On Mon, Apr 10, 2023 at 11:53:46PM -0700, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 0d3eb744aed4 Merge tag 'urgent-rcu.2023.04.07a' of git://g.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=11798e4bc80000 > kernel config: https://syzkaller.appspot.com/x/.config?x=c21559e740385326 > dashboard link: https://syzkaller.appspot.com/bug?extid=cdcd444e4d3a256ada13 > 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. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/a02928003efa/disk-0d3eb744.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/7839447005a4/vmlinux-0d3eb744.xz > kernel image: https://storage.googleapis.com/syzbot-assets/d26ab3184148/bzImage-0d3eb744.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+cdcd444e4d3a256ada13@xxxxxxxxxxxxxxxxxxxxxxxxx > > ====================================================== > WARNING: possible circular locking dependency detected > 6.3.0-rc6-syzkaller-00016-g0d3eb744aed4 #0 Not tainted > ------------------------------------------------------ > syz-executor.3/11858 is trying to acquire lock: > ffff88802a3bc0e0 (&type->s_umount_key#31){++++}-{3:3}, at: __do_sys_quotactl_fd+0x174/0x3f0 fs/quota/quota.c:997 > > but task is already holding lock: > ffff88802a3bc460 (sb_writers#4){.+.+}-{0:0}, at: __do_sys_quotactl_fd+0xd3/0x3f0 fs/quota/quota.c:990 > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #1 (sb_writers#4){.+.+}-{0:0}: > percpu_down_read include/linux/percpu-rwsem.h:51 [inline] > __sb_start_write include/linux/fs.h:1477 [inline] > sb_start_write include/linux/fs.h:1552 [inline] > write_mmp_block+0xc4/0x820 fs/ext4/mmp.c:50 > ext4_multi_mount_protect+0x50d/0xac0 fs/ext4/mmp.c:343 > __ext4_remount fs/ext4/super.c:6543 [inline] > ext4_reconfigure+0x242b/0x2b60 fs/ext4/super.c:6642 > reconfigure_super+0x40c/0xa30 fs/super.c:956 > vfs_fsconfig_locked fs/fsopen.c:254 [inline] > __do_sys_fsconfig+0xa3a/0xc20 fs/fsopen.c:439 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > -> #0 (&type->s_umount_key#31){++++}-{3:3}: > check_prev_add kernel/locking/lockdep.c:3098 [inline] > check_prevs_add kernel/locking/lockdep.c:3217 [inline] > validate_chain kernel/locking/lockdep.c:3832 [inline] > __lock_acquire+0x2ec7/0x5d40 kernel/locking/lockdep.c:5056 > lock_acquire kernel/locking/lockdep.c:5669 [inline] > lock_acquire+0x1af/0x520 kernel/locking/lockdep.c:5634 > down_write+0x92/0x200 kernel/locking/rwsem.c:1573 > __do_sys_quotactl_fd+0x174/0x3f0 fs/quota/quota.c:997 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x39/0xb0 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(sb_writers#4); > lock(&type->s_umount_key#31); > lock(sb_writers#4); > lock(&type->s_umount_key#31); > > *** DEADLOCK *** Hmkay, I understand how this happens, I think: fsconfig(FSCONFIG_CMD_RECONFIGURE) quotactl_fd(Q_QUOTAON/Q_QUOTAOFF/Q_XQUOTAON/Q_XQUOTAOFF) -> mnt_want_write(f.file->f_path.mnt); -> down_write(&sb->s_umount); -> __sb_start_write(sb, SB_FREEZE_WRITE) -> reconfigure_super(fc); -> ext4_multi_mount_protect() -> __sb_start_write(sb, SB_FREEZE_WRITE) -> down_write(&sb->s_umount); -> up_write(&sb->s_umount); I have to step away from the computer now for a bit but naively it seem that the locking order for quotactl_fd() should be the other way around. But while I'm here, why does quotactl_fd() take mnt_want_write() but quotactl() doesn't? It seems that if one needs to take it both need to take it. > > 1 lock held by syz-executor.3/11858: > #0: ffff88802a3bc460 (sb_writers#4){.+.+}-{0:0}, at: __do_sys_quotactl_fd+0xd3/0x3f0 fs/quota/quota.c:990 > > stack backtrace: > CPU: 0 PID: 11858 Comm: syz-executor.3 Not tainted 6.3.0-rc6-syzkaller-00016-g0d3eb744aed4 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023 > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0xd9/0x150 lib/dump_stack.c:106 > check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2178 > check_prev_add kernel/locking/lockdep.c:3098 [inline] > check_prevs_add kernel/locking/lockdep.c:3217 [inline] > validate_chain kernel/locking/lockdep.c:3832 [inline] > __lock_acquire+0x2ec7/0x5d40 kernel/locking/lockdep.c:5056 > lock_acquire kernel/locking/lockdep.c:5669 [inline] > lock_acquire+0x1af/0x520 kernel/locking/lockdep.c:5634 > down_write+0x92/0x200 kernel/locking/rwsem.c:1573 > __do_sys_quotactl_fd+0x174/0x3f0 fs/quota/quota.c:997 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > RIP: 0033:0x7f81d2e8c169 > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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:00007f81d3b29168 EFLAGS: 00000246 ORIG_RAX: 00000000000001bb > RAX: ffffffffffffffda RBX: 00007f81d2fabf80 RCX: 00007f81d2e8c169 > RDX: 0000000000000000 RSI: ffffffff80000300 RDI: 0000000000000003 > RBP: 00007f81d2ee7ca1 R08: 0000000000000000 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 > R13: 00007fffeeb18d7f R14: 00007f81d3b29300 R15: 0000000000022000 > </TASK> > > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. On Mon, Apr 10, 2023 at 11:53:46PM -0700, syzbot wrote: > Hello, > > syzbot found the following issue on: > > HEAD commit: 76f598ba7d8e Merge tag 'for-linus' of git://git.kernel.org.