syzbot


possible deadlock in ext4_buffered_write_iter

Status: upstream: reported on 2024/10/24 18:24
Reported-by: syzbot+7bd750844d6009cfebea@syzkaller.appspotmail.com
First crash: 45d, last: 45d

Sample crash report:
EXT4-fs (loop1): mounted filesystem without journal. Opts: bsdgroups,,errors=continue. Quota mode: none.
======================================================
WARNING: possible circular locking dependency detected
5.15.169-syzkaller #0 Not tainted
------------------------------------------------------
syz.1.508/6152 is trying to acquire lock:
ffff8880780f8128 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock+0x1c/0x50 include/linux/mmap_lock.h:117

but task is already holding lock:
ffff8880733e0de8 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock include/linux/fs.h:789 [inline]
ffff8880733e0de8 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: ext4_buffered_write_iter+0xa0/0x360 fs/ext4/file.c:262

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #6 (&sb->s_type->i_mutex_key#9){++++}-{3:3}:
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
       down_read+0x45/0x2e0 kernel/locking/rwsem.c:1498
       inode_lock_shared include/linux/fs.h:799 [inline]
       ext4_bmap+0x4b/0x410 fs/ext4/inode.c:3163
       bmap+0xa1/0xd0 fs/inode.c:1795
       jbd2_journal_bmap fs/jbd2/journal.c:981 [inline]
       __jbd2_journal_erase fs/jbd2/journal.c:1796 [inline]
       jbd2_journal_flush+0x7a2/0xc90 fs/jbd2/journal.c:2502
       ext4_ioctl_checkpoint fs/ext4/ioctl.c:849 [inline]
       __ext4_ioctl fs/ext4/ioctl.c:1267 [inline]
       ext4_ioctl+0x3249/0x5b80 fs/ext4/ioctl.c:1276
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:874 [inline]
       __se_sys_ioctl+0xf1/0x160 fs/ioctl.c:860
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #5 (&journal->j_checkpoint_mutex){+.+.}-{3:3}:
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
       __mutex_lock_common+0x1da/0x25a0 kernel/locking/mutex.c:596
       mutex_lock_io_nested+0x45/0x60 kernel/locking/mutex.c:777
       jbd2_journal_flush+0x290/0xc90 fs/jbd2/journal.c:2474
       __ocfs2_flush_truncate_log+0x309/0x11c0 fs/ocfs2/alloc.c:6021
       ocfs2_flush_truncate_log+0x4b/0x60 fs/ocfs2/alloc.c:6067
       ocfs2_sync_fs+0x121/0x380 fs/ocfs2/super.c:403
       sync_filesystem+0x1bc/0x220 fs/sync.c:66
       generic_shutdown_super+0x6b/0x310 fs/super.c:448
       kill_block_super+0x7a/0xe0 fs/super.c:1427
       deactivate_locked_super+0xa0/0x110 fs/super.c:335
       cleanup_mnt+0x44e/0x500 fs/namespace.c:1143
       task_work_run+0x129/0x1a0 kernel/task_work.c:188
       tracehook_notify_resume include/linux/tracehook.h:189 [inline]
       exit_to_user_mode_loop+0x106/0x130 kernel/entry/common.c:181
       exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:214
       __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
       syscall_exit_to_user_mode+0x5d/0x240 kernel/entry/common.c:307
       do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:86
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #4 (&journal->j_barrier){+.+.}-{3:3}:
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
       __mutex_lock_common+0x1da/0x25a0 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       jbd2_journal_lock_updates+0x2aa/0x370 fs/jbd2/transaction.c:905
       __ocfs2_flush_truncate_log+0x2e7/0x11c0 fs/ocfs2/alloc.c:6020
       ocfs2_flush_truncate_log+0x4b/0x60 fs/ocfs2/alloc.c:6067
       ocfs2_sync_fs+0x121/0x380 fs/ocfs2/super.c:403
       sync_filesystem+0x1bc/0x220 fs/sync.c:66
       generic_shutdown_super+0x6b/0x310 fs/super.c:448
       kill_block_super+0x7a/0xe0 fs/super.c:1427
       deactivate_locked_super+0xa0/0x110 fs/super.c:335
       cleanup_mnt+0x44e/0x500 fs/namespace.c:1143
       task_work_run+0x129/0x1a0 kernel/task_work.c:188
       tracehook_notify_resume include/linux/tracehook.h:189 [inline]
       exit_to_user_mode_loop+0x106/0x130 kernel/entry/common.c:181
       exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:214
       __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
       syscall_exit_to_user_mode+0x5d/0x240 kernel/entry/common.c:307
       do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:86
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #3 (&ocfs2_sysfile_lock_key[args->fi_sysfile_type]#6){+.+.}-{3:3}:
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
       down_write+0x38/0x60 kernel/locking/rwsem.c:1551
       inode_lock include/linux/fs.h:789 [inline]
       ocfs2_remove_btree_range+0x733/0x18a0 fs/ocfs2/alloc.c:5735
       ocfs2_remove_inode_range+0xd75/0x2640 fs/ocfs2/file.c:1899
       ocfs2_reflink_remap_extent fs/ocfs2/refcounttree.c:4571 [inline]
       ocfs2_reflink_remap_blocks+0xccf/0x1f20 fs/ocfs2/refcounttree.c:4718
       ocfs2_remap_file_range+0x5f2/0x8d0 fs/ocfs2/file.c:2691
       vfs_copy_file_range+0xfc9/0x14e0 fs/read_write.c:1510
       __do_sys_copy_file_range fs/read_write.c:1588 [inline]
       __se_sys_copy_file_range+0x3ea/0x5d0 fs/read_write.c:1551
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #2 (&oi->ip_alloc_sem){++++}-{3:3}:
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
       down_write+0x38/0x60 kernel/locking/rwsem.c:1551
       ocfs2_page_mkwrite+0x301/0xbd0 fs/ocfs2/mmap.c:142
       do_page_mkwrite+0x1a9/0x440 mm/memory.c:2909
       do_shared_fault mm/memory.c:4315 [inline]
       do_fault mm/memory.c:4383 [inline]
       handle_pte_fault mm/memory.c:4637 [inline]
       __handle_mm_fault mm/memory.c:4772 [inline]
       handle_mm_fault+0x2803/0x5960 mm/memory.c:4870
       do_user_addr_fault arch/x86/mm/fault.c:1357 [inline]
       handle_page_fault arch/x86/mm/fault.c:1445 [inline]
       exc_page_fault+0x271/0x700 arch/x86/mm/fault.c:1501
       asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606

