Hello, syzbot found the following crash on: HEAD commit: 94f2630b Merge tag '5.6-rc-small-smb3-fix-for-stable' of g.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=11203a4ee00000 kernel config: https://syzkaller.appspot.com/x/.config?x=6dda7ccc1e75a63f dashboard link: https://syzkaller.appspot.com/bug?extid=86a925872c5fba672f8c compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81) 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+86a925872c5fba672f8c@xxxxxxxxxxxxxxxxxxxxxxxxx ====================================================== WARNING: possible circular locking dependency detected 5.5.0-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.4/2716 is trying to acquire lock: ffff888054af5d50 (&sig->cred_guard_mutex){+.+.}, at: do_io_accounting fs/proc/base.c:2864 [inline] ffff888054af5d50 (&sig->cred_guard_mutex){+.+.}, at: proc_tgid_io_accounting+0x16a/0x570 fs/proc/base.c:2913 but task is already holding lock: ffff8880926c4be0 (&p->lock){+.+.}, at: seq_read+0x6b/0xdb0 fs/seq_file.c:161 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (&p->lock){+.+.}: lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 __mutex_lock_common+0x16e/0x2f30 kernel/locking/mutex.c:956 __mutex_lock kernel/locking/mutex.c:1103 [inline] mutex_lock_nested+0x1b/0x30 kernel/locking/mutex.c:1118 seq_read+0x6b/0xdb0 fs/seq_file.c:161 proc_reg_read+0x1d5/0x2e0 fs/proc/inode.c:223 do_loop_readv_writev fs/read_write.c:714 [inline] do_iter_read+0x4a2/0x5b0 fs/read_write.c:935 vfs_readv+0xc2/0x120 fs/read_write.c:997 kernel_readv fs/splice.c:365 [inline] default_file_splice_read+0x579/0xa40 fs/splice.c:422 do_splice_to fs/splice.c:892 [inline] splice_direct_to_actor+0x3c9/0xb90 fs/splice.c:971 do_splice_direct+0x200/0x330 fs/splice.c:1080 do_sendfile+0x7e4/0xfd0 fs/read_write.c:1464 __do_sys_sendfile64 fs/read_write.c:1525 [inline] __se_sys_sendfile64 fs/read_write.c:1511 [inline] __x64_sys_sendfile64+0x176/0x1b0 fs/read_write.c:1511 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #3 (sb_writers#3){.+.+}: lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 percpu_down_read include/linux/percpu-rwsem.h:40 [inline] __sb_start_write+0x189/0x420 fs/super.c:1674 sb_start_write include/linux/fs.h:1650 [inline] mnt_want_write+0x4a/0xa0 fs/namespace.c:354 ovl_want_write+0x77/0x80 fs/overlayfs/util.c:21 ovl_create_object+0xaf/0x2d0 fs/overlayfs/dir.c:596 ovl_create+0x29/0x30 fs/overlayfs/dir.c:627 lookup_open fs/namei.c:3309 [inline] do_last fs/namei.c:3401 [inline] path_openat+0x230c/0x4380 fs/namei.c:3607 do_filp_open+0x192/0x3d0 fs/namei.c:3637 do_sys_openat2+0x42b/0x6f0 fs/open.c:1149 do_sys_open fs/open.c:1165 [inline] ksys_open include/linux/syscalls.h:1386 [inline] __do_sys_creat fs/open.c:1233 [inline] __se_sys_creat fs/open.c:1231 [inline] __x64_sys_creat+0xd5/0x100 fs/open.c:1231 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #2 (&ovl_i_mutex_dir_key[depth]){++++}: lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 down_read+0x39/0x50 kernel/locking/rwsem.c:1495 inode_lock_shared include/linux/fs.h:801 [inline] lookup_slow fs/namei.c:1773 [inline] lookup_one_len_unlocked+0xd2/0x1d0 fs/namei.c:2690 lookup_positive_unlocked+0x25/0xb0 fs/namei.c:2706 ovl_lookup_single+0x67/0x830 fs/overlayfs/namei.c:203 ovl_lookup_layer+0x3b1/0x470 fs/overlayfs/namei.c:287 ovl_lookup+0x843/0x1c60 fs/overlayfs/namei.c:902 lookup_open fs/namei.c:3288 [inline] do_last fs/namei.c:3401 [inline] path_openat+0x1b73/0x4380 fs/namei.c:3607 do_filp_open+0x192/0x3d0 fs/namei.c:3637 do_open_execat+0xff/0x620 fs/exec.c:860 __do_execve_file+0x758/0x1ca0 fs/exec.c:1765 do_execveat_common fs/exec.c:1871 [inline] do_execve fs/exec.c:1888 [inline] __do_sys_execve fs/exec.c:1964 [inline] __se_sys_execve fs/exec.c:1959 [inline] __x64_sys_execve+0x94/0xb0 fs/exec.c:1959 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (&ovl_i_mutex_dir_key[depth]#2){.+.