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KASAN: slab-use-after-free Read in snd_pcm_action_single (2)

Status: moderation: reported on 2026/04/22 10:49
Subsystems: sound
[Documentation on labels]
Reported-by: syzbot+8fa95c41eafbc9d2ff6f@syzkaller.appspotmail.com
First crash: 6d07h, last: 6d07h
✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision Error
501a594d-fcc2-4db6-b77e-6223567d6758 moderation Actionable: ✅  Confident: ✅  KASAN: slab-use-after-free Read in snd_pcm_action_single (2) 2026/04/22 11:50 2026/04/22 11:50 2026/04/22 12:18 0b6ab7eca89bfc27b5fb0aaa26b248298864892e
Discussions (2)
Title Replies (including bot) Last reply
[PATCH v2] ALSA: aloop: Fix peer runtime UAF during format-change stop 1 (1) 2026/04/24 12:48
[PATCH] ALSA: aloop: Fix peer runtime UAF during format-change stop 3 (3) 2026/04/24 12:14
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in snd_pcm_action_single sound 19 4 312d 469d 0/29 auto-obsoleted due to no activity on 2025/09/24 17:17

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
BUG: KASAN: slab-use-after-free in _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:166
Read of size 1 at addr ffff88801353a180 by task syz.5.350/7618

CPU: 0 UID: 0 PID: 7618 Comm: syz.5.350 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
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
 __kasan_check_byte+0x36/0x50 mm/kasan/common.c:574
 kasan_check_byte include/linux/kasan.h:402 [inline]
 lock_acquire kernel/locking/lockdep.c:5842 [inline]
 lock_acquire+0x12a/0x370 kernel/locking/lockdep.c:5825
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
 _raw_spin_lock_irqsave+0x3a/0x60 kernel/locking/spinlock.c:166
 __wake_up_common_lock kernel/sched/wait.c:124 [inline]
 __wake_up+0x1c/0x60 kernel/sched/wait.c:146
 snd_pcm_action_single+0x10d/0x150 sound/core/pcm_native.c:1336
 snd_pcm_action+0x70/0x90 sound/core/pcm_native.c:1417
 loopback_check_format sound/drivers/aloop.c:400 [inline]
 loopback_trigger+0x805/0x1fb0 sound/drivers/aloop.c:421
 snd_pcm_do_start sound/core/pcm_native.c:1478 [inline]
 snd_pcm_do_start+0xd4/0x1f0 sound/core/pcm_native.c:1471
 snd_pcm_action_single+0x80/0x150 sound/core/pcm_native.c:1334
 snd_pcm_action+0x70/0x90 sound/core/pcm_native.c:1417
 __snd_pcm_lib_xfer+0x177b/0x20a0 sound/core/pcm_lib.c:2405
 snd_pcm_oss_write3+0x8f/0x180 sound/core/oss/pcm_oss.c:1247
 snd_pcm_oss_write2+0x32b/0x400 sound/core/oss/pcm_oss.c:1391
 snd_pcm_oss_sync1+0x1da/0x4d0 sound/core/oss/pcm_oss.c:1625
 snd_pcm_oss_sync+0x66a/0x840 sound/core/oss/pcm_oss.c:1701
 snd_pcm_oss_release+0x238/0x300 sound/core/oss/pcm_oss.c:2584
 __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+0x100/0x4a0 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:328 [inline]
 __do_fast_syscall_32+0x608/0x950 arch/x86/entry/syscall_32.c:310
 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf703efcc
Code: d2 74 05 c1 e8 0c 89 02 8b 5d fc 31 c0 c9 c3 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 0f 1f 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 2e 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00 58 b8
RSP: 002b:00000000fff9febc EFLAGS: 00000202 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 000000000000001e
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>

Allocated by task 7619:
 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]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 snd_pcm_attach_substream+0x436/0xd20 sound/core/pcm.c:938
 snd_pcm_open_substream+0x90/0x1850 sound/core/pcm_native.c:2797
 snd_pcm_oss_open_file sound/core/oss/pcm_oss.c:2448 [inline]
 snd_pcm_oss_open+0x735/0x1390 sound/core/oss/pcm_oss.c:2529
 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_compat_sys_openat fs/open.c:1432 [inline]
 __se_compat_sys_openat fs/open.c:1430 [inline]
 __ia32_compat_sys_openat+0x12d/0x210 fs/open.c:1430
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
 __do_fast_syscall_32+0xe7/0x950 arch/x86/entry/syscall_32.c:307
 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Freed by task 7619:
 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:6246 [inline]
 kfree+0x223/0x6c0 mm/slub.c:6561
 snd_pcm_detach_substream+0x1d7/0x390 sound/core/pcm.c:1003
 snd_pcm_release_substream+0x5b/0x70 sound/core/pcm_native.c:2770
 snd_pcm_oss_release_file sound/core/oss/pcm_oss.c:2407 [inline]
 snd_pcm_oss_release_file sound/core/oss/pcm_oss.c:2399 [inline]
 snd_pcm_oss_release+0x16f/0x300 sound/core/oss/pcm_oss.c:2586
 __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+0x100/0x4a0 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:328 [inline]
 __do_fast_syscall_32+0x608/0x950 arch/x86/entry/syscall_32.c:310
 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e

