[v5.15] KASAN: null-ptr-deref Write in slot_put

[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=13301ba2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f3b1215b3cf4119f
dashboard link: https://syzkaller.appspot.com/bug?extid=bf261d37b05805fd7c89
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/fa511d2a8893/disk-c7964837.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f14b6c77bbb9/vmlinux-c7964837.xz
kernel image: https://storage.googleapis.com/syzbot-assets/388987ba15c6/bzImage-c7964837.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bf261d...@syzkaller.appspotmail.com

RBP: 00007f6f527a2e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6f52947128 R14: 00007f6f52947090 R15: 00007ffed8b650a8
</TASK>
==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: null-ptr-deref in test_and_clear_bit include/asm-generic/bitops/instrumented-atomic.h:83 [inline]
BUG: KASAN: null-ptr-deref in slot_put+0x104/0x1e0 fs/gfs2/quota.c:359
Write of size 8 at addr 0000000000000000 by task syz.1.2/4380

CPU: 0 PID: 4380 Comm: syz.1.2 Not tainted 5.15.189-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
__kasan_report mm/kasan/report.c:438 [inline]
kasan_report+0xd5/0x130 mm/kasan/report.c:451
check_region_inline mm/kasan/generic.c:-1 [inline]
kasan_check_range+0x27b/0x290 mm/kasan/generic.c:189
instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
test_and_clear_bit include/asm-generic/bitops/instrumented-atomic.h:83 [inline]
slot_put+0x104/0x1e0 fs/gfs2/quota.c:359
qdsb_put fs/gfs2/quota.c:534 [inline]
gfs2_quota_unhold+0x278/0x5d0 fs/gfs2/quota.c:652
gfs2_quota_lock+0x1c7/0x7d0 fs/gfs2/quota.c:1095
gfs2_quota_lock_check fs/gfs2/quota.h:50 [inline]
do_grow fs/gfs2/bmap.c:2065 [inline]
gfs2_setattr_size+0x357/0x810 fs/gfs2/bmap.c:2140
gfs2_setattr+0x252/0x400 fs/gfs2/inode.c:2006
notify_change+0xbcd/0xee0 fs/attr.c:505
do_truncate+0x197/0x220 fs/open.c:65
do_sys_ftruncate+0x31b/0x3d0 fs/open.c:193
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f6f5271fbe9
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:00007f6f50966038 EFLAGS: 00000246 ORIG_RAX: 000000000000004d
RAX: ffffffffffffffda RBX: 00007f6f52947090 RCX: 00007f6f5271fbe9
RDX: 0000000000000000 RSI: 000000000000c17a RDI: 0000000000000006
RBP: 00007f6f527a2e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6f52947128 R14: 00007f6f52947090 R15: 00007ffed8b650a8
</TASK>
==================================================================


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[syzbot]

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