[syzbot] [bpf?] KASAN: slab-use-after-free Read in bpf_link_free

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 727900b675b7 Add linux-next specific files for 20240403
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17bf53c5180000
kernel config: https://syzkaller.appspot.com/x/.config?x=afcaf46d374cec8c
dashboard link: https://syzkaller.appspot.com/bug?extid=b3851d693eb8edda5c7d
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f8fb4daa7a83/disk-727900b6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d2a6994aee53/vmlinux-727900b6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6759e5411c39/bzImage-727900b6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b3851d...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in bpf_link_free+0x234/0x2d0 kernel/bpf/syscall.c:3065
Read of size 8 at addr ffff88802e688c10 by task syz-executor.3/5206

CPU: 0 PID: 5206 Comm: syz-executor.3 Not tainted 6.9.0-rc2-next-20240403-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x169/0x550 mm/kasan/report.c:488
kasan_report+0x143/0x180 mm/kasan/report.c:601
bpf_link_free+0x234/0x2d0 kernel/bpf/syscall.c:3065
bpf_link_put_direct kernel/bpf/syscall.c:3093 [inline]
bpf_link_release+0x7b/0x90 kernel/bpf/syscall.c:3100
__fput+0x429/0x8a0 fs/file_table.c:422
task_work_run+0x24f/0x310 kernel/task_work.c:180
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0xa1b/0x27e0 kernel/exit.c:878
do_group_exit+0x207/0x2c0 kernel/exit.c:1027
get_signal+0x16a1/0x1740 kernel/signal.c:2911
arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0xc9/0x360 kernel/entry/common.c:218
do_syscall_64+0x10a/0x240 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x72/0x7a
RIP: 0033:0x7f803547dde9
Code: Unable to access opcode bytes at 0x7f803547ddbf.
RSP: 002b:00007f80361c80c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: 0000000000000006 RBX: 00007f80355abf80 RCX: 00007f803547dde9
RDX: 0000000000000010 RSI: 0000000020000040 RDI: 0000000000000011
RBP: 00007f80354ca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f80355abf80 R15: 00007fff8c6d4fc8
</TASK>

Allocated by task 5206:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:370 [inline]
__kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:387
kasan_kmalloc include/linux/kasan.h:211 [inline]
kmalloc_trace_noprof+0x19c/0x2b0 mm/slub.c:4100
kmalloc_noprof include/linux/slab.h:660 [inline]
kzalloc_noprof include/linux/slab.h:775 [inline]
bpf_raw_tp_link_attach+0x2a0/0x6e0 kernel/bpf/syscall.c:3845
bpf_raw_tracepoint_open+0x1c2/0x240 kernel/bpf/syscall.c:3892
__sys_bpf+0x3c0/0x810 kernel/bpf/syscall.c:5702
__do_sys_bpf kernel/bpf/syscall.c:5767 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5765 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5765
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x72/0x7a

Freed by task 24:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
poison_slab_object+0xe0/0x150 mm/kasan/common.c:240
__kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
kasan_slab_free include/linux/kasan.h:184 [inline]
slab_free_hook mm/slub.c:2180 [inline]
slab_free mm/slub.c:4384 [inline]
kfree+0x149/0x350 mm/slub.c:4505
rcu_do_batch kernel/rcu/tree.c:2559 [inline]
rcu_core+0xafd/0x1830 kernel/rcu/tree.c:2833
__do_softirq+0x2c6/0x980 kernel/softirq.c:554

Last potentially related work creation:
kasan_save_stack+0x3f/0x60 mm/kasan/common.c:47
__kasan_record_aux_stack+0xac/0xc0 mm/kasan/generic.c:541
__call_rcu_common kernel/rcu/tree.c:3096 [inline]
call_rcu+0x167/0xa70 kernel/rcu/tree.c:3200
bpf_link_free+0x1f8/0x2d0 kernel/bpf/syscall.c:3063
bpf_link_put_direct kernel/bpf/syscall.c:3093 [inline]
bpf_link_release+0x7b/0x90 kernel/bpf/syscall.c:3100
__fput+0x429/0x8a0 fs/file_table.c:422
task_work_run+0x24f/0x310 kernel/task_work.c:180
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0xa1b/0x27e0 kernel/exit.c:878
do_group_exit+0x207/0x2c0 kernel/exit.c:1027
get_signal+0x16a1/0x1740 kernel/signal.c:2911
arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0xc9/0x360 kernel/entry/common.c:218
do_syscall_64+0x10a/0x240 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x72/0x7a

