syzbot

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.0.17/4509 is trying to acquire lock:
ffff0000dce90ae0 (&sdp->sd_quota_mutex){+.+.}-{3:3}, at: do_qc+0xbc/0x648 fs/gfs2/quota.c:682

but task is already holding lock:
ffff0000e5b54fd0 (&ip->i_rw_mutex){++++}-{3:3}, at: sweep_bh_for_rgrps fs/gfs2/bmap.c:1512 [inline]
ffff0000e5b54fd0 (&ip->i_rw_mutex){++++}-{3:3}, at: punch_hole+0x20d8/0x2e88 fs/gfs2/bmap.c:1837

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+0x64/0x300 kernel/locking/rwsem.c:1520
       __gfs2_iomap_get+0x114/0x1044 fs/gfs2/bmap.c:856
       gfs2_iomap_get+0xd4/0x144 fs/gfs2/bmap.c:1396
       bh_get+0x1e4/0x604 fs/gfs2/quota.c:385
       qdsb_get+0x1d4/0x378 fs/gfs2/quota.c:522
       gfs2_quota_hold+0x16c/0x558 fs/gfs2/quota.c:608
       punch_hole+0xb74/0x2e88 fs/gfs2/bmap.c:1798
       gfs2_iomap_end+0x43c/0x608 fs/gfs2/bmap.c:1157
       iomap_iter+0x1d0/0x10e0 fs/iomap/iter.c:79
       iomap_file_buffered_write+0x5a0/0x6b8 fs/iomap/buffered-io.c:846
       gfs2_file_buffered_write+0x488/0x7e8 fs/gfs2/file.c:1057
       gfs2_file_write_iter+0x3f0/0xc1c fs/gfs2/file.c:1158
       __kernel_write_iter+0x208/0x56c fs/read_write.c:517
       dump_emit_page fs/coredump.c:950 [inline]
       dump_user_range+0x314/0x5e4 fs/coredump.c:977
       elf_core_dump+0x2880/0x2da0 fs/binfmt_elf.c:2354
       do_coredump+0x10cc/0x1c68 fs/coredump.c:824
       get_signal+0xdec/0x1304 kernel/signal.c:2857
       do_signal arch/arm64/kernel/signal.c:1095 [inline]
       do_notify_resume+0x28c/0x2aa4 arch/arm64/kernel/signal.c:1148
       prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
       exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
       el0_da+0xb4/0x144 arch/arm64/kernel/entry-common.c:516
       el0t_64_sync_handler+0x90/0xf0 arch/arm64/kernel/entry-common.c:658
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

-> #0 (&sdp->sd_quota_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3090 [inline]
       check_prevs_add kernel/locking/lockdep.c:3209 [inline]
       validate_chain kernel/locking/lockdep.c:3825 [inline]
       __lock_acquire+0x2880/0x6800 kernel/locking/lockdep.c:5049
       lock_acquire+0x20c/0x63c kernel/locking/lockdep.c:5662
       __mutex_lock_common+0x190/0x1f60 kernel/locking/mutex.c:603
       __mutex_lock kernel/locking/mutex.c:747 [inline]
       mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
       do_qc+0xbc/0x648 fs/gfs2/quota.c:682
       gfs2_quota_change+0x238/0x718 fs/gfs2/quota.c:1295
       punch_hole+0x2968/0x2e88 fs/gfs2/bmap.c:1938
       gfs2_iomap_end+0x43c/0x608 fs/gfs2/bmap.c:1157
       iomap_iter+0x1d0/0x10e0 fs/iomap/iter.c:79
       iomap_file_buffered_write+0x5a0/0x6b8 fs/iomap/buffered-io.c:846
       gfs2_file_buffered_write+0x488/0x7e8 fs/gfs2/file.c:1057
       gfs2_file_write_iter+0x3f0/0xc1c fs/gfs2/file.c:1158
       __kernel_write_iter+0x208/0x56c fs/read_write.c:517
       dump_emit_page fs/coredump.c:950 [inline]
       dump_user_range+0x314/0x5e4 fs/coredump.c:977
       elf_core_dump+0x2880/0x2da0 fs/binfmt_elf.c:2354
       do_coredump+0x10cc/0x1c68 fs/coredump.c:824
       get_signal+0xdec/0x1304 kernel/signal.c:2857
       do_signal arch/arm64/kernel/signal.c:1095 [inline]
       do_notify_resume+0x28c/0x2aa4 arch/arm64/kernel/signal.c:1148
       prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
       exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
       el0_da+0xb4/0x144 arch/arm64/kernel/entry-common.c:516
       el0t_64_sync_handler+0x90/0xf0 arch/arm64/kernel/entry-common.c:658
       el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

