0x2e0
path_mount+0x50f/0x1e50
do_mount+0x107/0x130
__se_sys_mount+0x1c5/0x2f0
__x64_sys_mount+0xc7/0x160
do_syscall_64+0x45/0x70
entry_SYSCALL_64_after_hwframe+0x44/0xa9
Allocated by task 719:
kasan_save_stack+0x23/0x60
__kasan_kmalloc.constprop.0+0x10b/0x120
kasan_slab_alloc+0x12/0x20
kmem_cache_alloc+0x1c0/0x870
jffs2_alloc_xattr_ref+0x2f/0xa0
jffs2_scan_medium.cold+0x3713/0x4794
jffs2_do_mount_fs.cold+0xa7/0x2253
jffs2_do_fill_super+0x383/0xc30
jffs2_fill_super+0x2ea/0x4c0
[...]
Freed by task 719:
kmem_cache_free+0xcc/0x7b0
jffs2_free_xattr_ref+0x78/0x98
jffs2_clear_xattr_subsystem+0xa1/0x6ac
jffs2_do_mount_fs.cold+0x5e6/0x2253
jffs2_do_fill_super+0x383/0xc30
jffs2_fill_super+0x2ea/0x4c0
[...]
The buggy address belongs to the object at ffff8881243384b8
which belongs to the cache jffs2_xattr_ref of size 48
The buggy address is located 40 bytes inside of
48-byte region [ffff8881243384b8, ffff8881243384e8)
[...]
==================================================================
The triggering of the BUG is shown in the following stack:
-----------------------------------------------------------
jffs2_fill_super
jffs2_do_fill_super
jffs2_do_mount_fs
jffs2_build_filesystem
jffs2_scan_medium
jffs2_scan_eraseblock <--- ERROR
jffs2_clear_xattr_subsystem <--- free
jffs2_clear_xattr_subsystem <--- free again
-----------------------------------------------------------
An error is returned in jffs2_do_mount_fs(). If the error is returned
by jffs2_sum_init(), the jffs2_clear_xattr_subsystem() does not need to
be executed. If the error is returned by jffs2_build_filesystem(), the
jffs2_clear_xattr_subsystem() also does not need to be executed again.
So move jffs2_clear_xattr_subsystem() from 'out_inohash' to 'out_root'
to fix this UAF problem. |
| In the Linux kernel, the following vulnerability has been resolved:
ubifs: rename_whiteout: Fix double free for whiteout_ui->data
'whiteout_ui->data' will be freed twice if space budget fail for
rename whiteout operation as following process:
rename_whiteout
dev = kmalloc
whiteout_ui->data = dev
kfree(whiteout_ui->data) // Free first time
iput(whiteout)
ubifs_free_inode
kfree(ui->data) // Double free!
KASAN reports:
==================================================================
BUG: KASAN: double-free or invalid-free in ubifs_free_inode+0x4f/0x70
Call Trace:
kfree+0x117/0x490
ubifs_free_inode+0x4f/0x70 [ubifs]
i_callback+0x30/0x60
rcu_do_batch+0x366/0xac0
__do_softirq+0x133/0x57f
Allocated by task 1506:
kmem_cache_alloc_trace+0x3c2/0x7a0
do_rename+0x9b7/0x1150 [ubifs]
ubifs_rename+0x106/0x1f0 [ubifs]
do_syscall_64+0x35/0x80
Freed by task 1506:
kfree+0x117/0x490
do_rename.cold+0x53/0x8a [ubifs]
ubifs_rename+0x106/0x1f0 [ubifs]
do_syscall_64+0x35/0x80
The buggy address belongs to the object at ffff88810238bed8 which
belongs to the cache kmalloc-8 of size 8
==================================================================
Let ubifs_free_inode() free 'whiteout_ui->data'. BTW, delete unused
assignment 'whiteout_ui->data_len = 0', process 'ubifs_evict_inode()
-> ubifs_jnl_delete_inode() -> ubifs_jnl_write_inode()' doesn't need it
(because 'inc_nlink(whiteout)' won't be excuted by 'goto out_release',
and the nlink of whiteout inode is 0). |
| In the Linux kernel, the following vulnerability has been resolved:
can: pch_can: pch_can_rx_normal: fix use after free
After calling netif_receive_skb(skb), dereferencing skb is unsafe.
Especially, the can_frame cf which aliases skb memory is dereferenced
just after the call netif_receive_skb(skb).
Reordering the lines solves the issue. |
| In the Linux kernel, the following vulnerability has been resolved:
net/sched: fq_pie: prevent dismantle issue
For some reason, fq_pie_destroy() did not copy
working code from pie_destroy() and other qdiscs,
thus causing elusive bug.
