====================================================== WARNING: possible circular locking dependency detected 5.8.0-rc7-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.0/4341 is trying to acquire lock: ffff888096c70540 (&p->lock){+.+.}-{3:3}, at: seq_read+0x60/0xce0 fs/seq_file.c:155 but task is already holding lock: ffff8880a8d74450 (sb_writers#4){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2918 [inline] ffff8880a8d74450 (sb_writers#4){.+.+}-{0:0}, at: do_sendfile+0x7dd/0xfe0 fs/read_write.c:1539 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (sb_writers#4){.+.+}-{0:0}: lock_acquire+0x160/0x720 kernel/locking/lockdep.c:4959 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:1665 [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:3095 [inline] open_last_lookups fs/namei.c:3169 [inline] path_openat+0x17db/0x37f0 fs/namei.c:3357 do_filp_open+0x191/0x3a0 fs/namei.c:3387 do_sys_openat2+0x463/0x770 fs/open.c:1179 do_sys_open fs/open.c:1195 [inline] ksys_open include/linux/syscalls.h:1388 [inline] __do_sys_creat fs/open.c:1263 [inline] __se_sys_creat fs/open.c:1261 [inline] __x64_sys_creat+0xd3/0x100 fs/open.c:1261 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #2 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}: lock_acquire+0x160/0x720 kernel/locking/lockdep.c:4959 down_read+0x36/0x50 kernel/locking/rwsem.c:1492 inode_lock_shared include/linux/fs.h:810 [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:1575 perf_uprobe_init+0xfe/0x1a0 kernel/trace/trace_event_perf.c:323 perf_uprobe_event_init+0xfe/0x180 kernel/events/core.c:9481 perf_try_init_event+0x13e/0x3a0 kernel/events/core.c:10782 perf_init_event kernel/events/core.c:10834 [inline] perf_event_alloc+0xdb1/0x2870 kernel/events/core.c:11110 __do_sys_perf_event_open kernel/events/core.c:11605 [inline] __se_sys_perf_event_open+0x6e2/0x3fa0 kernel/events/core.c:11479 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #1 (&sig->exec_update_mutex){+.+.}-{3:3}: lock_acquire+0x160/0x720 kernel/locking/lockdep.c:4959 __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 do_io_accounting fs/proc/base.c:2919 [inline] proc_tid_io_accounting+0x156/0x210 fs/proc/base.c:2962 proc_single_show+0xf6/0x180 fs/proc/base.c:766 seq_read+0x41a/0xce0 fs/seq_file.c:208 do_loop_readv_writev fs/read_write.c:734 [inline] do_iter_read+0x44b/0x550 fs/read_write.c:955 vfs_readv+0xc2/0x120 fs/read_write.c:1073 kernel_readv fs/splice.c:355 [inline] default_file_splice_read+0x579/0xa40 fs/splice.c:412 do_splice_to fs/splice.c:871 [inline] splice_direct_to_actor+0x3de/0xb60 fs/splice.c:950 do_splice_direct+0x201/0x340 fs/splice.c:1059 do_sendfile+0x809/0xfe0 fs/read_write.c:1540 __do_sys_sendfile64 fs/read_write.c:1601 [inline] __se_sys_sendfile64 fs/read_write.c:1587 [inline] __x64_sys_sendfile64+0x164/0x1a0 fs/read_write.c:1587 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384 entry_SYSCALL_64_after_hwframe+0x44/0xa9 -> #0 (&p->lock){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:2496 [inline] check_prevs_add kernel/locking/lockdep.c:2601 [inline] validate_chain+0x1b0c/0x8920 kernel/locking/lockdep.c:3218 __lock_acquire+0x116c/0x2c30 kernel/locking/lockdep.c:4380 lock_acquire+0x160/0x720 kernel/locking/lockdep.c:4959 __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 seq_read+0x60/0xce0 fs/seq_file.c:155 do_loop_readv_writev fs/read_write.c:734 [inline] do_iter_read+0x44b/0x550 fs/read_write.c:955 vfs_readv+0xc2/0x120 fs/read_write.c:1073 kernel_readv fs/splice.c:355 [inline] default_file_splice_read+0x579/0xa40 fs/splice.c:412 do_splice_to fs/splice.c:871 [inline] splice_direct_to_actor+0x3de/0xb60 fs/splice.c:950 do_splice_direct+0x201/0x340 fs/splice.c:1059 do_sendfile+0x809/0xfe0 fs/read_write.c:1540 __do_sys_sendfile64 fs/read_write.c:1601 [inline] __se_sys_sendfile64 fs/read_write.c:1587 [inline] __x64_sys_sendfile64+0x164/0x1a0 fs/read_write.c:1587 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384 entry_SYSCALL_64_after_hwframe+0x44/0xa9 other info that might help us debug this: Chain exists of: &p->lock --> &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(&p->lock); *** DEADLOCK *** 1 lock held by syz-executor.0/4341: #0: ffff8880a8d74450 (sb_writers#4){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2918 [inline] #0: ffff8880a8d74450 (sb_writers#4){.+.+}-{0:0}, at: do_sendfile+0x7dd/0xfe0 fs/read_write.c:1539 stack backtrace: CPU: 0 PID: 4341 Comm: syz-executor.0 Not tainted 5.8.0-rc7-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+0x1f0/0x31e 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/0x8920 kernel/locking/lockdep.c:3218 __lock_acquire+0x116c/0x2c30 kernel/locking/lockdep.c:4380 lock_acquire+0x160/0x720 kernel/locking/lockdep.c:4959 __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 seq_read+0x60/0xce0 fs/seq_file.c:155 do_loop_readv_writev fs/read_write.c:734 [inline] do_iter_read+0x44b/0x550 fs/read_write.c:955 vfs_readv+0xc2/0x120 fs/read_write.c:1073 kernel_readv fs/splice.c:355 [inline] default_file_splice_read+0x579/0xa40 fs/splice.c:412 do_splice_to fs/splice.c:871 [inline] splice_direct_to_actor+0x3de/0xb60 fs/splice.c:950 do_splice_direct+0x201/0x340 fs/splice.c:1059 do_sendfile+0x809/0xfe0 fs/read_write.c:1540 __do_sys_sendfile64 fs/read_write.c:1601 [inline] __se_sys_sendfile64 fs/read_write.c:1587 [inline] __x64_sys_sendfile64+0x164/0x1a0 fs/read_write.c:1587 do_syscall_64+0x73/0xe0 arch/x86/entry/common.c:384 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x45cc79 Code: 2d 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 fb b5 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fec6bf38c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 0000000000026b80 RCX: 000000000045cc79 RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000005 RBP: 000000000078bf48 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000283 R11: 0000000000000246 R12: 000000000078bf0c R13: 00007ffc9e88f0df R14: 00007fec6bf399c0 R15: 000000000078bf0c