The buggy address belongs to the object at ffff88802e688c00
which belongs to the cache kmalloc-128 of size 128
The buggy address is located 16 bytes inside of
freed 128-byte region [ffff88802e688c00, ffff88802e688c80)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2e688
flags: 0xfff80000000000(node=0|zone=1|lastcpupid=0xfff)
page_type: 0xffffefff(slab)
raw: 00fff80000000000 ffff8880150418c0 ffffea0000b40100 dead000000000002
raw: 0000000000000000 0000000000100010 00000001ffffefff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 4551, tgid 587604050 (udevadm), ts 4551, free_ts 25547020786
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1490
prep_new_page mm/page_alloc.c:1498 [inline]
get_page_from_freelist+0x2e7e/0x2f40 mm/page_alloc.c:3454
__alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4712
__alloc_pages_node_noprof include/linux/gfp.h:244 [inline]
alloc_pages_node_noprof include/linux/gfp.h:271 [inline]
alloc_slab_page+0x5f/0x120 mm/slub.c:2249
allocate_slab+0x5a/0x2e0 mm/slub.c:2412
new_slab mm/slub.c:2465 [inline]
___slab_alloc+0xcd1/0x14b0 mm/slub.c:3615
__slab_alloc+0x58/0xa0 mm/slub.c:3705
__slab_alloc_node mm/slub.c:3758 [inline]
slab_alloc_node mm/slub.c:3936 [inline]
kmalloc_trace_noprof+0x1d5/0x2b0 mm/slub.c:4095
kmalloc_noprof include/linux/slab.h:660 [inline]
kzalloc_noprof include/linux/slab.h:775 [inline]
kernfs_get_open_node fs/kernfs/file.c:525 [inline]
kernfs_fop_open+0x800/0xcd0 fs/kernfs/file.c:693
do_dentry_open+0x907/0x15a0 fs/open.c:955
do_open fs/namei.c:3642 [inline]
path_openat+0x2860/0x3240 fs/namei.c:3799
do_filp_open+0x235/0x490 fs/namei.c:3826
do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
do_sys_open fs/open.c:1421 [inline]
__do_sys_openat fs/open.c:1437 [inline]
__se_sys_openat fs/open.c:1432 [inline]
__x64_sys_openat+0x247/0x2a0 fs/open.c:1432
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x72/0x7a
page last free pid 4544 tgid 4544 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1110 [inline]
free_unref_page+0xd3c/0xec0 mm/page_alloc.c:2617
discard_slab mm/slub.c:2511 [inline]
__put_partials+0xeb/0x130 mm/slub.c:2980
put_cpu_partial+0x17c/0x250 mm/slub.c:3055
__slab_free+0x2ea/0x3d0 mm/slub.c:4254
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x9e/0x140 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x14f/0x170 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x23/0x80 mm/kasan/common.c:322
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook mm/slub.c:3888 [inline]
slab_alloc_node mm/slub.c:3948 [inline]
kmem_cache_alloc_node_noprof+0x16b/0x310 mm/slub.c:3991
kmalloc_reserve+0xa8/0x2a0 net/core/skbuff.c:577
__alloc_skb+0x1f3/0x440 net/core/skbuff.c:668
netlink_sendmsg+0x637/0xcb0 net/netlink/af_netlink.c:1880
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg+0x221/0x270 net/socket.c:745
____sys_sendmsg+0x525/0x7d0 net/socket.c:2584
___sys_sendmsg net/socket.c:2638 [inline]
__sys_sendmsg+0x2b0/0x3a0 net/socket.c:2667
do_syscall_64+0xfb/0x240
entry_SYSCALL_64_after_hwframe+0x72/0x7a

Memory state around the buggy address:
ffff88802e688b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc
ffff88802e688b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88802e688c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88802e688c80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802e688d00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


---
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[Andrii Nakryiko]

