syzbot

gfs2: fsid=syz:syz.0: found 1 quota changes
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.255/5659 is trying to acquire lock:
ffff88807b76cae0 (&sdp->sd_quota_mutex){+.+.}-{3:3}, at: do_qc+0xca/0x730 fs/gfs2/quota.c:678

but task is already holding lock:
ffff888073a0d748 (&ip->i_rw_mutex){++++}-{3:3}, at: __gfs2_iomap_alloc+0x271/0x1a20 fs/gfs2/bmap.c:681

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&ip->i_rw_mutex){++++}-{3:3}:
       down_read+0x44/0x2e0 kernel/locking/rwsem.c:1498
       __gfs2_iomap_get+0x155/0x13e0 fs/gfs2/bmap.c:858
       gfs2_iomap_get fs/gfs2/bmap.c:1398 [inline]
       gfs2_block_map+0x229/0x670 fs/gfs2/bmap.c:1213
       bh_get+0x227/0x5f0 fs/gfs2/quota.c:385
       qdsb_get+0x21c/0x3c0 fs/gfs2/quota.c:518
       gfs2_quota_hold+0x194/0x5d0 fs/gfs2/quota.c:604
       gfs2_quota_lock+0xa0/0x7d0 fs/gfs2/quota.c:1076
       gfs2_quota_lock_check fs/gfs2/quota.h:50 [inline]
       alloc_dinode+0x164/0x4f0 fs/gfs2/inode.c:402
       gfs2_create_inode+0xc22/0x13b0 fs/gfs2/inode.c:721
       gfs2_atomic_open+0xce/0x210 fs/gfs2/inode.c:1296
       atomic_open fs/namei.c:3325 [inline]
       lookup_open fs/namei.c:3433 [inline]
       open_last_lookups fs/namei.c:3532 [inline]
       path_openat+0xe6d/0x2f30 fs/namei.c:3739
       do_filp_open+0x1b3/0x3e0 fs/namei.c:3769
       do_sys_openat2+0x142/0x4a0 fs/open.c:1253
       do_sys_open fs/open.c:1269 [inline]
       __do_sys_openat fs/open.c:1285 [inline]
       __se_sys_openat fs/open.c:1280 [inline]
       __x64_sys_openat+0x135/0x160 fs/open.c:1280
       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

-> #0 (&sdp->sd_quota_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
       lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
       __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       do_qc+0xca/0x730 fs/gfs2/quota.c:678
       gfs2_quota_change+0x2f5/0x8e0 fs/gfs2/quota.c:1295
       gfs2_alloc_blocks+0x195e/0x2110 fs/gfs2/rgrp.c:2504
       __gfs2_iomap_alloc+0x4d1/0x1a20 fs/gfs2/bmap.c:707
       gfs2_iomap_begin_write fs/gfs2/bmap.c:1049 [inline]
       gfs2_iomap_begin+0xacf/0x1250 fs/gfs2/bmap.c:1114
       iomap_iter+0x620/0xdb0 fs/iomap/iter.c:74
       iomap_file_buffered_write+0x17e/0x5b0 fs/iomap/buffered-io.c:814
       gfs2_file_buffered_write+0x470/0x900 fs/gfs2/file.c:1058
       gfs2_file_write_iter+0x467/0x11d0 fs/gfs2/file.c:1166
       call_write_iter include/linux/fs.h:2172 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x712/0xd00 fs/read_write.c:594
       ksys_write+0x14d/0x250 fs/read_write.c:647
       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

other info that might help us debug this:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&ip->i_rw_mutex);
                               lock(&sdp->sd_quota_mutex);
                               lock(&ip->i_rw_mutex);
  lock(&sdp->sd_quota_mutex);

 *** DEADLOCK ***

6 locks held by syz.2.255/5659:
 #0: ffff88802b2b0ff0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2bf/0x370 fs/file.c:1056
 #1: ffff88807de8e460 (sb_writers#25){.+.+}-{0:0}, at: vfs_write+0x28a/0xd00 fs/read_write.c:590
 #2: ffff888073a0d2b0 (&sb->s_type->i_mutex_key#30){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:787 [inline]
 #2: ffff888073a0d2b0 (&sb->s_type->i_mutex_key#30){+.+.}-{3:3}, at: gfs2_file_write_iter+0x33b/0x11d0 fs/gfs2/file.c:1123
 #3: ffff88807de8e650 (sb_internal#6){.+.+}-{0:0}, at: gfs2_trans_begin+0x6b/0xe0 fs/gfs2/trans.c:118
 #4: ffff88807b76d0a8 (&sdp->sd_log_flush_lock){.+.+}-{3:3}, at: __gfs2_trans_begin+0x50f/0x880 fs/gfs2/trans.c:87
 #5: ffff888073a0d748 (&ip->i_rw_mutex){++++}-{3:3}, at: __gfs2_iomap_alloc+0x271/0x1a20 fs/gfs2/bmap.c:681

