[v5.15] Internal error in fat_ioctl_filldir

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c79648372d02 Linux 5.15.189
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=108772f0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9e47345638b85bd0
dashboard link: https://syzkaller.appspot.com/bug?extid=882fe45f876e5615e624
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
userspace arch: arm64

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7ab49562317a/disk-c7964837.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/e847ec1e38d3/vmlinux-c7964837.xz
kernel image: https://storage.googleapis.com/syzbot-assets/263158c6371c/Image-c7964837.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+882fe4...@syzkaller.appspotmail.com

loop1: detected capacity change from 0 to 8192
Internal error: Oops - BTI: 0000000036000001 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 4272 Comm: syz.1.18 Not tainted 5.15.189-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
pstate: 42400405 (nZcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=jc)
pc : fat_ioctl_filldir+0x28c/0xdf4 fs/fat/dir.c:759
lr : fat_ioctl_filldir+0x268/0xdf4 fs/fat/dir.c:759
sp : ffff80001fcb7970
x29: ffff80001fcb79a0 x28: dfff800000000000 x27: 000000002000106a
x26: 1ffff00003f96f8b x25: 1fffe0001b4f5004 x24: ffff800011439b60
x23: 00000000fffffff2 x22: ffff0000da7a8024 x21: ffff0000da7a8000
x20: 0000002000106a00 x19: ffff80001fcb7c58 x18: 0000000000000000
x17: 0000000000000002 x16: ffff800008e3dc94 x15: 0000000082307202
x14: 0000000000ff0100 x13: 1ffff0000282e06b x12: 0000000000ff0100
x11: 0000000000000000 x10: 000000002000106a x9 : 0000ffffffffffff
x8 : 000000002000106a x7 : ffff800008750ed4 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000001
x2 : 0000000000000008 x1 : 0000000000000001 x0 : 0000000000000000
Call trace:
fat_ioctl_filldir+0x28c/0xdf4 fs/fat/dir.c:759
dir_emit_dotdot include/linux/fs.h:3722 [inline]
__fat_readdir+0xd64/0x132c fs/fat/dir.c:666
fat_ioctl_readdir fs/fat/dir.c:777 [inline]
fat_dir_ioctl+0x280/0x36c fs/fat/dir.c:815
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl fs/ioctl.c:860 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:860
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
el0_svc+0x78/0x1e0 arch/arm64/kernel/entry-common.c:608
el0t_64_sync_handler+0xcc/0xe4 arch/arm64/kernel/entry-common.c:626
el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584
Code: d503229f 2a1f03f7 2a1f03e0 38000957 (2a1703e1)
---[ end trace cfc040baf269c71e ]---
----------------
Code disassembly (best guess):
0: d503229f csdb
4: 2a1f03f7 mov w23, wzr
8: 2a1f03e0 mov w0, wzr
c: 38000957 sttrb w23, [x10]
* 10: 2a1703e1 mov w1, w23 <-- trapping instruction


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.