[syzbot] [sound?] [usb?] KASAN: slab-out-of-bounds Write in copy_to_urb (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 54e82e93ca93 Merge tag 'core_urgent_for_v6.19_rc4' of git:..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17467f92580000
kernel config: https://syzkaller.appspot.com/x/.config?x=513255d80ab78f2b
dashboard link: https://syzkaller.appspot.com/bug?extid=6db0415d6d5c635f72cb
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=17e4d922580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10c67f92580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-54e82e93.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f3befb5f53a4/vmlinux-54e82e93.xz
kernel image: https://storage.googleapis.com/syzbot-assets/92820ca1dbd8/bzImage-54e82e93.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6db041...@syzkaller.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 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
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

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If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
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If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Edward Adam Davis]

#syz test

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index 54d01dfd820f..263abb36bb2d 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -1553,7 +1553,7 @@ static int prepare_playback_urb(struct snd_usb_substream *subs,

for (i = 0; i < ctx->packets; i++) {
counts = snd_usb_endpoint_next_packet_size(ep, ctx, i, avail);
- if (counts < 0)
+ if (counts < 0 || frames + counts >= ep->max_urb_frames)
break;
/* set up descriptor */
urb->iso_frame_desc[i].offset = frames * stride;

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+6db041...@syzkaller.appspotmail.com
Tested-by: syzbot+6db041...@syzkaller.appspotmail.com

Tested on:

commit: b71e635f Merge tag 'cgroup-for-6.19-rc5-fixes' of git:..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14fb05fc580000
kernel config: https://syzkaller.appspot.com/x/.config?x=3027d9a5f96d82ca

dashboard link: https://syzkaller.appspot.com/bug?extid=6db0415d6d5c635f72cb
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

patch: https://syzkaller.appspot.com/x/patch.diff?x=1340699a580000

Note: testing is done by a robot and is best-effort only.

[Edward Adam Davis]

In this case, the user constructed the parameters with maxpacksize 40
for rate 22050 / pps 1000, and packsize[0] 22 packsize[1] 23. The buffer
size for each data URB is maxpacksize * packets, which in this example
is 40 * 6 = 240; When the user performs a write operation to send audio
data into the ALSA PCM playback stream, the calculated number of frames
is packsize[0] * packets = 264, which exceeds the allocated URB buffer
size, triggering the out-of-bounds (OOB) issue reported by syzbot [1].

Added a check for the number of single data URB frames when calculating
the number of frames to prevent [1].

[1]

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

Call Trace:

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

Reported-by: syzbot+6db041...@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=6db0415d6d5c635f72cb
Tested-by: syzbot+6db041...@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <ead...@qq.com>
---
sound/usb/pcm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--
2.43.0