[Android 5.10] general protection fault in fsg_common_set_num_buffers

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 452567d1985b Revert "HID: input: read battery capacity fro..
git tree: android13-5.10-lts
console+strace: https://syzkaller.appspot.com/x/log.txt?x=179d9c5e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=57bdfa4a173e5087
dashboard link: https://syzkaller.appspot.com/bug?extid=f50543928799ebe66212
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=10d0a2c9580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14d0a2c9580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9268e34b0c5f/disk-452567d1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7237143009db/vmlinux-452567d1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2921bc70b2f7/bzImage-452567d1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f50543...@syzkaller.appspotmail.com

LUN: removable file: (no medium)
general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
CPU: 1 PID: 297 Comm: syz-executor100 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:fsg_common_set_num_buffers+0x65/0x2b0 drivers/usb/gadget/function/f_mass_storage.c:2649
Code: 89 c6 49 bd 00 00 00 00 00 fc ff df bf 00 40 00 00 be c0 0c 00 00 ba 02 00 00 00 e8 25 cb 81 fe 48 89 c3 4c 89 f0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 f7 e8 6c f4 8e fe 49 89 1e 48 85 db 0f
RSP: 0018:ffffc90000b27b28 EFLAGS: 00010202
RAX: 0000000000000002 RBX: ffff88810b430000 RCX: 0000000000000002
RDX: 0000000000000000 RSI: ffffffff8310419b RDI: ffffed1021686800
RBP: ffffc90000b27b70 R08: 0000000000004000 R09: ffffed1021686800
R10: dffffc0000000000 R11: fffffbfff0c81a7f R12: ffff88810abbc400
R13: dffffc0000000000 R14: 0000000000000010 R15: 0000000000000000
FS: 000055555e1b23c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f25fc263008 CR3: 00000001081b0000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
fsg_opts_num_buffers_store+0x138/0x1c0 drivers/usb/gadget/function/f_mass_storage.c:3329
flush_write_buffer fs/configfs/file.c:251 [inline]
configfs_write_file+0x320/0x3d0 fs/configfs/file.c:283
vfs_write+0x344/0xd70 fs/read_write.c:603
ksys_write+0x14a/0x260 fs/read_write.c:658
__do_sys_write fs/read_write.c:670 [inline]
__se_sys_write fs/read_write.c:667 [inline]
__x64_sys_write+0x7b/0x90 fs/read_write.c:667
do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f25fc1c6ef9
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:00007fff0666b668 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000200000000300 RCX: 00007f25fc1c6ef9
RDX: 0000000000000012 RSI: 0000200000000300 RDI: 0000000000000003
RBP: 6769666e6f632f2e R08: 000000000000000f R09: 00007fff0666b7a8
R10: 0000000000000001 R11: 0000000000000246 R12: 00007fff0666b798
R13: 0000000000000002 R14: 0000200000000008 R15: 0000000000000002
Modules linked in:
---[ end trace fa641a437428012b ]---
RIP: 0010:fsg_common_set_num_buffers+0x65/0x2b0 drivers/usb/gadget/function/f_mass_storage.c:2649
Code: 89 c6 49 bd 00 00 00 00 00 fc ff df bf 00 40 00 00 be c0 0c 00 00 ba 02 00 00 00 e8 25 cb 81 fe 48 89 c3 4c 89 f0 48 c1 e8 03 <42> 80 3c 28 00 74 08 4c 89 f7 e8 6c f4 8e fe 49 89 1e 48 85 db 0f
RSP: 0018:ffffc90000b27b28 EFLAGS: 00010202
RAX: 0000000000000002 RBX: ffff88810b430000 RCX: 0000000000000002
RDX: 0000000000000000 RSI: ffffffff8310419b RDI: ffffed1021686800
RBP: ffffc90000b27b70 R08: 0000000000004000 R09: ffffed1021686800
R10: dffffc0000000000 R11: fffffbfff0c81a7f R12: ffff88810abbc400
R13: dffffc0000000000 R14: 0000000000000010 R15: 0000000000000000
FS: 000055555e1b23c0(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f25fc263008 CR3: 00000001081b0000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
----------------
Code disassembly (best guess):
0: 89 c6 mov %eax,%esi
2: 49 bd 00 00 00 00 00 movabs $0xdffffc0000000000,%r13
9: fc ff df
c: bf 00 40 00 00 mov $0x4000,%edi
11: be c0 0c 00 00 mov $0xcc0,%esi
16: ba 02 00 00 00 mov $0x2,%edx
1b: e8 25 cb 81 fe call 0xfe81cb45
20: 48 89 c3 mov %rax,%rbx
23: 4c 89 f0 mov %r14,%rax
26: 48 c1 e8 03 shr $0x3,%rax
* 2a: 42 80 3c 28 00 cmpb $0x0,(%rax,%r13,1) <-- trapping instruction
2f: 74 08 je 0x39
31: 4c 89 f7 mov %r14,%rdi
34: e8 6c f4 8e fe call 0xfe8ef4a5
39: 49 89 1e mov %rbx,(%r14)
3c: 48 85 db test %rbx,%rbx
3f: 0f .byte 0xf


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