Messages in this thread | | | Date | Wed, 10 Jul 2019 01:07:06 -0700 | Subject | possible deadlock in shrink_dcache_parent | From | syzbot <> |
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Hello,
syzbot found the following crash on:
HEAD commit: 4608a726 Add linux-next specific files for 20190709 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=1126bd28600000 kernel config: https://syzkaller.appspot.com/x/.config?x=7a02e36d356a9a17 dashboard link: https://syzkaller.appspot.com/bug?extid=9b4ec36f6faf3ddb9102 compiler: gcc (GCC) 9.0.0 20181231 (experimental)
Unfortunately, I don't have any reproducer for this crash yet.
IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+9b4ec36f6faf3ddb9102@syzkaller.appspotmail.com
====================================================== WARNING: possible circular locking dependency detected 5.2.0-next-20190709 #34 Not tainted ------------------------------------------------------ syz-executor.1/9214 is trying to acquire lock: 00000000eb8ccf4b (rename_lock#2){+.+.}, at: shrink_dcache_parent+0xb7/0x430 fs/dcache.c:1544
but task is already holding lock: 000000002624bc34 (&(&dentry->d_lockref.lock)->rlock){+.+.}, at: spin_lock include/linux/spinlock.h:338 [inline] 000000002624bc34 (&(&dentry->d_lockref.lock)->rlock){+.+.}, at: shrink_dcache_parent+0x134/0x430 fs/dcache.c:1558
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&(&dentry->d_lockref.lock)->rlock){+.+.}: __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline] _raw_spin_lock+0x2f/0x40 kernel/locking/spinlock.c:151 spin_lock include/linux/spinlock.h:338 [inline] d_set_mounted+0x17e/0x2e0 fs/dcache.c:1434 get_mountpoint+0x166/0x3f0 fs/namespace.c:724 lock_mount+0xf1/0x2e0 fs/namespace.c:2131 do_add_mount+0x27/0x380 fs/namespace.c:2669 do_new_mount_fc fs/namespace.c:2730 [inline] do_new_mount fs/namespace.c:2785 [inline] do_mount+0x178f/0x1c30 fs/namespace.c:3103 ksys_mount+0xdb/0x150 fs/namespace.c:3312 devtmpfsd+0xbd/0x130 drivers/base/devtmpfs.c:397 kthread+0x361/0x430 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352
-> #0 (rename_lock#2){+.+.}: check_prev_add kernel/locking/lockdep.c:2405 [inline] check_prevs_add kernel/locking/lockdep.c:2507 [inline] validate_chain kernel/locking/lockdep.c:2897 [inline] __lock_acquire+0x25a9/0x4c30 kernel/locking/lockdep.c:3880 lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4413 seqcount_lockdep_reader_access include/linux/seqlock.h:81 [inline] read_seqcount_begin include/linux/seqlock.h:164 [inline] read_seqbegin include/linux/seqlock.h:433 [inline] read_seqbegin_or_lock include/linux/seqlock.h:529 [inline] d_walk+0xe8/0x950 fs/dcache.c:1277 shrink_dcache_parent+0xb7/0x430 fs/dcache.c:1544 vfs_rmdir fs/namei.c:3882 [inline] vfs_rmdir+0x26f/0x4f0 fs/namei.c:3857 do_rmdir+0x39e/0x420 fs/namei.c:3940 __do_sys_rmdir fs/namei.c:3958 [inline] __se_sys_rmdir fs/namei.c:3956 [inline] __x64_sys_rmdir+0x36/0x40 fs/namei.c:3956 do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1 ---- ---- lock(&(&dentry->d_lockref.lock)->rlock); lock(rename_lock#2); lock(&(&dentry->d_lockref.lock)->rlock); lock(rename_lock#2);
*** DEADLOCK ***
4 locks held by syz-executor.1/9214: #0: 000000000bbde6ea (sb_writers#3){.+.+}, at: sb_start_write include/linux/fs.h:1625 [inline] #0: 000000000bbde6ea (sb_writers#3){.+.+}, at: mnt_want_write+0x3f/0xc0 fs/namespace.c:354 #1: 00000000a93efd69 (&type->i_mutex_dir_key#3/1){+.+.}, at: inode_lock_nested include/linux/fs.h:813 [inline] #1: 00000000a93efd69 (&type->i_mutex_dir_key#3/1){+.+.}, at: do_rmdir+0x271/0x420 fs/namei.c:3928 #2: 000000000cbb3019 (&type->i_mutex_dir_key#3){++++}, at: inode_lock include/linux/fs.h:778 [inline] #2: 000000000cbb3019 (&type->i_mutex_dir_key#3){++++}, at: vfs_rmdir fs/namei.c:3868 [inline] #2: 000000000cbb3019 (&type->i_mutex_dir_key#3){++++}, at: vfs_rmdir+0xe5/0x4f0 fs/namei.c:3857 #3: 000000002624bc34 (&(&dentry->d_lockref.lock)->rlock){+.+.}, at: spin_lock include/linux/spinlock.h:338 [inline] #3: 000000002624bc34 (&(&dentry->d_lockref.lock)->rlock){+.+.}, at: shrink_dcache_parent+0x134/0x430 fs/dcache.c:1558