On Thu, Apr 4, 2024 at 2:19 PM syzbot
<syzbot+b3851d...@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 727900b675b7 Add linux-next specific files for 20240403
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=17bf53c5180000
> kernel config: https://syzkaller.appspot.com/x/.config?x=afcaf46d374cec8c
> dashboard link: https://syzkaller.appspot.com/bug?extid=b3851d693eb8edda5c7d
> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/f8fb4daa7a83/disk-727900b6.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/d2a6994aee53/vmlinux-727900b6.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/6759e5411c39/bzImage-727900b6.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b3851d...@syzkaller.appspotmail.com
>
> ==================================================================
> BUG: KASAN: slab-use-after-free in bpf_link_free+0x234/0x2d0 kernel/bpf/syscall.c:3065
> Read of size 8 at addr ffff88802e688c10 by task syz-executor.3/5206
>

syz fix: bpf: support deferring bpf_link dealloc to after RCU grace period

[Aleksandr Nogikh]

#syz fix: bpf: support deferring bpf_link dealloc to after RCU grace period

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 9ed46da14b9b Add linux-next specific files for 20240412
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=126eafeb180000
kernel config: https://syzkaller.appspot.com/x/.config?x=7ea0abc478c49859

dashboard link: https://syzkaller.appspot.com/bug?extid=b3851d693eb8edda5c7d
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=131da293180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/fc649744d68c/disk-9ed46da1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/11eab7b9945d/vmlinux-9ed46da1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e7885afd198d/bzImage-9ed46da1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b3851d...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in bpf_link_free+0x234/0x2d0 kernel/bpf/syscall.c:3065

Read of size 8 at addr ffff88802c1ba010 by task syz-executor.1/10495

CPU: 0 PID: 10495 Comm: syz-executor.1 Not tainted 6.9.0-rc3-next-20240412-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x169/0x550 mm/kasan/report.c:488
kasan_report+0x143/0x180 mm/kasan/report.c:601
bpf_link_free+0x234/0x2d0 kernel/bpf/syscall.c:3065
bpf_link_put_direct kernel/bpf/syscall.c:3093 [inline]
bpf_link_release+0x7b/0x90 kernel/bpf/syscall.c:3100

__fput+0x406/0x8b0 fs/file_table.c:422
__do_sys_close fs/open.c:1556 [inline]
__se_sys_close fs/open.c:1541 [inline]
__x64_sys_close+0x7f/0x110 fs/open.c:1541
do_syscall_x64 arch/x86/entry/common.c:74 [inline]
do_syscall_64+0xfa/0x250 arch/x86/entry/common.c:105
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f53a7e7cd5a
Code: 48 3d 00 f0 ff ff 77 48 c3 0f 1f 80 00 00 00 00 48 83 ec 18 89 7c 24 0c e8 03 7f 02 00 8b 7c 24 0c 89 c2 b8 03 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 36 89 d7 89 44 24 0c e8 63 7f 02 00 8b 44 24
RSP: 002b:00007ffcb2194010 EFLAGS: 00000293 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 000000000000000f RCX: 00007f53a7e7cd5a
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000000000e
RBP: 0000000000000032 R08: 0000001b33560000 R09: 00007f53a7fac05c
R10: 00007ffcb2194160 R11: 0000000000000293 R12: 00007f53a7a029d8
R13: ffffffffffffffff R14: 00007f53a7a00000 R15: 000000000003fe92
</TASK>

Allocated by task 10497:

kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:370 [inline]
__kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:387
kasan_kmalloc include/linux/kasan.h:211 [inline]

kmalloc_trace_noprof+0x19c/0x2b0 mm/slub.c:4109

kmalloc_noprof include/linux/slab.h:660 [inline]
kzalloc_noprof include/linux/slab.h:775 [inline]
bpf_raw_tp_link_attach+0x2a0/0x6e0 kernel/bpf/syscall.c:3845
bpf_raw_tracepoint_open+0x1c2/0x240 kernel/bpf/syscall.c:3892

__sys_bpf+0x3c0/0x810 kernel/bpf/syscall.c:5706
__do_sys_bpf kernel/bpf/syscall.c:5771 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5769 [inline]
__x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:5769
do_syscall_x64 arch/x86/entry/common.c:74 [inline]
do_syscall_64+0xfa/0x250 arch/x86/entry/common.c:105
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 16:

kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
poison_slab_object+0xe0/0x150 mm/kasan/common.c:240
__kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
kasan_slab_free include/linux/kasan.h:184 [inline]

slab_free_hook mm/slub.c:2190 [inline]
slab_free mm/slub.c:4393 [inline]
kfree+0x149/0x350 mm/slub.c:4514
rcu_do_batch kernel/rcu/tree.c:2565 [inline]
rcu_core+0xafd/0x1830 kernel/rcu/tree.c:2839

