Message-ID: <690b6b46.050a0220.3d0d33.0054.GAE@google.com>
Date: Wed, 05 Nov 2025 07:20:38 -0800
From: syzbot <syzbot+bfd77469c8966de076f7@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, linux-sound@...r.kernel.org, 
	linux-usb@...r.kernel.org, perex@...ex.cz, syzkaller-bugs@...glegroups.com, 
	tiwai@...e.com
Subject: [syzbot] [sound?] [usb?] KASAN: slab-out-of-bounds Write in copy_to_urb

Hello,

syzbot found the following issue on:

HEAD commit:    ba36dd5ee6fd Merge tag 'bpf-fixes' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1759afe2580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=929790bc044e87d7
dashboard link: https://syzkaller.appspot.com/bug?extid=bfd77469c8966de076f7
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11c74292580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=107bffe2580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-ba36dd5e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f3d081e7b0db/vmlinux-ba36dd5e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/612c239b909b/bzImage-ba36dd5e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bfd77469c8966de076f7@...kaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in copy_to_urb+0x261/0x460 sound/usb/pcm.c:1487
Write of size 264 at addr ffff88801107b400 by task syz.0.17/5461

CPU: 0 UID: 0 PID: 5461 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+0x189/0x250 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+0x4d8/0x14a0 sound/usb/endpoint.c:1591
 start_endpoints+0xa1/0x280 sound/usb/pcm.c:291
 snd_usb_substream_playback_trigger+0x3e0/0x7a0 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+0x1762/0x1ce0 sound/core/pcm_lib.c:2405
 snd_pcm_oss_write3+0x1bc/0x320 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+0xb9c/0x1190 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+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff91798efc9
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:00007ffee4c24fc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007ff917be5fa0 RCX: 00007ff91798efc9
RDX: 00000000000005ce RSI: 0000200000000e00 RDI: 0000000000000004
RBP: 00007ff917a11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff917be5fa0 R14: 00007ff917be5fa0 R15: 0000000000000003
 </TASK>

Allocated by task 5461:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 poison_kmalloc_redzone mm/kasan/common.c:400 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:417
 kasan_kmalloc include/linux/kasan.h:262 [inline]
 __do_kmalloc_node mm/slub.c:5642 [inline]
 __kmalloc_noprof+0x411/0x7f0 mm/slub.c:5654
 data_ep_set_params sound/usb/endpoint.c:1242 [inline]
 snd_usb_endpoint_set_params+0x1610/0x29a0 sound/usb/endpoint.c:1374
 snd_usb_hw_params+0xb12/0x1280 sound/usb/pcm.c:576
 snd_pcm_hw_params+0x89d/0x1d30 sound/core/pcm_native.c:804
 snd_pcm_oss_change_params_locked+0x21cb/0x3e40 sound/core/oss/pcm_oss.c:965
 snd_pcm_oss_make_ready_locked sound/core/oss/pcm_oss.c:1186 [inline]
 snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1404 [inline]
 snd_pcm_oss_write+0x2fb/0x1190 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+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88801107b400
 which belongs to the cache kmalloc-64 of size 64
The buggy address is located 0 bytes inside of
 allocated 54-byte region [ffff88801107b400, ffff88801107b436)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1107b
anon flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801a0418c0 ffffea000045fc80 dead000000000005
raw: 0000000000000000 0000000080200020 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 0x52c40(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 5341, tgid 5341 (syz-executor), ts 97923846546, free_ts 97738761799
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1850
 prep_new_page mm/page_alloc.c:1858 [inline]
 get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3884
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5183
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
 alloc_slab_page mm/slub.c:3055 [inline]
 allocate_slab+0x96/0x350 mm/slub.c:3228
 new_slab mm/slub.c:3282 [inline]
 ___slab_alloc+0xe94/0x18a0 mm/slub.c:4651
 __slab_alloc+0x65/0x100 mm/slub.c:4770
 __slab_alloc_node mm/slub.c:4846 [inline]
 slab_alloc_node mm/slub.c:5268 [inline]
 __do_kmalloc_node mm/slub.c:5641 [inline]
 __kmalloc_noprof+0x471/0x7f0 mm/slub.c:5654
 kmalloc_noprof include/linux/slab.h:961 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 tomoyo_encode2 security/tomoyo/realpath.c:45 [inline]
 tomoyo_encode+0x28b/0x550 security/tomoyo/realpath.c:80
 tomoyo_realpath_from_path+0x58d/0x5d0 security/tomoyo/realpath.c:283
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_check_open_permission+0x1c1/0x3b0 security/tomoyo/file.c:771
 security_file_open+0xb1/0x270 security/security.c:3183
 do_dentry_open+0x384/0x13f0 fs/open.c:942
 vfs_open+0x3b/0x340 fs/open.c:1097
 do_open fs/namei.c:3975 [inline]
 path_openat+0x2ee5/0x3830 fs/namei.c:4134
 do_filp_open+0x1fa/0x410 fs/namei.c:4161
page last free pid 5331 tgid 5331 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1394 [inline]
 __free_frozen_pages+0xbc4/0xd30 mm/page_alloc.c:2906
 vfree+0x25a/0x400 mm/vmalloc.c:3440
 kcov_put kernel/kcov.c:439 [inline]
 kcov_close+0x28/0x50 kernel/kcov.c:535
 __fput+0x44c/0xa70 fs/file_table.c:468
 task_work_run+0x1d4/0x260 kernel/task_work.c:227
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x6b5/0x2300 kernel/exit.c:966
 do_group_exit+0x21c/0x2d0 kernel/exit.c:1107
 get_signal+0x1285/0x1340 kernel/signal.c:3034
 arch_do_signal_or_restart+0xa0/0x790 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x72/0x130 kernel/entry/common.c:40
 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+0x2bd/0xfa0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88801107b300: 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc
 ffff88801107b380: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
>ffff88801107b400: 00 00 00 00 00 00 06 fc fc fc fc fc fc fc fc fc
                                     ^
 ffff88801107b480: 00 00 00 00 00 00 06 fc fc fc fc fc fc fc fc fc
 ffff88801107b500: fa fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
==================================================================


---
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