[syzbot] [iommu?] KASAN: slab-use-after-free Write in iommufd_eventq_fops_release

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 22f20375f5b7 Merge tag 'pci-v6.17-fixes-3' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16c29b12580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9ea369e307c9d48f
dashboard link: https://syzkaller.appspot.com/bug?extid=80620e2d0d0a33b09f93
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17795934580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17403642580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/76d1a12b1763/disk-22f20375.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8ebd247c9a40/vmlinux-22f20375.xz
kernel image: https://storage.googleapis.com/syzbot-assets/405482fe4099/bzImage-22f20375.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+80620e...@syzkaller.appspotmail.com

R13: 00007fb44b1d5fa0 R14: 00007fb44b1d5fa0 R15: 0000000000000003
</TASK>
==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: slab-use-after-free in atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:400 [inline]
BUG: KASAN: slab-use-after-free in __refcount_dec include/linux/refcount.h:455 [inline]
BUG: KASAN: slab-use-after-free in refcount_dec include/linux/refcount.h:476 [inline]
BUG: KASAN: slab-use-after-free in iommufd_eventq_fops_release+0x45/0xc0 drivers/iommu/iommufd/eventq.c:376
Write of size 4 at addr ffff888059c97804 by task syz.0.46/6164

CPU: 0 UID: 0 PID: 6164 Comm: syz.0.46 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xcd/0x630 mm/kasan/report.c:482
kasan_report+0xe0/0x110 mm/kasan/report.c:595
check_region_inline mm/kasan/generic.c:183 [inline]
kasan_check_range+0x100/0x1b0 mm/kasan/generic.c:189
instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
atomic_fetch_sub_release include/linux/atomic/atomic-instrumented.h:400 [inline]
__refcount_dec include/linux/refcount.h:455 [inline]
refcount_dec include/linux/refcount.h:476 [inline]
iommufd_eventq_fops_release+0x45/0xc0 drivers/iommu/iommufd/eventq.c:376
__fput+0x402/0xb70 fs/file_table.c:468
task_work_run+0x14d/0x240 kernel/task_work.c:227
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop+0xeb/0x110 kernel/entry/common.c:43
exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
do_syscall_64+0x41c/0x4c0 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb44af8eba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc3d692818 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: fffffffffffffff2 RBX: 00007fb44b1d5fa0 RCX: 00007fb44af8eba9
RDX: 0000000000000004 RSI: 0000000000003b8e RDI: 0000000000000006
RBP: 00007ffc3d692870 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fb44b1d5fa0 R14: 00007fb44b1d5fa0 R15: 0000000000000003
</TASK>

