[syzbot] [gfs2?] general protection fault in gfs2_quota_lock

[syzbot <syzbot+d84e35a320d14f8c270a@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    89c07d98716a Add linux-next specific files for 20260831
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=13eafe25580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3084bde934a7eb4b
dashboard link: https://syzkaller.appspot.com/bug?extid=d84e35a320d14f8c270a
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=167d3b79580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14c51379580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/efda3e96af9f/disk-89c07d98.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7cba3e147607/vmlinux-89c07d98.xz
kernel image: https://storage.googleapis.com/syzbot-assets/bf4b2e49d1cb/bzImage-89c07d98.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/85a2c905fb7a/mount_2.gz
  fsck result: OK (log: https://syzkaller.appspot.com/x/fsck.log?x=10c51379580000)

The issue was bisected to:

commit e65756f09826a87322479abc946ca11e6816a6ce
Author: Andreas Gruenbacher <agruenba@redhat.com>
Date:   Wed Aug 26 10:41:28 2026 +0000

    gfs2: No quotas for meta inodes

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=112f5c15580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=132f5c15580000
console output: https://syzkaller.appspot.com/x/log.txt?x=152f5c15580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d84e35a320d14f8c270a@syzkaller.appspotmail.com
Fixes: e65756f09826 ("gfs2: No quotas for meta inodes")

capability: warning: `syz-executor311' uses deprecated v2 capabilities in a way that may be insecure
Oops: general protection fault, probably for non-canonical address 0xdffffc0000000020: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000100-0x0000000000000107]
CPU: 1 UID: 0 PID: 5636 Comm: syz-executor311 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:gfs2_quota_lock+0x103/0x7b0 fs/gfs2/quota.c:1105
Code: 00 00 4d 89 fd 49 c1 ed 03 41 80 7c 1d 00 00 74 08 4c 89 ff e8 1e fd e7 fd 49 8b 3f 48 8d 87 00 01 00 00 48 89 c1 48 c1 e9 03 <0f> b6 0c 19 84 c9 0f 85 c9 05 00 00 8b b7 00 01 00 00 ba 08 00 00
RSP: 0018:ffffc90003bcf8d0 EFLAGS: 00010202
RAX: 0000000000000100 RBX: dffffc0000000000 RCX: 0000000000000020
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff907a487f R09: 1ffffffff20f490f
R10: dffffc0000000000 R11: fffffbfff20f4910 R12: ffff888012189320
R13: 1ffff110024312f9 R14: 00000000ffffffff R15: ffff8880121897c8
FS:  000055558edf6400(0000) GS:ffff888124dcd000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006a9ee0 CR3: 0000000073f60000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 gfs2_quota_lock_check fs/gfs2/quota.h:50 [inline]
 do_grow fs/gfs2/bmap.c:2117 [inline]
 gfs2_setattr_size+0x9df/0x1270 fs/gfs2/bmap.c:2198
 gfs2_setattr+0x269/0x430 fs/gfs2/inode.c:2138
 notify_change+0xbba/0xea0 fs/attr.c:556
 do_truncate+0x1c2/0x250 fs/open.c:68
 vfs_truncate+0x4b4/0x540 fs/open.c:118
 ksys_truncate+0xf3/0x1c0 fs/open.c:142
 __do_sys_truncate fs/open.c:154 [inline]
 __se_sys_truncate fs/open.c:152 [inline]
 __x64_sys_truncate+0x5b/0x70 fs/open.c:152
 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: 0033:0x7f49688f2409
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:00007ffd4cc3da68 EFLAGS: 00000246 ORIG_RAX: 000000000000004c
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 00007f49688f2409
RDX: 00007f49688f2409 RSI: 000000000008fff5 RDI: 0000200000000180
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffd4cc3db98
R13: 0000000000000002 R14: 00007f49689b3c80 R15: 0000000000000002
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:gfs2_quota_lock+0x103/0x7b0 fs/gfs2/quota.c:1105
Code: 00 00 4d 89 fd 49 c1 ed 03 41 80 7c 1d 00 00 74 08 4c 89 ff e8 1e fd e7 fd 49 8b 3f 48 8d 87 00 01 00 00 48 89 c1 48 c1 e9 03 <0f> b6 0c 19 84 c9 0f 85 c9 05 00 00 8b b7 00 01 00 00 ba 08 00 00
RSP: 0018:ffffc90003bcf8d0 EFLAGS: 00010202
RAX: 0000000000000100 RBX: dffffc0000000000 RCX: 0000000000000020
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: ffffffff907a487f R09: 1ffffffff20f490f
R10: dffffc0000000000 R11: fffffbfff20f4910 R12: ffff888012189320
R13: 1ffff110024312f9 R14: 00000000ffffffff R15: ffff8880121897c8
FS:  000055558edf6400(0000) GS:ffff888124dcd000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000006a9ee0 CR3: 0000000073f60000 CR4: 00000000003526f0
----------------
Code disassembly (best guess):
   0:	00 00                	add    %al,(%rax)
   2:	4d 89 fd             	mov    %r15,%r13
   5:	49 c1 ed 03          	shr    $0x3,%r13
   9:	41 80 7c 1d 00 00    	cmpb   $0x0,0x0(%r13,%rbx,1)
   f:	74 08                	je     0x19
  11:	4c 89 ff             	mov    %r15,%rdi
  14:	e8 1e fd e7 fd       	call   0xfde7fd37
  19:	49 8b 3f             	mov    (%r15),%rdi
  1c:	48 8d 87 00 01 00 00 	lea    0x100(%rdi),%rax
  23:	48 89 c1             	mov    %rax,%rcx
  26:	48 c1 e9 03          	shr    $0x3,%rcx
* 2a:	0f b6 0c 19          	movzbl (%rcx,%rbx,1),%ecx <-- trapping instruction
  2e:	84 c9                	test   %cl,%cl
  30:	0f 85 c9 05 00 00    	jne    0x5ff
  36:	8b b7 00 01 00 00    	mov    0x100(%rdi),%esi
  3c:	ba                   	.byte 0xba
  3d:	08 00                	or     %al,(%rax)


---
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