Hello, syzbot found the following issue on: HEAD commit: b51594df Merge tag 'docs-5.9-3' of git://git.lwn.net/linux git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=12bcc1c1900000 kernel config: https://syzkaller.appspot.com/x/.config?x=e1c560d0f4e121c9 dashboard link: https://syzkaller.appspot.com/bug?extid=a196bb0e96837b9ae756 compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81) 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+a196bb0e96837b9ae756@xxxxxxxxxxxxxxxxxxxxxxxxx ====================================================== WARNING: possible circular locking dependency detected 5.9.0-rc3-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.0/609 is trying to acquire lock: ffff88804da52c68 (&pipe->mutex/1){+.+.}-{3:3}, at: iter_file_splice_write+0x1b4/0xdf0 fs/splice.c:699 but task is already holding lock: ffff888098062450 (sb_writers#4){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2783 [inline] ffff888098062450 (sb_writers#4){.+.+}-{0:0}, at: do_splice+0xd4b/0x1a50 fs/splice.c:1143 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #4 (sb_writers#4){.+.+}-{0:0}: lock_acquire+0x140/0x6f0 kernel/locking/lockdep.c:5006 percpu_down_read include/linux/percpu-rwsem.h:51 [inline] __sb_start_write+0x14b/0x410 fs/super.c:1672 sb_start_write include/linux/fs.h:1643 [inline] mnt_want_write+0x45/0x90 fs/namespace.c:354 ovl_create_object+0xb1/0x2b0 fs/overlayfs/dir.c:625 lookup_open fs/namei.c:3103 [inline] open_last_lookups fs/namei.c:3177 [inline] path_openat+0x17e1/0x3840 fs/namei.c:3365 do_filp_open+0x191/0x3a0 fs/namei.c:3395 do_sys_openat2+0x463/0x830 fs/open.c:1168 do_sys_open fs/open.c:1184 [inline] __do_sys_open fs/open.c:1192 [inline] __se_sys_open fs/open.c:1188 [inline] __x64_sys_open+0x1af/0x1e0 fs/open.c:1188 do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #3 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}: lock_acquire+0x140/0x6f0 kernel/locking/lockdep.c:5006 down_read+0x36/0x50 kernel/locking/rwsem.c:1492 inode_lock_shared include/linux/fs.h:789 [inline] lookup_slow fs/namei.c:1560 [inline] walk_component+0x435/0x680 fs/namei.c:1860 lookup_last fs/namei.c:2309 [inline] path_lookupat+0x19d/0x960 fs/namei.c:2333 filename_lookup+0x1ab/0x5d0 fs/namei.c:2366 create_local_trace_uprobe+0x3f/0x5f0 kernel/trace/trace_uprobe.c:1574 perf_uprobe_init+0xfe/0x1a0 kernel/trace/trace_event_perf.c:323 perf_uprobe_event_init+0xfe/0x180 kernel/events/core.c:9580 perf_try_init_event+0x13e/0x3a0 kernel/events/core.c:10899 perf_init_event kernel/events/core.c:10951 [inline] perf_event_alloc+0xda1/0x28f0 kernel/events/core.c:11229 __do_sys_perf_event_open kernel/events/core.c:11724 [inline] __se_sys_perf_event_open+0x6e7/0x3f60 kernel/events/core.c:11598 do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #2 (&sig->exec_update_mutex){+.+.}-{3:3}: lock_acquire+0x140/0x6f0 kernel/locking/lockdep.c:5006 __mutex_lock_common+0x189/0x2fc0 kernel/locking/mutex.c:956 __mutex_lock kernel/locking/mutex.c:1103 [inline] mutex_lock_killable_nested+0x1a/0x20 kernel/locking/mutex.c:1133 exec_mmap fs/exec.c:1113 [inline] begin_new_exec+0x66c/0x15c0 fs/exec.c:1392 load_elf_binary+0x60f/0x48a0 fs/binfmt_elf.c:974 search_binary_handler fs/exec.c:1819 [inline] exec_binprm fs/exec.c:1860 [inline] bprm_execve+0x919/0x1500 fs/exec.c:1931 kernel_execve+0x871/0x970 fs/exec.c:2080 try_to_run_init_process init/main.c:1344 [inline] kernel_init+0xc4/0x290 init/main.c:1453 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 -> #1 (&sig->cred_guard_mutex){+.+.