stack backtrace: CPU: 0 PID: 9214 Comm: syz-executor.1 Not tainted 5.2.0-next-20190709 #34 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x172/0x1f0 lib/dump_stack.c:113 print_circular_bug.cold+0x163/0x172 kernel/locking/lockdep.c:1617 check_noncircular+0x345/0x3e0 kernel/locking/lockdep.c:1741 check_prev_add kernel/locking/lockdep.c:2405 [inline] check_prevs_add kernel/locking/lockdep.c:2507 [inline] validate_chain kernel/locking/lockdep.c:2897 [inline] __lock_acquire+0x25a9/0x4c30 kernel/locking/lockdep.c:3880 lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4413 seqcount_lockdep_reader_access include/linux/seqlock.h:81 [inline] read_seqcount_begin include/linux/seqlock.h:164 [inline] read_seqbegin include/linux/seqlock.h:433 [inline] read_seqbegin_or_lock include/linux/seqlock.h:529 [inline] d_walk+0xe8/0x950 fs/dcache.c:1277 shrink_dcache_parent+0xb7/0x430 fs/dcache.c:1544 vfs_rmdir fs/namei.c:3882 [inline] vfs_rmdir+0x26f/0x4f0 fs/namei.c:3857 do_rmdir+0x39e/0x420 fs/namei.c:3940 __do_sys_rmdir fs/namei.c:3958 [inline] __se_sys_rmdir fs/namei.c:3956 [inline] __x64_sys_rmdir+0x36/0x40 fs/namei.c:3956 do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x459537 Code: 00 66 90 b8 57 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 7d ba fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 b8 54 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 5d ba fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ffea112f078 EFLAGS: 00000207 ORIG_RAX: 0000000000000054 RAX: ffffffffffffffda RBX: 0000000000000065 RCX: 0000000000459537 RDX: 0000000000000000 RSI: 0000000000714698 RDI: 00007ffea11301b0 RBP: 0000000000000555 R08: 0000000000000000 R09: 0000000000000001 R10: 000000000000000a R11: 0000000000000207 R12: 00007ffea11301b0 R13: 0000555555709940 R14: 0000000000000000 R15: 00007ffea11301b0 BUG: sleeping function called from invalid context at fs/dcache.c:1551 in_atomic(): 1, irqs_disabled(): 0, pid: 9214, name: syz-executor.1 INFO: lockdep is turned off. Preemption disabled at: [<ffffffff81bc3e14>] spin_lock include/linux/spinlock.h:338 [inline] [<ffffffff81bc3e14>] shrink_dcache_parent+0x134/0x430 fs/dcache.c:1558 CPU: 0 PID: 9214 Comm: syz-executor.1 Not tainted 5.2.0-next-20190709 #34 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x172/0x1f0 lib/dump_stack.c:113 ___might_sleep.cold+0x1be/0x1f7 kernel/sched/core.c:6603 shrink_dcache_parent+0xdc/0x430 fs/dcache.c:1551 vfs_rmdir fs/namei.c:3882 [inline] vfs_rmdir+0x26f/0x4f0 fs/namei.c:3857 do_rmdir+0x39e/0x420 fs/namei.c:3940 __do_sys_rmdir fs/namei.c:3958 [inline] __se_sys_rmdir fs/namei.c:3956 [inline] __x64_sys_rmdir+0x36/0x40 fs/namei.c:3956 do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x459537 Code: 00 66 90 b8 57 00 00 00 0f 05 48 3d 01 f0 ff ff 0f 83 7d ba fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 b8 54 00 00 00 0f 05 <48> 3d 01 f0 ff ff 0f 83 5d ba fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007ffea112f078 EFLAGS: 00000207 ORIG_RAX: 0000000000000054 RAX: ffffffffffffffda RBX: 0000000000000065 RCX: 0000000000459537 RDX: 0000000000000000 RSI: 0000000000714698 RDI: 00007ffea11301b0 RBP: 0000000000000555 R08: 0000000000000000 R09: 0000000000000001 R10: 000000000000000a R11: 0000000000000207 R12: 00007ffea11301b0 R13: 0000555555709940 R14: 0000000000000000 R15: 00007ffea11301b0 BUG: scheduling while atomic: syz-executor.1/9214/0x00000002 INFO: lockdep is turned off. Modules linked in: Preemption disabled at: [<ffffffff81bc3e14>] spin_lock include/linux/spinlock.h:338 [inline] [<ffffffff81bc3e14>] shrink_dcache_parent+0x134/0x430 fs/dcache.c:1558
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