[moderation] [sound?] KASAN: slab-use-after-free Read in snd_pcm_oss_look_for_setup (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6916d5703ddf Merge tag 'drm-fixes-2026-05-16' of https://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15012536580000
kernel config: https://syzkaller.appspot.com/x/.config?x=d0f0911eedbc130a
dashboard link: https://syzkaller.appspot.com/bug?extid=b664d7b275e04ef805e3
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
CC: [linux-...@vger.kernel.org linux...@vger.kernel.org pe...@perex.cz ti...@suse.com]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1efefe7c73e1/disk-6916d570.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1dcf16f12a0f/vmlinux-6916d570.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7bc2e1f3e5cd/bzImage-6916d570.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b664d7...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in snd_pcm_oss_look_for_setup+0x2d3/0x370 sound/core/oss/pcm_oss.c:2355
Read of size 8 at addr ffff888022f56d00 by task syz.1.988/10837

CPU: 0 UID: 0 PID: 10837 Comm: syz.1.988 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0x13d/0x4b0 mm/kasan/report.c:482
kasan_report+0xdf/0x1d0 mm/kasan/report.c:595
snd_pcm_oss_look_for_setup+0x2d3/0x370 sound/core/oss/pcm_oss.c:2355
snd_pcm_oss_open+0xddc/0x1390 sound/core/oss/pcm_oss.c:2521
soundcore_open+0x2e3/0x5a0 sound/sound_core.c:594
chrdev_open+0x234/0x6a0 fs/char_dev.c:411
do_dentry_open+0x6d8/0x1660 fs/open.c:947
vfs_open+0x82/0x3f0 fs/open.c:1079
do_open fs/namei.c:4699 [inline]
path_openat+0x208c/0x31a0 fs/namei.c:4858
do_file_open+0x20e/0x430 fs/namei.c:4887
do_sys_openat2+0x10d/0x1e0 fs/open.c:1364
do_sys_open fs/open.c:1370 [inline]
__do_sys_openat fs/open.c:1386 [inline]
__se_sys_openat fs/open.c:1381 [inline]
__x64_sys_openat+0x12d/0x210 fs/open.c:1381
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fda1919ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fda1a0fa028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fda19416090 RCX: 00007fda1919ce59
RDX: 0000000000020342 RSI: 00002000000001c0 RDI: ffffffffffffff9c
RBP: 00007fda19232d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fda19416128 R14: 00007fda19416090 R15: 00007ffdc6f4a5c8
</TASK>