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=13965b21c80000 > kernel config: https://syzkaller.appspot.com/x/.config?x=5666fa6aca264e42 > dashboard link: https://syzkaller.appspot.com/bug?extid=aacb82fca60873422114 > compiler: Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2 > > Unfortunately, I don't have any reproducer for this issue yet. > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/1f01c9748997/disk-76f598ba.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/b3afb4fc86b9/vmlinux-76f598ba.xz > kernel image: https://storage.googleapis.com/syzbot-assets/8908040d7a31/bzImage-76f598ba.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+aacb82fca60873422114@xxxxxxxxxxxxxxxxxxxxxxxxx > > ====================================================== > WARNING: possible circular locking dependency detected > 6.3.0-rc5-syzkaller-00022-g76f598ba7d8e #0 Not tainted > ------------------------------------------------------ > syz-executor.0/17940 is trying to acquire lock: > ffff88802a89e0e0 (&type->s_umount_key#31){++++}-{3:3}, at: __do_sys_quotactl_fd fs/quota/quota.c:999 [inline] > ffff88802a89e0e0 (&type->s_umount_key#31){++++}-{3:3}, at: __se_sys_quotactl_fd+0x2fb/0x440 fs/quota/quota.c:972 > > but task is already holding lock: > ffff88802a89e460 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:394 > > which lock already depends on the new lock. > > > the existing dependency chain (in reverse order) is: > > -> #1 (sb_writers#4){.+.+}-{0:0}: > lock_acquire+0x1e1/0x520 kernel/locking/lockdep.c:5669 > percpu_down_read include/linux/percpu-rwsem.h:51 [inline] > __sb_start_write include/linux/fs.h:1477 [inline] > sb_start_write include/linux/fs.h:1552 [inline] > write_mmp_block+0xe5/0x930 fs/ext4/mmp.c:50 > ext4_multi_mount_protect+0x364/0x990 fs/ext4/mmp.c:343 > __ext4_remount fs/ext4/super.c:6543 [inline] > ext4_reconfigure+0x29a8/0x3280 fs/ext4/super.c:6642 > reconfigure_super+0x3c9/0x7c0 fs/super.c:956 > vfs_fsconfig_locked fs/fsopen.c:254 [inline] > __do_sys_fsconfig fs/fsopen.c:439 [inline] > __se_sys_fsconfig+0xa29/0xf70 fs/fsopen.c:314 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > -> #0 (&type->s_umount_key#31){++++}-{3:3}: > check_prev_add kernel/locking/lockdep.c:3098 [inline] > check_prevs_add kernel/locking/lockdep.c:3217 [inline] > validate_chain+0x166b/0x58e0 kernel/locking/lockdep.c:3832 > __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056 > lock_acquire+0x1e1/0x520 kernel/locking/lockdep.c:5669 > down_read+0x3d/0x50 kernel/locking/rwsem.c:1520 > __do_sys_quotactl_fd fs/quota/quota.c:999 [inline] > __se_sys_quotactl_fd+0x2fb/0x440 fs/quota/quota.c:972 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x41/0xc0 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(sb_writers#4); > lock(&type->s_umount_key#31); > lock(sb_writers#4); > lock(&type->s_umount_key#31); > > *** DEADLOCK *** > > 1 lock held by syz-executor.0/17940: > #0: ffff88802a89e460 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:394 > > stack backtrace: > CPU: 0 PID: 17940 Comm: syz-executor.0 Not tainted 6.3.0-rc5-syzkaller-00022-g76f598ba7d8e #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023 > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0x1e7/0x2d0 lib/dump_stack.c:106 > check_noncircular+0x2fe/0x3b0 kernel/locking/lockdep.c:2178 > check_prev_add kernel/locking/lockdep.c:3098 [inline] > check_prevs_add kernel/locking/lockdep.c:3217 [inline] > validate_chain+0x166b/0x58e0 kernel/locking/lockdep.c:3832 > __lock_acquire+0x125b/0x1f80 kernel/locking/lockdep.c:5056 > lock_acquire+0x1e1/0x520 kernel/locking/lockdep.c:5669 > down_read+0x3d/0x50 kernel/locking/rwsem.c:1520 > __do_sys_quotactl_fd fs/quota/quota.c:999 [inline] > __se_sys_quotactl_fd+0x2fb/0x440 fs/quota/quota.c:972 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > RIP: 0033:0x7f3c2aa8c169 > Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 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:00007f3c2b826168 EFLAGS: 00000246 ORIG_RAX: 00000000000001bb > RAX: ffffffffffffffda RBX: 00007f3c2ababf80 RCX: 00007f3c2aa8c169 > RDX: ffffffffffffffff RSI: ffffffff80000601 RDI: 0000000000000003 > RBP: 00007f3c2aae7ca1 R08: 0000000000000000 R09: 0000000000000000 > R10: 00000000200024c0 R11: 0000000000000246 R12: 0000000000000000 > R13: 00007ffd71f38adf R14: 00007f3c2b826300 R15: 0000000000022000 > </TASK> > > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
