KASAN: slab-out-of-bounds Write in copy_to_urb (2)

Status: fixed on 2026/05/06 16:40
Subsystems: usb sound
[Documentation on labels]
Reported-by: syzbot+6db0415d6d5c635f72cb@syzkaller.appspotmail.com
Fix commit: ef5749ef8b30 ALSA: usb-audio: Prevent excessive number of frames
First crash: 196d, last: 195d
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[PATCH] ALSA: usb-audio: Prevent excessive number of frames 2 (2) 2026/01/13 14:06
[syzbot] [sound?] [usb?] KASAN: slab-out-of-bounds Write in copy_to_urb (2) 1 (3) 2026/01/13 08:15
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 KASAN: slab-out-of-bounds Write in copy_to_urb origin:lts-only 21 C done 7 238d 242d 3/3 fixed on 2026/01/11 15:32
linux-6.1 KASAN: slab-out-of-bounds Write in copy_to_urb (2) origin:lts-only 21 C inconclusive 7 160d 175d 0/3 upstream: reported C repro on 2026/01/31 10:36
linux-6.6 KASAN: slab-out-of-bounds Write in copy_to_urb origin:lts-only 21 C inconclusive 7 160d 243d 0/2 upstream: reported C repro on 2025/11/24 08:39
upstream KASAN: slab-out-of-bounds Write in copy_to_urb usb sound 21 C 33 202d 262d 29/29 fixed on 2026/01/07 12:29
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/01/13 07:54 20m eadavis@qq.com patch upstream OK log

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in copy_to_urb+0x261/0x460 sound/usb/pcm.c:1487
Write of size 264 at addr ffff88804337e800 by task syz.0.17/5506

CPU: 0 UID: 0 PID: 5506 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x2b0/0x2c0 mm/kasan/generic.c:200
 __asan_memcpy+0x40/0x70 mm/kasan/shadow.c:106
 copy_to_urb+0x261/0x460 sound/usb/pcm.c:1487
 prepare_playback_urb+0x953/0x13d0 sound/usb/pcm.c:1611
 prepare_outbound_urb+0x377/0xc50 sound/usb/endpoint.c:333
 snd_usb_endpoint_start+0x4db/0x1530 sound/usb/endpoint.c:1596
 start_endpoints+0xa1/0x280 sound/usb/pcm.c:291
 snd_usb_substream_playback_trigger+0x3e0/0x830 sound/usb/pcm.c:1711
 snd_pcm_do_start+0xb7/0x180 sound/core/pcm_native.c:1454
 snd_pcm_action_single sound/core/pcm_native.c:1310 [inline]
 snd_pcm_action+0xe7/0x240 sound/core/pcm_native.c:1393
 __snd_pcm_lib_xfer+0x1762/0x1d00 sound/core/pcm_lib.c:2405
 snd_pcm_oss_write3+0x1bc/0x350 sound/core/oss/pcm_oss.c:1241
 snd_pcm_plug_write_transfer+0x2cb/0x4c0 sound/core/oss/pcm_plugin.c:630
 snd_pcm_oss_write2 sound/core/oss/pcm_oss.c:1373 [inline]
 snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1439 [inline]
 snd_pcm_oss_write+0xa2b/0xf20 sound/core/oss/pcm_oss.c:2794
 vfs_write+0x27e/0xb30 fs/read_write.c:684
 ksys_write+0x145/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8ffad8f7c9
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:00007ffe0de78008 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f8ffafe5fa0 RCX: 00007f8ffad8f7c9
RDX: 00000000000005ce RSI: 0000200000000600 RDI: 0000000000000004
RBP: 00007f8ffae13f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8ffafe5fa0 R14: 00007f8ffafe5fa0 R15: 0000000000000003
 </TASK>

