On Fri, Aug 12, 2022 at 10:46:16AM +0800, 'Jason Yan' via syzkaller-bugs wrote: > The inode_lock(inode) in vfs_fileattr_set() is a regular file inode and > inode_lock_shared(inode) in ext4_bmap() is a journal inode. > > So this might be a false positive deadlock warning. > > Thanks, > Jason > > On 2022/8/8 15:33, syzbot wrote: > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: ca688bff68bc Add linux-next specific files for 20220808 > > git tree: linux-next > > console output: https://syzkaller.appspot.com/x/log.txt?x=177eb001080000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=4c20e006003cdecb > > dashboard link: https://syzkaller.appspot.com/bug?extid=9543479984ae9e576000 > > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+9543479984ae9e576000@xxxxxxxxxxxxxxxxxxxxxxxxx > > > > ====================================================== > > WARNING: possible circular locking dependency detected > > 5.19.0-next-20220808-syzkaller #0 Not tainted > > ------------------------------------------------------ > > syz-executor.3/15950 is trying to acquire lock: > > ffff88801b348400 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: inode_lock_shared include/linux/fs.h:771 [inline] > > ffff88801b348400 (&sb->s_type->i_mutex_key#8){++++}-{3:3}, at: ext4_bmap+0x4e/0x460 fs/ext4/inode.c:3157 > > > > but task is already holding lock: > > ffff88814bede3f8 (&journal->j_checkpoint_mutex){+.+.}-{3:3}, at: jbd2_journal_flush+0x487/0xc00 fs/jbd2/journal.c:2472 > > > > which lock already depends on the new lock. > > > > > > the existing dependency chain (in reverse order) is: > > > > -> #1 (&journal->j_checkpoint_mutex){+.+.}-{3:3}: > > __mutex_lock_common kernel/locking/mutex.c:603 [inline] > > mutex_lock_io_nested+0x13f/0x1190 kernel/locking/mutex.c:833 > > __jbd2_log_wait_for_space+0x234/0x460 fs/jbd2/checkpoint.c:110 > > add_transaction_credits+0xa2d/0xb70 fs/jbd2/transaction.c:298 > > start_this_handle+0x3ae/0x14a0 fs/jbd2/transaction.c:422 > > jbd2__journal_start+0x38c/0x910 fs/jbd2/transaction.c:520 > > __ext4_journal_start_sb+0x3a3/0x490 fs/ext4/ext4_jbd2.c:105 > > __ext4_journal_start fs/ext4/ext4_jbd2.h:326 [inline] > > ext4_dirty_inode+0x9d/0x110 fs/ext4/inode.c:5963 > > __mark_inode_dirty+0x48b/0x1040 fs/fs-writeback.c:2381 > > mark_inode_dirty include/linux/fs.h:2467 [inline] > > generic_write_end+0x350/0x440 fs/buffer.c:2199 > > ext4_da_write_end+0x16e/0x9a0 fs/ext4/inode.c:3089 > > generic_perform_write+0x306/0x560 mm/filemap.c:3749 > > ext4_buffered_write_iter+0x15b/0x460 fs/ext4/file.c:270 > > ext4_file_write_iter+0x44a/0x1660 fs/ext4/file.c:679 > > call_write_iter include/linux/fs.h:2192 [inline] > > do_iter_readv_writev+0x20b/0x3b0 fs/read_write.c:729 > > do_iter_write+0x182/0x700 fs/read_write.c:855 > > vfs_iter_write+0x70/0xa0 fs/read_write.c:896 > > iter_file_splice_write+0x741/0xc90 fs/splice.c:686 > > do_splice_from fs/splice.c:764 [inline] > > direct_splice_actor+0x110/0x180 fs/splice.c:931 > > splice_direct_to_actor+0x331/0x8a0 fs/splice.c:886 > > do_splice_direct+0x1a7/0x270 fs/splice.c:974 > > do_sendfile+0xb19/0x1270 fs/read_write.c:1249 > > __do_sys_sendfile64 fs/read_write.c:1311 [inline] > > __se_sys_sendfile64 fs/read_write.c:1303 [inline] > > __x64_sys_sendfile64+0x149/0x210 fs/read_write.c:1303 > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > > > -> #0 (&sb->s_type->i_mutex_key#8){++++}-{3:3}: > > check_prev_add kernel/locking/lockdep.c:3095 [inline] > > check_prevs_add kernel/locking/lockdep.c:3214 [inline] > > validate_chain kernel/locking/lockdep.c:3829 [inline] > > __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5053 > > lock_acquire kernel/locking/lockdep.c:5666 [inline] > > lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631 > > down_read+0x98/0x450 kernel/locking/rwsem.c:1499 > > inode_lock_shared include/linux/fs.h:771 [inline] > > ext4_bmap+0x4e/0x460 fs/ext4/inode.c:3157 > > bmap+0xaa/0x120 fs/inode.c:1799 > > jbd2_journal_bmap+0xa8/0x180 fs/jbd2/journal.c:971 > > __jbd2_journal_erase fs/jbd2/journal.c:1784 [inline] > > jbd2_journal_flush+0x84f/0xc00 fs/jbd2/journal.c:2490 > > ext4_ioctl_checkpoint fs/ext4/ioctl.c:1082 [inline] > > __ext4_ioctl+0x28fd/0x4ab0 fs/ext4/ioctl.c:1586 > > vfs_ioctl fs/ioctl.c:51 [inline] > > __do_sys_ioctl fs/ioctl.c:870 [inline] > > __se_sys_ioctl fs/ioctl.c:856 [inline] > > __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856 > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > > > other info that might help us debug this: > > > > Possible unsafe locking scenario: > > > > CPU0 CPU1 > > ---- ---- > > lock(&journal->j_checkpoint_mutex); > > lock(&sb->s_type->i_mutex_key#8); > > lock(&journal->j_checkpoint_mutex); > > lock(&sb->s_type->i_mutex_key#8); > > > > *** DEADLOCK *** > > > > 2 locks held by syz-executor.3/15950: > > #0: ffff88814bede170 (&journal->j_barrier){+.+.}-{3:3}, at: jbd2_journal_lock_updates+0x15e/0x310 fs/jbd2/transaction.c:904 > > #1: ffff88814bede3f8 (&journal->j_checkpoint_mutex){+.+.}-{3:3}, at: jbd2_journal_flush+0x487/0xc00 fs/jbd2/journal.c:2472 > > > > stack backtrace: > > CPU: 1 PID: 15950 Comm: syz-executor.3 Not tainted 5.19.0-next-20220808-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022 > > Call Trace: > > <TASK> > > __dump_stack lib/dump_stack.c:88 [inline] > > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 > > check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2175 > > check_prev_add kernel/locking/lockdep.c:3095 [inline] > > check_prevs_add kernel/locking/lockdep.c:3214 [inline] > > validate_chain kernel/locking/lockdep.c:3829 [inline] > > __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5053 > > lock_acquire kernel/locking/lockdep.c:5666 [inline] > > lock_acquire+0x1ab/0x570 kernel/locking/lockdep.c:5631 > > down_read+0x98/0x450 kernel/locking/rwsem.c:1499 > > inode_lock_shared include/linux/fs.h:771 [inline] > > ext4_bmap+0x4e/0x460 fs/ext4/inode.c:3157 > > bmap+0xaa/0x120 fs/inode.c:1799 > > jbd2_journal_bmap+0xa8/0x180 fs/jbd2/journal.c:971 > > __jbd2_journal_erase fs/jbd2/journal.c:1784 [inline] > > jbd2_journal_flush+0x84f/0xc00 fs/jbd2/journal.c:2490 > > ext4_ioctl_checkpoint fs/ext4/ioctl.c:1082 [inline] > > __ext4_ioctl+0x28fd/0x4ab0 fs/ext4/ioctl.c:1586 > > vfs_ioctl fs/ioctl.c:51 [inline] > > __do_sys_ioctl fs/ioctl.c:870 [inline] > > __se_sys_ioctl fs/ioctl.c:856 [inline] > > __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856 > > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > > do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 > > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > RIP: 0033:0x7feb4e689279 > > 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 b8 ff ff ff f7 d8 64 89 01 48 > > RSP: 002b:00007feb4f798168 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 > > RAX: ffffffffffffffda RBX: 00007feb4e79bf80 RCX: 00007feb4e689279 > > RDX: 0000000020000000 RSI: 000000004004662b RDI: 0000000000000005 > > RBP: 00007feb4e6e3189 R08: 0000000000000000 R09: 0000000000000000 > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > > R13: 00007ffc38bb538f R14: 00007feb4f798300 R15: 0000000000022000 > > </TASK> > > > > I got this report while running syzkaller too. It's very annoying because anyone running syzkaller will probably get this if the filesystem is ext4. ext4_bmap() didn't use to take the inode lock. It started in this very recent commit: commit 51ae846cff568c8c29921b1b28eb2dfbcd4ac12d Author: Ye Bin <yebin10@xxxxxxxxxx> Date: Fri Jun 17 09:39:35 2022 +0800 ext4: fix warning in ext4_iomap_begin as race between bmap and write Ye, any thoughts on what to do about this? - Eric