The buggy address belongs to the object at ffff88801353a000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 384 bytes inside of
 freed 2048-byte region [ffff88801353a000, ffff88801353a800)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x13538
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801b842f00 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800080008 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801b842f00 dead000000000100 dead000000000122
head: 0000000000000000 0000000800080008 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5958, tgid 5958 (syz-executor), ts 102791007525, free_ts 30116838353
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x153/0x170 mm/page_alloc.c:1860
 prep_new_page mm/page_alloc.c:1868 [inline]
 get_page_from_freelist+0x11a6/0x33b0 mm/page_alloc.c:3948
 __alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5228
 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:7251
 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]
 __do_kmalloc_node mm/slub.c:5294 [inline]
 __kmalloc_node_track_caller_noprof+0x694/0x850 mm/slub.c:5403
 kmalloc_reserve+0xe8/0x350 net/core/skbuff.c:635
 __alloc_skb+0x185/0x710 net/core/skbuff.c:713
 alloc_skb include/linux/skbuff.h:1383 [inline]
 nlmsg_new include/net/netlink.h:1055 [inline]
 inet6_ifinfo_notify+0x77/0x140 net/ipv6/addrconf.c:6191
 addrconf_notify+0xb54/0x1ba0 net/ipv6/addrconf.c:3772
 notifier_call_chain+0x99/0x400 kernel/notifier.c:85
 call_netdevice_notifiers_info+0xbe/0x110 net/core/dev.c:2249
 call_netdevice_notifiers_extack net/core/dev.c:2287 [inline]
 call_netdevice_notifiers net/core/dev.c:2301 [inline]
 __dev_notify_flags+0x12c/0x2e0 net/core/dev.c:9849
 netif_change_flags+0x108/0x160 net/core/dev.c:9878
 do_setlink.isra.0+0x1abb/0x3e50 net/core/rtnetlink.c:3180
page last free pid 5355 tgid 5355 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1404 [inline]
 __free_frozen_pages+0x747/0x1040 mm/page_alloc.c:2945
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x47/0xf0 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x1a0/0x1f0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4569 [inline]
 slab_alloc_node mm/slub.c:4898 [inline]
 kmem_cache_alloc_noprof+0x241/0x6e0 mm/slub.c:4905
 alloc_filename fs/namei.c:142 [inline]
 do_getname+0x35/0x390 fs/namei.c:182
 getname include/linux/fs.h:2533 [inline]
 class_filename_constructor include/linux/fs.h:2560 [inline]
 do_sys_openat2+0xc5/0x1e0 fs/open.c:1363
 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

Memory state around the buggy address:
 ffff88801353a080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801353a100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88801353a180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                   ^
 ffff88801353a200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88801353a280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
----------------
Code disassembly (best guess):
   0:	d2 74 05 c1          	shlb   %cl,-0x3f(%rbp,%rax,1)
   4:	e8 0c 89 02 8b       	call   0x8b028915
   9:	5d                   	pop    %rbp
   a:	fc                   	cld
   b:	31 c0                	xor    %eax,%eax
   d:	c9                   	leave
   e:	c3                   	ret
   f:	90                   	nop
  10:	90                   	nop
  11:	90                   	nop
  12:	90                   	nop
  13:	90                   	nop
  14:	90                   	nop
  15:	90                   	nop
  16:	90                   	nop
  17:	90                   	nop
  18:	90                   	nop
  19:	90                   	nop
  1a:	90                   	nop
  1b:	90                   	nop
  1c:	90                   	nop
  1d:	90                   	nop
  1e:	0f 1f 00             	nopl   (%rax)
  21:	51                   	push   %rcx
  22:	52                   	push   %rdx
  23:	55                   	push   %rbp
  24:	89 e5                	mov    %esp,%ebp
  26:	0f 34                	sysenter
  28:	cd 80                	int    $0x80
* 2a:	5d                   	pop    %rbp <-- trapping instruction
  2b:	5a                   	pop    %rdx
  2c:	59                   	pop    %rcx
  2d:	c3                   	ret
  2e:	90                   	nop
  2f:	2e 8d b4 26 00 00 00 	cs lea 0x0(%rsi,%riz,1),%esi
  36:	00
  37:	8d b4 26 00 00 00 00 	lea    0x0(%rsi,%riz,1),%esi
  3e:	58                   	pop    %rax
  3f:	b8                   	.byte 0xb8

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/18 10:47 upstream 8541d8f725c6 5be7a9de .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-use-after-free Read in snd_pcm_action_single
* Struck through repros no longer work on HEAD.