Allocated by task 5506:
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5657 [inline]
 __kmalloc_noprof+0x41d/0x800 mm/slub.c:5669
 data_ep_set_params sound/usb/endpoint.c:1242 [inline]
 snd_usb_endpoint_set_params+0x1741/0x2f10 sound/usb/endpoint.c:1379
 snd_usb_hw_params+0xb12/0x12e0 sound/usb/pcm.c:576
 snd_pcm_hw_params+0x89d/0x1d30 sound/core/pcm_native.c:804
 snd_pcm_oss_change_params_locked+0x21cd/0x3f70 sound/core/oss/pcm_oss.c:965
 snd_pcm_oss_make_ready_locked+0x7d/0x300 sound/core/oss/pcm_oss.c:1186
 snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1404 [inline]
 snd_pcm_oss_write+0x281/0xf20 sound/core/oss/pcm_oss.c:2794
 vfs_write+0x27e/0xb30 fs/read_write.c:684
 ksys_write+0x145/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88804337e800
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 0 bytes inside of
 allocated 240-byte region [ffff88804337e800, ffff88804337e8f0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4337e
ksm flags: 0x4fff00000000000(node=1|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 04fff00000000000 ffff88801a441b40 ffffea000158d7c0 dead000000000003
raw: 0000000000000000 0000000000080008 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 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 5368, tgid 5368 (syz-executor), ts 97563098162, free_ts 97561893679
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x234/0x290 mm/page_alloc.c:1857
 prep_new_page mm/page_alloc.c:1865 [inline]
 get_page_from_freelist+0x24e0/0x2580 mm/page_alloc.c:3915
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5210
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2486
 alloc_slab_page mm/slub.c:3075 [inline]
 allocate_slab+0x86/0x3b0 mm/slub.c:3248
 new_slab mm/slub.c:3302 [inline]
 ___slab_alloc+0xe53/0x1820 mm/slub.c:4656
 __slab_alloc+0x65/0x100 mm/slub.c:4779
 __slab_alloc_node mm/slub.c:4855 [inline]
 slab_alloc_node mm/slub.c:5251 [inline]
 __kmalloc_cache_noprof+0x41e/0x700 mm/slub.c:5771
 kmalloc_noprof include/linux/slab.h:957 [inline]
 tc_action_net_init include/net/act_api.h:162 [inline]
 tunnel_key_init_net+0x65/0x190 net/sched/act_tunnel_key.c:849
 ops_init+0x35c/0x5c0 net/core/net_namespace.c:137
 setup_net+0x110/0x330 net/core/net_namespace.c:446
 copy_net_ns+0x3e3/0x570 net/core/net_namespace.c:581
 create_new_namespaces+0x3e7/0x6a0 kernel/nsproxy.c:130
 unshare_nsproxy_namespaces+0x11c/0x170 kernel/nsproxy.c:226
 ksys_unshare+0x4c8/0x8c0 kernel/fork.c:3171
 __do_sys_unshare kernel/fork.c:3242 [inline]
 __se_sys_unshare kernel/fork.c:3240 [inline]
 __x64_sys_unshare+0x38/0x50 kernel/fork.c:3240
page last free pid 4584 tgid 4584 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1406 [inline]
 __free_frozen_pages+0xbc8/0xd30 mm/page_alloc.c:2943
 vfree+0x25a/0x400 mm/vmalloc.c:3466
 __ebt_unregister_table+0x531/0x600 net/bridge/netfilter/ebtables.c:1176
 ops_exit_list net/core/net_namespace.c:199 [inline]
 ops_undo_list+0x49a/0x990 net/core/net_namespace.c:252
 cleanup_net+0x4d8/0x7a0 net/core/net_namespace.c:696
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

Memory state around the buggy address:
 ffff88804337e780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88804337e800: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88804337e880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc fc
                                                             ^
 ffff88804337e900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88804337e980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/11 05:09 upstream 54e82e93ca93 d1b870e1 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Write in copy_to_urb
2026/01/11 04:10 upstream 54e82e93ca93 d1b870e1 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Write in copy_to_urb
2026/01/11 03:07 upstream 54e82e93ca93 d1b870e1 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Write in copy_to_urb
2026/01/11 02:03 upstream 54e82e93ca93 d1b870e1 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Write in copy_to_urb
2026/01/11 00:59 upstream 54e82e93ca93 d1b870e1 .config console log report [disk image (non-bootable)] [vmlinux] [kernel image] ci-snapshot-upstream-root KASAN: slab-out-of-bounds Write in copy_to_urb
* Struck through repros no longer work on HEAD.