}-{3:3}: lock_acquire+0x140/0x6f0 kernel/locking/lockdep.c:5006 __mutex_lock_common+0x189/0x2fc0 kernel/locking/mutex.c:956 __mutex_lock kernel/locking/mutex.c:1103 [inline] mutex_lock_interruptible_nested+0x1a/0x20 kernel/locking/mutex.c:1140 proc_pid_attr_write+0x3b4/0x4a0 fs/proc/base.c:2734 __kernel_write+0x1ac/0xac0 fs/read_write.c:528 write_pipe_buf+0xf9/0x150 fs/splice.c:799 splice_from_pipe_feed fs/splice.c:502 [inline] __splice_from_pipe+0x351/0x8b0 fs/splice.c:626 splice_from_pipe fs/splice.c:661 [inline] default_file_splice_write fs/splice.c:811 [inline] do_splice_from fs/splice.c:847 [inline] do_splice+0xf1b/0x1a50 fs/splice.c:1144 __do_sys_splice fs/splice.c:1419 [inline] __se_sys_splice fs/splice.c:1401 [inline] __x64_sys_splice+0x14f/0x1f0 fs/splice.c:1401 do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #0 (&pipe->mutex/1){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:2496 [inline] check_prevs_add kernel/locking/lockdep.c:2601 [inline] validate_chain+0x1b0c/0x88a0 kernel/locking/lockdep.c:3218 __lock_acquire+0x110b/0x2ae0 kernel/locking/lockdep.c:4426 lock_acquire+0x140/0x6f0 kernel/locking/lockdep.c:5006 __mutex_lock_common+0x189/0x2fc0 kernel/locking/mutex.c:956 __mutex_lock kernel/locking/mutex.c:1103 [inline] mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1118 iter_file_splice_write+0x1b4/0xdf0 fs/splice.c:699 do_splice_from fs/splice.c:846 [inline] do_splice+0xdd1/0x1a50 fs/splice.c:1144 __do_sys_splice fs/splice.c:1419 [inline] __se_sys_splice fs/splice.c:1401 [inline] __x64_sys_splice+0x14f/0x1f0 fs/splice.c:1401 do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 other info that might help us debug this: Chain exists of: &pipe->mutex/1 --> &ovl_i_mutex_dir_key[depth] --> sb_writers#4 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sb_writers#4); lock(&ovl_i_mutex_dir_key[depth]); lock(sb_writers#4); lock(&pipe->mutex/1); *** DEADLOCK *** 1 lock held by syz-executor.0/609: #0: ffff888098062450 (sb_writers#4){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2783 [inline] #0: ffff888098062450 (sb_writers#4){.+.+}-{0:0}, at: do_splice+0xd4b/0x1a50 fs/splice.c:1143 stack backtrace: CPU: 1 PID: 609 Comm: syz-executor.0 Not tainted 5.9.0-rc3-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+0x1d6/0x29e lib/dump_stack.c:118 print_circular_bug+0xc72/0xea0 kernel/locking/lockdep.c:1703 check_noncircular+0x1fb/0x3a0 kernel/locking/lockdep.c:1827 check_prev_add kernel/locking/lockdep.c:2496 [inline] check_prevs_add kernel/locking/lockdep.c:2601 [inline] validate_chain+0x1b0c/0x88a0 kernel/locking/lockdep.c:3218 __lock_acquire+0x110b/0x2ae0 kernel/locking/lockdep.c:4426 lock_acquire+0x140/0x6f0 kernel/locking/lockdep.c:5006 __mutex_lock_common+0x189/0x2fc0 kernel/locking/mutex.c:956 __mutex_lock kernel/locking/mutex.c:1103 [inline] mutex_lock_nested+0x1a/0x20 kernel/locking/mutex.c:1118 iter_file_splice_write+0x1b4/0xdf0 fs/splice.c:699 do_splice_from fs/splice.c:846 [inline] do_splice+0xdd1/0x1a50 fs/splice.c:1144 __do_sys_splice fs/splice.c:1419 [inline] __se_sys_splice fs/splice.c:1401 [inline] __x64_sys_splice+0x14f/0x1f0 fs/splice.c:1401 do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x45d5b9 Code: 5d b4 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 2b b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fc20cea2c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000113 RAX: ffffffffffffffda RBX: 0000000000033980 RCX: 000000000045d5b9 RDX: 0000000000000005 RSI: 0000000000000000 RDI: 0000000000000004 RBP: 000000000118d038 R08: 00000000ffffffff R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cfec R13: 00007ffecc00982f R14: 00007fc20cea39c0 R15: 000000000118cfec --- This report is generated by a bot. 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