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 ***

5 locks held by syz.0.17/4509:
 #0: ffff0000d5064460 (sb_writers#12){.+.+}-{0:0}, at: do_coredump+0x10a8/0x1c68 fs/coredump.c:823
 #1: ffff0000e5b54b38 (&sb->s_type->i_mutex_key#20){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:758 [inline]
 #1: ffff0000e5b54b38 (&sb->s_type->i_mutex_key#20){+.+.}-{3:3}, at: gfs2_file_write_iter+0x2cc/0xc1c fs/gfs2/file.c:1115
 #2: ffff0000d5064650 (sb_internal#2){.+.+}-{0:0}, at: gfs2_trans_begin+0xa8/0x114 fs/gfs2/trans.c:118
 #3: ffff0000dce91058 (&sdp->sd_log_flush_lock){.+.+}-{3:3}, at: __gfs2_trans_begin+0x500/0x870 fs/gfs2/trans.c:87
 #4: ffff0000e5b54fd0 (&ip->i_rw_mutex){++++}-{3:3}, at: sweep_bh_for_rgrps fs/gfs2/bmap.c:1512 [inline]
 #4: ffff0000e5b54fd0 (&ip->i_rw_mutex){++++}-{3:3}, at: punch_hole+0x20d8/0x2e88 fs/gfs2/bmap.c:1837

stack backtrace:
CPU: 1 PID: 4509 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025
Call trace:
 dump_backtrace+0x1c0/0x1ec arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
 dump_stack+0x1c/0x5c lib/dump_stack.c:113
 print_circular_bug+0x148/0x1b0 kernel/locking/lockdep.c:2048
 check_noncircular+0x264/0x2f8 kernel/locking/lockdep.c:2170
 check_prev_add kernel/locking/lockdep.c:3090 [inline]
 check_prevs_add kernel/locking/lockdep.c:3209 [inline]
 validate_chain kernel/locking/lockdep.c:3825 [inline]
 __lock_acquire+0x2880/0x6800 kernel/locking/lockdep.c:5049
 lock_acquire+0x20c/0x63c kernel/locking/lockdep.c:5662
 __mutex_lock_common+0x190/0x1f60 kernel/locking/mutex.c:603
 __mutex_lock kernel/locking/mutex.c:747 [inline]
 mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
 do_qc+0xbc/0x648 fs/gfs2/quota.c:682
 gfs2_quota_change+0x238/0x718 fs/gfs2/quota.c:1295
 punch_hole+0x2968/0x2e88 fs/gfs2/bmap.c:1938
 gfs2_iomap_end+0x43c/0x608 fs/gfs2/bmap.c:1157
 iomap_iter+0x1d0/0x10e0 fs/iomap/iter.c:79
 iomap_file_buffered_write+0x5a0/0x6b8 fs/iomap/buffered-io.c:846
 gfs2_file_buffered_write+0x488/0x7e8 fs/gfs2/file.c:1057
 gfs2_file_write_iter+0x3f0/0xc1c fs/gfs2/file.c:1158
 __kernel_write_iter+0x208/0x56c fs/read_write.c:517
 dump_emit_page fs/coredump.c:950 [inline]
 dump_user_range+0x314/0x5e4 fs/coredump.c:977
 elf_core_dump+0x2880/0x2da0 fs/binfmt_elf.c:2354
 do_coredump+0x10cc/0x1c68 fs/coredump.c:824
 get_signal+0xdec/0x1304 kernel/signal.c:2857
 do_signal arch/arm64/kernel/signal.c:1095 [inline]
 do_notify_resume+0x28c/0x2aa4 arch/arm64/kernel/signal.c:1148
 prepare_exit_to_user_mode arch/arm64/kernel/entry-common.c:137 [inline]
 exit_to_user_mode arch/arm64/kernel/entry-common.c:142 [inline]
 el0_da+0xb4/0x144 arch/arm64/kernel/entry-common.c:516
 el0t_64_sync_handler+0x90/0xf0 arch/arm64/kernel/entry-common.c:658
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585