Before calling del_timer_sync(&q->adapt_timer),
we need to ensure timer will not rearm itself.
rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 0-....: (4416 ticks this GP) idle=60d/1/0x4000000000000000 softirq=10433/10434 fqs=2579
(t=10501 jiffies g=13085 q=3989)
NMI backtrace for cpu 0
CPU: 0 PID: 13 Comm: ksoftirqd/0 Not tainted 5.16.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
nmi_cpu_backtrace.cold+0x47/0x144 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x1b3/0x230 lib/nmi_backtrace.c:62
trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
rcu_dump_cpu_stacks+0x25e/0x3f0 kernel/rcu/tree_stall.h:343
print_cpu_stall kernel/rcu/tree_stall.h:627 [inline]
check_cpu_stall kernel/rcu/tree_stall.h:711 [inline]
rcu_pending kernel/rcu/tree.c:3878 [inline]
rcu_sched_clock_irq.cold+0x9d/0x746 kernel/rcu/tree.c:2597
update_process_times+0x16d/0x200 kernel/time/timer.c:1785
tick_sched_handle+0x9b/0x180 kernel/time/tick-sched.c:226
tick_sched_timer+0x1b0/0x2d0 kernel/time/tick-sched.c:1428
__run_hrtimer kernel/time/hrtimer.c:1685 [inline]
__hrtimer_run_queues+0x1c0/0xe50 kernel/time/hrtimer.c:1749
hrtimer_interrupt+0x31c/0x790 kernel/time/hrtimer.c:1811
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1086 [inline]
__sysvec_apic_timer_interrupt+0x146/0x530 arch/x86/kernel/apic/apic.c:1103
sysvec_apic_timer_interrupt+0x8e/0xc0 arch/x86/kernel/apic/apic.c:1097
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:638
RIP: 0010:write_comp_data kernel/kcov.c:221 [inline]
RIP: 0010:__sanitizer_cov_trace_const_cmp1+0x1d/0x80 kernel/kcov.c:273
Code: 54 c8 20 48 89 10 c3 66 0f 1f 44 00 00 53 41 89 fb 41 89 f1 bf 03 00 00 00 65 48 8b 0c 25 40 70 02 00 48 89 ce 4c 8b 54 24 08 <e8> 4e f7 ff ff 84 c0 74 51 48 8b 81 88 15 00 00 44 8b 81 84 15 00
RSP: 0018:ffffc90000d27b28 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff888064bf1bf0 RCX: ffff888011928000
RDX: ffff888011928000 RSI: ffff888011928000 RDI: 0000000000000003
RBP: ffff888064bf1c28 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff875d8295 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8880783dd300 R14: 0000000000000000 R15: 0000000000000000
pie_calculate_probability+0x405/0x7c0 net/sched/sch_pie.c:418
fq_pie_timer+0x170/0x2a0 net/sched/sch_fq_pie.c:383
call_timer_fn+0x1a5/0x6b0 kernel/time/timer.c:1421
expire_timers kernel/time/timer.c:1466 [inline]
__run_timers.part.0+0x675/0xa20 kernel/time/timer.c:1734
__run_timers kernel/time/timer.c:1715 [inline]
run_timer_softirq+0xb3/0x1d0 kernel/time/timer.c:1747
__do_softirq+0x29b/0x9c2 kernel/softirq.c:558
run_ksoftirqd kernel/softirq.c:921 [inline]
run_ksoftirqd+0x2d/0x60 kernel/softirq.c:913
smpboot_thread_fn+0x645/0x9c0 kernel/smpboot.c:164
kthread+0x405/0x4f0 kernel/kthread.c:327
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK> |
| In the Linux kernel, the following vulnerability has been resolved:
nfsd: fix use-after-free due to delegation race
A delegation break could arrive as soon as we've called vfs_setlease. A
delegation break runs a callback which immediately (in
nfsd4_cb_recall_prepare) adds the delegation to del_recall_lru. If we
then exit nfs4_set_delegation without hashing the delegation, it will be
freed as soon as the callback is done with it, without ever being
removed from del_recall_lru.
Symptoms show up later as use-after-free or list corruption warnings,
usually in the laundromat thread.
I suspect aba2072f4523 "nfsd: grant read delegations to clients holding
writes" made this bug easier to hit, but I looked as far back as v3.0
and it looks to me it already had the same problem. So I'm not sure
where the bug was introduced; it may have been there from the beginning. |
| In the Linux kernel, the following vulnerability has been resolved:
scsi: iscsi: Fix iscsi_task use after free
Commit d39df158518c ("scsi: iscsi: Have abort handler get ref to conn")
added iscsi_get_conn()/iscsi_put_conn() calls during abort handling but
then also changed the handling of the case where we detect an already
completed task where we now end up doing a goto to the common put/cleanup
code. This results in a iscsi_task use after free, because the common
cleanup code will do a put on the iscsi_task.
This reverts the goto and moves the iscsi_get_conn() to after we've checked
if the iscsi_task is valid. |
| In the Linux kernel, the following vulnerability has been resolved:
mac80211: fix use-after-free in CCMP/GCMP RX
When PN checking is done in mac80211, for fragmentation we need
to copy the PN to the RX struct so we can later use it to do a
comparison, since commit bf30ca922a0c ("mac80211: check defrag
PN against current frame").
Unfortunately, in that commit I used the 'hdr' variable without
it being necessarily valid, so use-after-free could occur if it
was necessary to reallocate (parts of) the frame.
Fix this by reloading the variable after the code that results
in the reallocations, if any.
This fixes https://bugzilla.kernel.org/show_bug.cgi?id=214401. |
| In the Linux kernel, the following vulnerability has been resolved:
scsi: iscsi: Fix conn use after free during resets
If we haven't done a unbind target call we can race where
iscsi_conn_teardown wakes up the EH thread and then frees the conn while
those threads are still accessing the conn ehwait.
We can only do one TMF per session so this just moves the TMF fields from
the conn to the session. We can then rely on the
iscsi_session_teardown->iscsi_remove_session->__iscsi_unbind_session call
to remove the target and it's devices, and know after that point there is
no device or scsi-ml callout trying to access the session. |
| 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:
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:
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:
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:
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--- |
