possible deadlock in proc_tgid_io_accounting (2)

syzbot
2020-09-10T23:19:24Z

Hello,

syzbot found the following issue on:

HEAD commit: dd9fb9bb Merge tags 'auxdisplay-for-linus-v5.9-rc4', 'clan..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=156d617d900000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1c560d0f4e121c9
dashboard link: https://syzkaller.appspot.com/bug?extid=c8e92098d59682aeb2e3
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+c8e92098d59682aeb2e3@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
5.9.0-rc3-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor.2/12039 is trying to acquire lock:
ffff888051129588 (&sig->exec_update_mutex){+.+.}-{3:3}, at: do_io_accounting fs/proc/base.c:2928 [inline]
ffff888051129588 (&sig->exec_update_mutex){+.+.}-{3:3}, at: proc_tgid_io_accounting+0x164/0x580 fs/proc/base.c:2977

but task is already holding lock:
ffff88809e4c6498 (&p->lock){+.+.}-{3:3}, at: seq_read+0x60/0xce0 fs/seq_file.c:155

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #3 (&p->lock){+.+.}-{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_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+0x438/0x620 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+0x86d/0x1210 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+0x31/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

-> #2 (sb_writers#7){.+.+}-{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_xattr_set+0x60/0x3f0 fs/overlayfs/inode.c:344
ovl_posix_acl_xattr_set+0x3c4/0x7a0 fs/overlayfs/super.c:962
__vfs_setxattr+0x3be/0x400 fs/xattr.c:177
__vfs_setxattr_noperm+0x11e/0x4b0 fs/xattr.c:208
vfs_setxattr+0xde/0x270 fs/xattr.c:283
setxattr+0x167/0x350 fs/xattr.c:548
path_setxattr+0x109/0x1c0 fs/xattr.c:567
__do_sys_lsetxattr fs/xattr.c:589 [inline]
__se_sys_lsetxattr fs/xattr.c:585 [inline]
__x64_sys_lsetxattr+0xb4/0xd0 fs/xattr.c:585
do_syscall_64+0x31/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

-> #1 (&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

-> #0 (&sig->exec_update_mutex){+.+.}-{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_killable_nested+0x1a/0x20 kernel/locking/mutex.c:1133
do_io_accounting fs/proc/base.c:2928 [inline]
proc_tgid_io_accounting+0x164/0x580 fs/proc/base.c:2977
proc_single_show+0xf6/0x180 fs/proc/base.c:775
seq_read+0x41a/0xce0 fs/seq_file.c:208
do_loop_readv_writev fs/read_write.c:734 [inline]
do_iter_read+0x438/0x620 fs/read_write.c:955
vfs_readv fs/read_write.c:1073 [inline]
do_preadv+0x17b/0x290 fs/read_write.c:1165
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:
&sig->exec_update_mutex --> sb_writers#7 --> &p->lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&p->lock);
lock(sb_writers#7);
lock(&p->lock);
lock(&sig->exec_update_mutex);

*** DEADLOCK ***

1 lock held by syz-executor.2/12039:
#0: ffff88809e4c6498 (&p->lock){+.+.}-{3:3}, at: seq_read+0x60/0xce0 fs/seq_file.c:155

stack backtrace:
CPU: 0 PID: 12039 Comm: syz-executor.2 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_killable_nested+0x1a/0x20 kernel/locking/mutex.c:1133
do_io_accounting fs/proc/base.c:2928 [inline]
proc_tgid_io_accounting+0x164/0x580 fs/proc/base.c:2977
proc_single_show+0xf6/0x180 fs/proc/base.c:775
seq_read+0x41a/0xce0 fs/seq_file.c:208
do_loop_readv_writev fs/read_write.c:734 [inline]
do_iter_read+0x438/0x620 fs/read_write.c:955
vfs_readv fs/read_write.c:1073 [inline]
do_preadv+0x17b/0x290 fs/read_write.c:1165
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:00007f2c49358c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 0000000000025880 RCX: 000000000045d5b9
RDX: 0000000000000375 RSI: 00000000200017c0 RDI: 0000000000000005
RBP: 000000000118d030 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cfec
R13: 00007ffc04a7470f R14: 00007f2c493599c0 R15: 000000000118cfec

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