stack backtrace:
CPU: 1 PID: 5659 Comm: syz.2.255 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 check_noncircular+0x274/0x310 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2c33/0x7c60 kernel/locking/lockdep.c:5012
 lock_acquire+0x197/0x3f0 kernel/locking/lockdep.c:5623
 __mutex_lock_common+0x1eb/0x2390 kernel/locking/mutex.c:596
 __mutex_lock kernel/locking/mutex.c:729 [inline]
 mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
 do_qc+0xca/0x730 fs/gfs2/quota.c:678
 gfs2_quota_change+0x2f5/0x8e0 fs/gfs2/quota.c:1295
 gfs2_alloc_blocks+0x195e/0x2110 fs/gfs2/rgrp.c:2504
 __gfs2_iomap_alloc+0x4d1/0x1a20 fs/gfs2/bmap.c:707
 gfs2_iomap_begin_write fs/gfs2/bmap.c:1049 [inline]
 gfs2_iomap_begin+0xacf/0x1250 fs/gfs2/bmap.c:1114
 iomap_iter+0x620/0xdb0 fs/iomap/iter.c:74
 iomap_file_buffered_write+0x17e/0x5b0 fs/iomap/buffered-io.c:814
 gfs2_file_buffered_write+0x470/0x900 fs/gfs2/file.c:1058
 gfs2_file_write_iter+0x467/0x11d0 fs/gfs2/file.c:1166
 call_write_iter include/linux/fs.h:2172 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x712/0xd00 fs/read_write.c:594
 ksys_write+0x14d/0x250 fs/read_write.c:647
 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: 0033:0x7f1e0f1daba9
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:00007f1e0d442038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f1e0f421fa0 RCX: 00007f1e0f1daba9
RDX: 0000000000000e09 RSI: 0000200000000040 RDI: 000000000000000b
RBP: 00007f1e0f25de19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1e0f422038 R14: 00007f1e0f421fa0 R15: 00007fffa6bf6c68
 </TASK>
==================================================================
BUG: KASAN: stack-out-of-bounds in should_fault_in_pages fs/gfs2/file.c:785 [inline]
BUG: KASAN: stack-out-of-bounds in gfs2_file_buffered_write+0x576/0x900 fs/gfs2/file.c:1070
Read of size 8 at addr ffffc900036f7d50 by task syz.2.255/5659

CPU: 1 PID: 5659 Comm: syz.2.255 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 print_address_description+0x60/0x2d0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xdf/0x130 mm/kasan/report.c:451
 should_fault_in_pages fs/gfs2/file.c:785 [inline]
 gfs2_file_buffered_write+0x576/0x900 fs/gfs2/file.c:1070
 gfs2_file_write_iter+0x467/0x11d0 fs/gfs2/file.c:1166
 call_write_iter include/linux/fs.h:2172 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x712/0xd00 fs/read_write.c:594
 ksys_write+0x14d/0x250 fs/read_write.c:647
 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: 0033:0x7f1e0f1daba9
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:00007f1e0d442038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f1e0f421fa0 RCX: 00007f1e0f1daba9
RDX: 0000000000000e09 RSI: 0000200000000040 RDI: 000000000000000b
RBP: 00007f1e0f25de19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1e0f422038 R14: 00007f1e0f421fa0 R15: 00007fffa6bf6c68
 </TASK>


addr ffffc900036f7d50 is located in stack of task syz.2.255/5659 at offset 48 in frame:
 vfs_write+0x0/0xd00

this frame has 3 objects:
 [32, 48) 'iov.i'
 [64, 112) 'kiocb.i'
 [144, 184) 'iter.i'

Memory state around the buggy address:
 ffffc900036f7c00: f1 f1 f1 f1 00 00 00 00 00 00 00 f3 f3 f3 f3 f3
 ffffc900036f7c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc900036f7d00: 00 00 00 00 f1 f1 f1 f1 00 00 f2 f2 00 00 00 00
                                                 ^
 ffffc900036f7d80: 00 00 f2 f2 f2 f2 00 00 00 00 00 f3 f3 f3 f3 f3
 ffffc900036f7e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================