__do_softirq+0x2c6/0x980 kernel/softirq.c:554

Last potentially related work creation:
kasan_save_stack+0x3f/0x60 mm/kasan/common.c:47
__kasan_record_aux_stack+0xac/0xc0 mm/kasan/generic.c:541

__call_rcu_common kernel/rcu/tree.c:3102 [inline]
call_rcu+0x167/0xa70 kernel/rcu/tree.c:3206

bpf_link_free+0x1f8/0x2d0 kernel/bpf/syscall.c:3063
bpf_link_put_direct kernel/bpf/syscall.c:3093 [inline]
bpf_link_release+0x7b/0x90 kernel/bpf/syscall.c:3100

__fput+0x406/0x8b0 fs/file_table.c:422
__do_sys_close fs/open.c:1556 [inline]
__se_sys_close fs/open.c:1541 [inline]
__x64_sys_close+0x7f/0x110 fs/open.c:1541
do_syscall_x64 arch/x86/entry/common.c:74 [inline]
do_syscall_64+0xfa/0x250 arch/x86/entry/common.c:105
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88802c1ba000

which belongs to the cache kmalloc-128 of size 128
The buggy address is located 16 bytes inside of

freed 128-byte region [ffff88802c1ba000, ffff88802c1ba080)

The buggy address belongs to the physical page:

page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2c1ba

flags: 0xfff80000000000(node=0|zone=1|lastcpupid=0xfff)
page_type: 0xffffefff(slab)

raw: 00fff80000000000 ffff8880150418c0 dead000000000100 dead000000000122
raw: 0000000000000000 0000000080100010 00000001ffffefff 0000000000000000

page dumped because: kasan: bad access detected
page_owner tracks the page as allocated

page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 5104, tgid 1807949953 (udevd), ts 5104, free_ts 194993482569
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1474
prep_new_page mm/page_alloc.c:1482 [inline]
get_page_from_freelist+0x2ce2/0x2d90 mm/page_alloc.c:3444
__alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4702

__alloc_pages_node_noprof include/linux/gfp.h:244 [inline]
alloc_pages_node_noprof include/linux/gfp.h:271 [inline]

alloc_slab_page+0x5f/0x120 mm/slub.c:2259
allocate_slab+0x5a/0x2e0 mm/slub.c:2422
new_slab mm/slub.c:2475 [inline]
___slab_alloc+0xcd1/0x14b0 mm/slub.c:3624
__slab_alloc+0x58/0xa0 mm/slub.c:3714
__slab_alloc_node mm/slub.c:3767 [inline]
slab_alloc_node mm/slub.c:3945 [inline]
kmalloc_trace_noprof+0x1d5/0x2b0 mm/slub.c:4104

kmalloc_noprof include/linux/slab.h:660 [inline]
kzalloc_noprof include/linux/slab.h:775 [inline]
kernfs_get_open_node fs/kernfs/file.c:525 [inline]
kernfs_fop_open+0x800/0xcd0 fs/kernfs/file.c:693

do_dentry_open+0x907/0x15f0 fs/open.c:955
do_open fs/namei.c:3642 [inline]
path_openat+0x289f/0x3280 fs/namei.c:3799

do_filp_open+0x235/0x490 fs/namei.c:3826
do_sys_openat2+0x13e/0x1d0 fs/open.c:1406
do_sys_open fs/open.c:1421 [inline]
__do_sys_openat fs/open.c:1437 [inline]
__se_sys_openat fs/open.c:1432 [inline]
__x64_sys_openat+0x247/0x2a0 fs/open.c:1432

do_syscall_x64 arch/x86/entry/common.c:74 [inline]
do_syscall_64+0xfa/0x250 arch/x86/entry/common.c:105
entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5198 tgid 5198 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1094 [inline]
free_unref_page+0xd22/0xea0 mm/page_alloc.c:2607
vfree+0x186/0x2e0 mm/vmalloc.c:3338
delayed_vfree_work+0x56/0x80 mm/vmalloc.c:3259
process_one_work kernel/workqueue.c:3218 [inline]
process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3299
worker_thread+0x86d/0xd70 kernel/workqueue.c:3380
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Memory state around the buggy address:

ffff88802c1b9f00: fa fb fb fb fb fb fb fb fb fb fb fc fc fc fc fa
ffff88802c1b9f80: fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc
>ffff88802c1ba000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88802c1ba080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802c1ba100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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