-> #1 (sb_pagefaults#3){.+.+}-{0:0}:
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
       percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
       __sb_start_write include/linux/fs.h:1813 [inline]
       sb_start_pagefault include/linux/fs.h:1912 [inline]
       ocfs2_page_mkwrite+0x1d9/0xbd0 fs/ocfs2/mmap.c:122
       do_page_mkwrite+0x1a9/0x440 mm/memory.c:2909
       do_shared_fault mm/memory.c:4315 [inline]
       do_fault mm/memory.c:4383 [inline]
       handle_pte_fault mm/memory.c:4637 [inline]
       __handle_mm_fault mm/memory.c:4772 [inline]
       handle_mm_fault+0x2803/0x5960 mm/memory.c:4870
       do_user_addr_fault arch/x86/mm/fault.c:1357 [inline]
       handle_page_fault arch/x86/mm/fault.c:1445 [inline]
       exc_page_fault+0x271/0x700 arch/x86/mm/fault.c:1501
       asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606

-> #0 (&mm->mmap_lock){++++}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain+0x1649/0x5930 kernel/locking/lockdep.c:3788
       __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
       lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
       down_read+0x45/0x2e0 kernel/locking/rwsem.c:1498
       mmap_read_lock+0x1c/0x50 include/linux/mmap_lock.h:117
       do_user_addr_fault arch/x86/mm/fault.c:1308 [inline]
       handle_page_fault arch/x86/mm/fault.c:1445 [inline]
       exc_page_fault+0x596/0x700 arch/x86/mm/fault.c:1501
       asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
       __get_user_nocheck_1+0x6/0x10 arch/x86/lib/getuser.S:103
       fault_in_readable+0x172/0x2e0 mm/gup.c:1801
       fault_in_iov_iter_readable+0x14a/0x1d0 lib/iov_iter.c:460
       generic_perform_write+0x1c9/0x5b0 mm/filemap.c:3775
       ext4_buffered_write_iter+0x227/0x360 fs/ext4/file.c:268
       ext4_file_write_iter+0x1d1/0x1940 fs/ext4/file.c:662
       call_write_iter include/linux/fs.h:2174 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0xacd/0xe50 fs/read_write.c:594
       ksys_write+0x1a2/0x2c0 fs/read_write.c:647
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Chain exists of:
  &mm->mmap_lock --> &journal->j_checkpoint_mutex --> &sb->s_type->i_mutex_key#9

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sb->s_type->i_mutex_key#9);
                               lock(&journal->j_checkpoint_mutex);
                               lock(&sb->s_type->i_mutex_key#9);
  lock(&mm->mmap_lock);