Allocated by task 6164:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:388 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:405
kasan_kmalloc include/linux/kasan.h:260 [inline]
__do_kmalloc_node mm/slub.c:4376 [inline]
__kmalloc_noprof+0x223/0x510 mm/slub.c:4388
kmalloc_noprof include/linux/slab.h:909 [inline]
kzalloc_noprof include/linux/slab.h:1039 [inline]
_iommufd_object_alloc+0x23/0x1a0 drivers/iommu/iommufd/main.c:40
_iommufd_object_alloc_ucmd+0xb2/0x160 drivers/iommu/iommufd/main.c:84
iommufd_fault_alloc+0x93/0x420 drivers/iommu/iommufd/eventq.c:430
iommufd_fops_ioctl+0x34d/0x540 drivers/iommu/iommufd/main.c:508
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:598 [inline]
__se_sys_ioctl fs/ioctl.c:584 [inline]
__x64_sys_ioctl+0x18b/0x210 fs/ioctl.c:584
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6164:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:576
poison_slab_object mm/kasan/common.c:243 [inline]
__kasan_slab_free+0x60/0x70 mm/kasan/common.c:275
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2422 [inline]
slab_free mm/slub.c:4695 [inline]
kfree+0x2b4/0x4d0 mm/slub.c:4894
iommufd_object_abort+0x10c/0x170 drivers/iommu/iommufd/main.c:124
iommufd_fops_ioctl+0x381/0x540 drivers/iommu/iommufd/main.c:512
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:598 [inline]
__se_sys_ioctl fs/ioctl.c:584 [inline]
__x64_sys_ioctl+0x18b/0x210 fs/ioctl.c:584
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888059c97800
which belongs to the cache kmalloc-cg-512 of size 512
The buggy address is located 4 bytes inside of
freed 512-byte region [ffff888059c97800, ffff888059c97a00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x59c94
head: order:2 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff888026413e01
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b84b140 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000100010 00000000f5000000 ffff888026413e01
head: 00fff00000000040 ffff88801b84b140 dead000000000122 0000000000000000
head: 0000000000000000 0000000000100010 00000000f5000000 ffff888026413e01
head: 00fff00000000002 ffffea0001672501 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000004
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5224, tgid 5224 (klogd), ts 132635729272, free_ts 132529818110
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1c0/0x230 mm/page_alloc.c:1851
prep_new_page mm/page_alloc.c:1859 [inline]
get_page_from_freelist+0x132b/0x38e0 mm/page_alloc.c:3858
__alloc_frozen_pages_noprof+0x261/0x23f0 mm/page_alloc.c:5148
alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2416
alloc_slab_page mm/slub.c:2492 [inline]
allocate_slab mm/slub.c:2660 [inline]
new_slab+0x247/0x330 mm/slub.c:2714
___slab_alloc+0xcf2/0x1750 mm/slub.c:3901
__slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3992
__slab_alloc_node mm/slub.c:4067 [inline]
slab_alloc_node mm/slub.c:4228 [inline]
__do_kmalloc_node mm/slub.c:4375 [inline]
__kmalloc_node_track_caller_noprof+0x2ee/0x510 mm/slub.c:4395
kmalloc_reserve+0xef/0x2c0 net/core/skbuff.c:600
__alloc_skb+0x166/0x380 net/core/skbuff.c:669
alloc_skb include/linux/skbuff.h:1336 [inline]
alloc_skb_with_frags+0xe0/0x860 net/core/skbuff.c:6665
sock_alloc_send_pskb+0x7fb/0x990 net/core/sock.c:2958
unix_dgram_sendmsg+0x3e9/0x17f0 net/unix/af_unix.c:2153
sock_sendmsg_nosec net/socket.c:714 [inline]
__sock_sendmsg net/socket.c:729 [inline]
__sys_sendto+0x4a3/0x520 net/socket.c:2228
__do_sys_sendto net/socket.c:2235 [inline]
__se_sys_sendto net/socket.c:2231 [inline]
__x64_sys_sendto+0xe0/0x1c0 net/socket.c:2231
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
page last free pid 5980 tgid 5980 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1395 [inline]
__free_frozen_pages+0x7d5/0x10f0 mm/page_alloc.c:2895
discard_slab mm/slub.c:2758 [inline]
__put_partials+0x165/0x1c0 mm/slub.c:3223
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x4d/0x120 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:340
kasan_slab_alloc include/linux/kasan.h:250 [inline]
slab_post_alloc_hook mm/slub.c:4191 [inline]
slab_alloc_node mm/slub.c:4240 [inline]
kmem_cache_alloc_noprof+0x1cb/0x3b0 mm/slub.c:4247
getname_flags.part.0+0x4c/0x550 fs/namei.c:146
getname_flags include/linux/audit.h:322 [inline]
getname include/linux/fs.h:2919 [inline]
__do_sys_unlink fs/namei.c:4696 [inline]
__se_sys_unlink fs/namei.c:4694 [inline]
__x64_sys_unlink+0xb0/0x110 fs/namei.c:4694
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
ffff888059c97700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888059c97780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888059c97800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff888059c97880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888059c97900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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