Re: [syzbot] [usb?] KASAN: global-out-of-bounds Read in usb_copy_descriptors

[syzbot <syzbot+debc5c305403f180c01c@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    6c2cb8b8b843 Add linux-next specific files for 20260930
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1190e3f5580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6f425a2650355dac
dashboard link: https://syzkaller.appspot.com/bug?extid=debc5c305403f180c01c
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=112a43f5580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=152a43f5580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/d79eefc0c62e/disk-6c2cb8b8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d661335b4b7a/vmlinux-6c2cb8b8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e2aeb28cdc89/bzImage-6c2cb8b8.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+debc5c305403f180c01c@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: global-out-of-bounds in usb_copy_descriptors+0x1b8/0x320 drivers/usb/gadget/config.c:94
Read of size 128 at addr ffffffff9ad9cd80 by task syz-executor273/5627

CPU: 1 UID: 0 PID: 5627 Comm: syz-executor273 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_address_description+0x55/0x1e0 mm/kasan/report.c:378
 print_report+0x58/0x70 mm/kasan/report.c:482
 kasan_report+0x117/0x150 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:-1 [inline]
 kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200
 __asan_memcpy+0x29/0x70 mm/kasan/shadow.c:105
 usb_copy_descriptors+0x1b8/0x320 drivers/usb/gadget/config.c:94
 usb_assign_descriptors+0xcf/0x290 drivers/usb/gadget/config.c:131
 f_audio_bind+0x1b5e/0x34b0 drivers/usb/gadget/function/f_uac1.c:1443
 usb_add_function+0x2e1/0x9f0 drivers/usb/gadget/composite.c:333
 configfs_composite_bind+0xde0/0x1410 drivers/usb/gadget/configfs.c:1802
 gadget_bind_driver+0x2ca/0x9e0 drivers/usb/gadget/udc/core.c:1662
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x254/0xae0 drivers/base/dd.c:706
 __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:868
 driver_probe_device+0x4f/0x240 drivers/base/dd.c:898
 __driver_attach+0x339/0x600 drivers/base/dd.c:1292
 bus_for_each_dev+0x23b/0x2c0 drivers/base/bus.c:386
 bus_add_driver+0x38f/0x6e0 drivers/base/bus.c:771
 driver_register+0x23a/0x320 drivers/base/driver.c:174
 usb_gadget_register_driver_owner+0xf9/0x270 drivers/usb/gadget/udc/core.c:1752
 gadget_dev_desc_UDC_store+0x1c9/0x2f0 drivers/usb/gadget/configfs.c:300
 flush_write_buffer fs/configfs/file.c:207 [inline]
 configfs_write_iter+0x337/0x430 fs/configfs/file.c:229
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x612/0xba0 fs/read_write.c:687
 ksys_write+0x150/0x270 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc3b3d71df9
Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 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 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff154ebbf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000200000000400 RCX: 00007fc3b3d71df9
RDX: 000000000000000c RSI: 0000200000000480 RDI: 0000000000000003
RBP: 0000200000000000 R08: 0000555581694060 R09: 0000555581694060
R10: 0000555581694060 R11: 0000000000000246 R12: 00007fff154ebef8
R13: 0000000000000002 R14: 00007fff154ebc30 R15: 0000200000000008
 </TASK>

The buggy address belongs to the variable:
 ac_header_desc+0x0/0x20 f_uac1_legacy.c:-1

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1ad9c
flags: 0xfff00000002000(reserved|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000002000 ffffea00006b6708 ffffea00006b6708 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffffffff9ad9cc80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffff9ad9cd00: 00 00 00 00 00 00 00 00 00 00 00 00 f9 f9 f9 f9
>ffffffff9ad9cd80: 00 f9 f9 f9 00 f9 f9 f9 00 f9 f9 f9 00 00 f9 f9
                      ^
 ffffffff9ad9ce00: 00 00 f9 f9 00 00 f9 f9 00 00 f9 f9 00 00 00 00
 ffffffff9ad9ce80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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