+}: lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 down_read+0x39/0x50 kernel/locking/rwsem.c:1495 inode_lock_shared include/linux/fs.h:801 [inline] do_last fs/namei.c:3400 [inline] path_openat+0xbb7/0x4380 fs/namei.c:3607 do_filp_open+0x192/0x3d0 fs/namei.c:3637 do_open_execat+0xff/0x620 fs/exec.c:860 __do_execve_file+0x758/0x1ca0 fs/exec.c:1765 do_execveat_common fs/exec.c:1871 [inline] do_execve fs/exec.c:1888 [inline] __do_sys_execve fs/exec.c:1964 [inline] __se_sys_execve fs/exec.c:1959 [inline] __x64_sys_execve+0x94/0xb0 fs/exec.c:1959 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&sig->cred_guard_mutex){+.+.}: check_prev_add kernel/locking/lockdep.c:2475 [inline] check_prevs_add kernel/locking/lockdep.c:2580 [inline] validate_chain+0x1507/0x7be0 kernel/locking/lockdep.c:2970 __lock_acquire+0xc5a/0x1bc0 kernel/locking/lockdep.c:3954 lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 __mutex_lock_common+0x16e/0x2f30 kernel/locking/mutex.c:956 __mutex_lock kernel/locking/mutex.c:1103 [inline] mutex_lock_killable_nested+0x1b/0x30 kernel/locking/mutex.c:1133 do_io_accounting fs/proc/base.c:2864 [inline] proc_tgid_io_accounting+0x16a/0x570 fs/proc/base.c:2913 proc_single_show+0xe7/0x180 fs/proc/base.c:758 seq_read+0x4d8/0xdb0 fs/seq_file.c:229 do_loop_readv_writev fs/read_write.c:714 [inline] do_iter_read+0x4a2/0x5b0 fs/read_write.c:935 vfs_readv+0xc2/0x120 fs/read_write.c:997 kernel_readv fs/splice.c:365 [inline] default_file_splice_read+0x579/0xa40 fs/splice.c:422 do_splice_to fs/splice.c:892 [inline] splice_direct_to_actor+0x3c9/0xb90 fs/splice.c:971 do_splice_direct+0x200/0x330 fs/splice.c:1080 do_sendfile+0x7e4/0xfd0 fs/read_write.c:1464 __do_sys_sendfile64 fs/read_write.c:1525 [inline] __se_sys_sendfile64 fs/read_write.c:1511 [inline] __x64_sys_sendfile64+0x176/0x1b0 fs/read_write.c:1511 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: &sig->cred_guard_mutex --> sb_writers#3 --> &p->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&p->lock); lock(sb_writers#3); lock(&p->lock); lock(&sig->cred_guard_mutex); *** DEADLOCK *** 1 lock held by syz-executor.4/2716: #0: ffff8880926c4be0 (&p->lock){+.+.}, at: seq_read+0x6b/0xdb0 fs/seq_file.c:161 stack backtrace: CPU: 1 PID: 2716 Comm: syz-executor.4 Not tainted 5.5.0-syzkaller #0 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+0x1fb/0x318 lib/dump_stack.c:118 print_circular_bug+0xc3f/0xe70 kernel/locking/lockdep.c:1684 check_noncircular+0x206/0x3a0 kernel/locking/lockdep.c:1808 check_prev_add kernel/locking/lockdep.c:2475 [inline] check_prevs_add kernel/locking/lockdep.c:2580 [inline] validate_chain+0x1507/0x7be0 kernel/locking/lockdep.c:2970 __lock_acquire+0xc5a/0x1bc0 kernel/locking/lockdep.c:3954 lock_acquire+0x154/0x250 kernel/locking/lockdep.c:4484 __mutex_lock_common+0x16e/0x2f30 kernel/locking/mutex.c:956 __mutex_lock kernel/locking/mutex.c:1103 [inline] mutex_lock_killable_nested+0x1b/0x30 kernel/locking/mutex.c:1133 do_io_accounting fs/proc/base.c:2864 [inline] proc_tgid_io_accounting+0x16a/0x570 fs/proc/base.c:2913 proc_single_show+0xe7/0x180 fs/proc/base.c:758 seq_read+0x4d8/0xdb0 fs/seq_file.c:229 do_loop_readv_writev fs/read_write.c:714 [inline] do_iter_read+0x4a2/0x5b0 fs/read_write.c:935 vfs_readv+0xc2/0x120 fs/read_write.c:997 kernel_readv fs/splice.c:365 [inline] default_file_splice_read+0x579/0xa40 fs/splice.c:422 do_splice_to fs/splice.c:892 [inline] splice_direct_to_actor+0x3c9/0xb90 fs/splice.c:971 do_splice_direct+0x200/0x330 fs/splice.c:1080 do_sendfile+0x7e4/0xfd0 fs/read_write.c:1464 __do_sys_sendfile64 fs/read_write.c:1525 [inline] __se_sys_sendfile64 fs/read_write.c:1511 [inline] __x64_sys_sendfile64+0x176/0x1b0 fs/read_write.c:1511 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45b399 Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 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 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f0c198b1c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 00007f0c198b26d4 RCX: 000000000045b399 RDX: 0000000000000000 RSI: 0000000000000003 RDI: 0000000000000005 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 00000000010001ff R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000000008ca R14: 00000000004ca24d R15: 000000000075bf2c --- This bug is generated by a bot. 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