Allocated by task 10831:
kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
kasan_save_track+0x14/0x30 mm/kasan/common.c:78
poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
kmalloc_noprof include/linux/slab.h:950 [inline]
snd_pcm_oss_proc_write+0x736/0x9a0 sound/core/oss/pcm_oss.c:3058
snd_info_text_entry_release+0xfb/0x260 sound/core/info.c:386
close_pdeo.part.0+0xdf/0x2e0 fs/proc/inode.c:242
close_pdeo fs/proc/inode.c:540 [inline]
proc_reg_release+0x2df/0x350 fs/proc/inode.c:546
__fput+0x3ff/0xb50 fs/file_table.c:510
task_work_run+0x150/0x240 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
exit_to_user_mode_loop+0x107/0x4f0 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
do_syscall_64+0x6f2/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 10831:
kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
kasan_save_track+0x14/0x30 mm/kasan/common.c:78
kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
poison_slab_object mm/kasan/common.c:253 [inline]
__kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
kasan_slab_free include/linux/kasan.h:235 [inline]
slab_free_hook mm/slub.c:2689 [inline]
slab_free mm/slub.c:6250 [inline]
kfree+0x223/0x6c0 mm/slub.c:6565
snd_pcm_oss_proc_write+0x7b1/0x9a0 sound/core/oss/pcm_oss.c:3072
snd_info_text_entry_release+0xfb/0x260 sound/core/info.c:386
close_pdeo.part.0+0xdf/0x2e0 fs/proc/inode.c:242
close_pdeo fs/proc/inode.c:540 [inline]
proc_reg_release+0x2df/0x350 fs/proc/inode.c:546
__fput+0x3ff/0xb50 fs/file_table.c:510
task_work_run+0x150/0x240 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:67 [inline]
exit_to_user_mode_loop+0x107/0x4f0 kernel/entry/common.c:98
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
do_syscall_64+0x6f2/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff888022f56d00
which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes inside of
freed 32-byte region [ffff888022f56d00, ffff888022f56d20)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888022f56240 pfn:0x22f56
flags: 0xfff00000000200(workingset|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000200 ffff88813fe2f780 ffffea0000d47510 ffffea0000ca7a10
raw: ffff888022f56240 000000080040003f 00000000f5000000 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 0xd2800(GFP_NOWAIT|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5387, tgid 5387 (getty), ts 194081637728, free_ts 194058318447
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x153/0x170 mm/page_alloc.c:1858
prep_new_page mm/page_alloc.c:1866 [inline]
get_page_from_freelist+0x11a6/0x33b0 mm/page_alloc.c:3946
__alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5226
alloc_slab_page mm/slub.c:3278 [inline]
allocate_slab mm/slub.c:3467 [inline]
new_slab+0xa6/0x6c0 mm/slub.c:3525
refill_objects+0x277/0x420 mm/slub.c:7271
refill_sheaf mm/slub.c:2816 [inline]
__pcs_replace_empty_main+0x375/0x650 mm/slub.c:4651
alloc_from_pcs mm/slub.c:4749 [inline]
slab_alloc_node mm/slub.c:4883 [inline]
__kmalloc_cache_noprof+0x493/0x6f0 mm/slub.c:5414
kmalloc_noprof include/linux/slab.h:950 [inline]
slab_free_hook mm/slub.c:2641 [inline]
slab_free mm/slub.c:6250 [inline]
kmem_cache_free+0x41e/0x6c0 mm/slub.c:6377
tear_down_vmas+0x2a5/0x600 mm/mmap.c:1262
exit_mmap+0x469/0xa10 mm/mmap.c:1320
__mmput+0x12a/0x410 kernel/fork.c:1178
mmput+0x67/0x80 kernel/fork.c:1201
exit_mm kernel/exit.c:582 [inline]
do_exit+0x8b2/0x2af0 kernel/exit.c:964
do_group_exit+0xd5/0x2a0 kernel/exit.c:1119
__do_sys_exit_group kernel/exit.c:1130 [inline]
__se_sys_exit_group kernel/exit.c:1128 [inline]
__x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1128
x64_sys_call+0x102c/0x1530 arch/x86/include/generated/asm/syscalls_64.h:232
page last free pid 15 tgid 15 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1402 [inline]
__free_frozen_pages+0x747/0x1040 mm/page_alloc.c:2943
__pagetable_free include/linux/mm.h:3661 [inline]
pagetable_free include/linux/mm.h:3685 [inline]
pagetable_dtor_free include/linux/mm.h:3784 [inline]
__tlb_remove_table include/asm-generic/tlb.h:221 [inline]
__tlb_remove_table_free mm/mmu_gather.c:228 [inline]
tlb_remove_table_rcu+0x2cf/0x380 mm/mmu_gather.c:291
rcu_do_batch kernel/rcu/tree.c:2617 [inline]
rcu_core+0x5a2/0x10d0 kernel/rcu/tree.c:2869
handle_softirqs+0x1ea/0xa00 kernel/softirq.c:622
run_ksoftirqd kernel/softirq.c:1076 [inline]
run_ksoftirqd+0x38/0x60 kernel/softirq.c:1068
smpboot_thread_fn+0x3d3/0xaa0 kernel/smpboot.c:160
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
ffff888022f56c00: fa fb fb fb fc fc fc fc 00 00 00 00 fc fc fc fc
ffff888022f56c80: 00 00 00 fc fc fc fc fc fa fb fb fb fc fc fc fc
>ffff888022f56d00: fa fb fb fb fc fc fc fc 00 00 00 00 fc fc fc fc
^
ffff888022f56d80: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
ffff888022f56e00: 00 00 00 fc fc fc fc fc fa fb fb fb fc fc fc fc
==================================================================


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