====================================================== [ INFO: possible circular locking dependency detected ] 4.9.128+ #93 Not tainted ------------------------------------------------------- syz-executor4/16868 is trying to acquire lock: (&p->lock){+.+.+.}, at: [] seq_read+0xdd/0x12d0 fs/seq_file.c:178 but task is already holding lock: (&pipe->mutex/1){+.+.+.}, at: [] pipe_lock_nested fs/pipe.c:66 [inline] (&pipe->mutex/1){+.+.+.}, at: [] pipe_lock+0x5e/0x70 fs/pipe.c:74 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756 __mutex_lock_common kernel/locking/mutex.c:521 [inline] mutex_lock_nested+0xc0/0x870 kernel/locking/mutex.c:621 __pipe_lock fs/pipe.c:87 [inline] fifo_open+0x15c/0x9e0 fs/pipe.c:921 do_dentry_open+0x3ef/0xc90 fs/open.c:766 vfs_open+0x11c/0x210 fs/open.c:879 do_last fs/namei.c:3410 [inline] path_openat+0x542/0x2790 fs/namei.c:3534 do_filp_open+0x197/0x270 fs/namei.c:3568 do_open_execat+0x10f/0x640 fs/exec.c:844 do_execveat_common.isra.15+0x687/0x1f80 fs/exec.c:1723 do_execve fs/exec.c:1829 [inline] SYSC_execve fs/exec.c:1910 [inline] SyS_execve+0x42/0x50 fs/exec.c:1905 do_syscall_64+0x19f/0x480 arch/x86/entry/common.c:282 entry_SYSCALL_64_after_swapgs+0x5d/0xdb lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756 __mutex_lock_common kernel/locking/mutex.c:521 [inline] mutex_lock_killable_nested+0xcc/0x960 kernel/locking/mutex.c:641 do_io_accounting+0x1fb/0x7e0 fs/proc/base.c:2676 proc_tgid_io_accounting+0x22/0x30 fs/proc/base.c:2725 proc_single_show+0xfd/0x170 fs/proc/base.c:771 seq_read+0x4b6/0x12d0 fs/seq_file.c:240 __vfs_read+0x115/0x560 fs/read_write.c:449 vfs_read+0x124/0x390 fs/read_write.c:472 SYSC_pread64 fs/read_write.c:626 [inline] SyS_pread64+0x145/0x170 fs/read_write.c:613 do_syscall_64+0x19f/0x480 arch/x86/entry/common.c:282 entry_SYSCALL_64_after_swapgs+0x5d/0xdb check_prev_add kernel/locking/lockdep.c:1828 [inline] check_prevs_add kernel/locking/lockdep.c:1938 [inline] validate_chain kernel/locking/lockdep.c:2265 [inline] __lock_acquire+0x3189/0x4a10 kernel/locking/lockdep.c:3345 lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756 __mutex_lock_common kernel/locking/mutex.c:521 [inline] mutex_lock_nested+0xc0/0x870 kernel/locking/mutex.c:621 seq_read+0xdd/0x12d0 fs/seq_file.c:178 proc_reg_read+0xfd/0x180 fs/proc/inode.c:203 do_loop_readv_writev.part.1+0xd5/0x280 fs/read_write.c:718 do_loop_readv_writev fs/read_write.c:707 [inline] do_readv_writev+0x56e/0x7b0 fs/read_write.c:873 vfs_readv+0x84/0xc0 fs/read_write.c:897 kernel_readv fs/splice.c:363 [inline] default_file_splice_read+0x44b/0x7e0 fs/splice.c:435 do_splice_to+0x10c/0x170 fs/splice.c:899 do_splice fs/splice.c:1192 [inline] SYSC_splice fs/splice.c:1416 [inline] SyS_splice+0x10d2/0x14d0 fs/splice.c:1399 do_syscall_64+0x19f/0x480 arch/x86/entry/common.c:282 entry_SYSCALL_64_after_swapgs+0x5d/0xdb other info that might help us debug this: Chain exists of: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&pipe->mutex/1); lock(&sig->cred_guard_mutex); lock(&pipe->mutex/1); lock(&p->lock); *** DEADLOCK *** 1 lock held by syz-executor4/16868: #0: (&pipe->mutex/1){+.+.+.}, at: [] pipe_lock_nested fs/pipe.c:66 [inline] #0: (&pipe->mutex/1){+.+.+.}, at: [] pipe_lock+0x5e/0x70 fs/pipe.c:74 stack backtrace: CPU: 1 PID: 16868 Comm: syz-executor4 Not tainted 4.9.128+ #93 ffff8801d2c57278 ffffffff81af2469 ffffffff83aa1330 ffffffff83aa85f0 ffffffff83aa2c80 ffff8801d68467d0 ffff8801d6845f00 ffff8801d2c572c0 ffffffff813e79ed 0000000000000001 00000000d68467b0 0000000000000001 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] print_circular_bug.cold.36+0x2f7/0x432 kernel/locking/lockdep.c:1202 [] check_prev_add kernel/locking/lockdep.c:1828 [inline] [] check_prevs_add kernel/locking/lockdep.c:1938 [inline] [] validate_chain kernel/locking/lockdep.c:2265 [inline] [] __lock_acquire+0x3189/0x4a10 kernel/locking/lockdep.c:3345 [] lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756 [] __mutex_lock_common kernel/locking/mutex.c:521 [inline] [] mutex_lock_nested+0xc0/0x870 kernel/locking/mutex.c:621 [] seq_read+0xdd/0x12d0 fs/seq_file.c:178 [] proc_reg_read+0xfd/0x180 fs/proc/inode.c:203 [] do_loop_readv_writev.part.1+0xd5/0x280 fs/read_write.c:718 [] do_loop_readv_writev fs/read_write.c:707 [inline] [] do_readv_writev+0x56e/0x7b0 fs/read_write.c:873 [] vfs_readv+0x84/0xc0 fs/read_write.c:897 [] kernel_readv fs/splice.c:363 [inline] [] default_file_splice_read+0x44b/0x7e0 fs/splice.c:435 [] do_splice_to+0x10c/0x170 fs/splice.c:899 [] do_splice fs/splice.c:1192 [inline] [] SYSC_splice fs/splice.c:1416 [inline] [] SyS_splice+0x10d2/0x14d0 fs/splice.c:1399 [] do_syscall_64+0x19f/0x480 arch/x86/entry/common.c:282 [] entry_SYSCALL_64_after_swapgs+0x5d/0xdb