 *** DEADLOCK ***

3 locks held by syz.1.508/6152:
 #0: ffff888076f26ff0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2cb/0x380 fs/file.c:1057
 #1: ffff88807404c460 (sb_writers#5){.+.+}-{0:0}, at: vfs_write+0x29a/0xe50 fs/read_write.c:590
 #2: ffff8880733e0de8 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: inode_lock include/linux/fs.h:789 [inline]
 #2: ffff8880733e0de8 (&sb->s_type->i_mutex_key#9){++++}-{3:3}, at: ext4_buffered_write_iter+0xa0/0x360 fs/ext4/file.c:262

stack backtrace:
CPU: 0 PID: 6152 Comm: syz.1.508 Not tainted 5.15.169-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
 check_noncircular+0x2f8/0x3b0 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+0x1649/0x5930 kernel/locking/lockdep.c:3788
 __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
 lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
 down_read+0x45/0x2e0 kernel/locking/rwsem.c:1498
 mmap_read_lock+0x1c/0x50 include/linux/mmap_lock.h:117
 do_user_addr_fault arch/x86/mm/fault.c:1308 [inline]
 handle_page_fault arch/x86/mm/fault.c:1445 [inline]
 exc_page_fault+0x596/0x700 arch/x86/mm/fault.c:1501
 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
RIP: 0010:__get_user_nocheck_1+0x6/0x10 arch/x86/lib/getuser.S:124
Code: d0 73 64 48 19 d2 48 21 d0 0f 01 cb 48 8b 10 31 c0 0f 01 ca c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 0f 01 cb 0f ae e8 <0f> b6 10 31 c0 0f 01 ca c3 90 0f 01 cb 0f ae e8 0f b7 10 31 c0 0f
RSP: 0018:ffffc90003087858 EFLAGS: 00050287
RAX: 0000000020321000 RBX: 0000000020320400 RCX: 0000000000040000
RDX: ffffc900061a1000 RSI: 000000000003ffff RDI: 0000000000040000
RBP: ffffc90003087918 R08: ffffffff81b743a6 R09: fffffbfff1bd2cb6
R10: 0000000000000000 R11: dffffc0000000001 R12: 00000000ffffffff
R13: 0000000020321000 R14: 0000000020322000 R15: 0000000000000000
 fault_in_readable+0x172/0x2e0 mm/gup.c:1801
 fault_in_iov_iter_readable+0x14a/0x1d0 lib/iov_iter.c:460
 generic_perform_write+0x1c9/0x5b0 mm/filemap.c:3775
 ext4_buffered_write_iter+0x227/0x360 fs/ext4/file.c:268
 ext4_file_write_iter+0x1d1/0x1940 fs/ext4/file.c:662
 call_write_iter include/linux/fs.h:2174 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0xacd/0xe50 fs/read_write.c:594
 ksys_write+0x1a2/0x2c0 fs/read_write.c:647
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fce59119ff9
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:00007fce57592038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fce592d1f80 RCX: 00007fce59119ff9
RDX: 000000000208e24b RSI: 0000000020001400 RDI: 0000000000000005
RBP: 00007fce5918c296 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fce592d1f80 R15: 00007ffc8bac1ce8
 </TASK>
----------------
Code disassembly (best guess):
   0:	d0 73 64             	shlb   0x64(%rbx)
   3:	48 19 d2             	sbb    %rdx,%rdx
   6:	48 21 d0             	and    %rdx,%rax
   9:	0f 01 cb             	stac
   c:	48 8b 10             	mov    (%rax),%rdx
   f:	31 c0                	xor    %eax,%eax
  11:	0f 01 ca             	clac
  14:	c3                   	ret
  15:	66 2e 0f 1f 84 00 00 	cs nopw 0x0(%rax,%rax,1)
  1c:	00 00 00
  1f:	0f 1f 44 00 00       	nopl   0x0(%rax,%rax,1)
  24:	0f 01 cb             	stac
  27:	0f ae e8             	lfence
* 2a:	0f b6 10             	movzbl (%rax),%edx <-- trapping instruction
  2d:	31 c0                	xor    %eax,%eax
  2f:	0f 01 ca             	clac
  32:	c3                   	ret
  33:	90                   	nop
  34:	0f 01 cb             	stac
  37:	0f ae e8             	lfence
  3a:	0f b7 10             	movzwl (%rax),%edx
  3d:	31 c0                	xor    %eax,%eax
  3f:	0f                   	.byte 0xf

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/10/24 18:24 linux-5.15.y 74cdd62cb470 0d144d1a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in ext4_buffered_write_iter
* Struck through repros no longer work on HEAD.