[syzbot] [overlayfs?] possible deadlock in seq_read_iter (4)

From: syzbot
Date: Mon May 27 2024 - 02:47:30 EST

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Hello,

syzbot found the following issue on:

HEAD commit: b6394d6f7159 Merge tag 'pull-misc' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=135d2872980000
kernel config: https://syzkaller.appspot.com/x/.config?x=713476114e57eef3
dashboard link: https://syzkaller.appspot.com/bug?extid=fcdd1f09adf0e00f70b1
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e8e1377d4772/disk-b6394d6f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/19fbbb3b6dd5/vmlinux-b6394d6f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4dcce16af95d/bzImage-b6394d6f.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fcdd1f09adf0e00f70b1@xxxxxxxxxxxxxxxxxxxxxxxxx

EXT4-fs (loop3): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: writeback.
ext4 filesystem being mounted at /root/syzkaller-testdir1425634012/syzkaller.WKKmVT/16/bus supports timestamps until 2038-01-19 (0x7fffffff)
======================================================
WARNING: possible circular locking dependency detected
6.9.0-syzkaller-10729-gb6394d6f7159 #0 Not tainted
------------------------------------------------------
syz-executor.3/6567 is trying to acquire lock:
ffff88805cad90a0 (&p->lock){+.+.}-{3:3}, at: seq_read_iter+0xb7/0xd60 fs/seq_file.c:182

but task is already holding lock:
ffff88801eec3c68 (&pipe->mutex){+.+.}-{3:3}, at: splice_file_to_pipe+0x2e/0x500 fs/splice.c:1292

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #4 (&pipe->mutex){+.+.}-{3:3}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
iter_file_splice_write+0x335/0x14e0 fs/splice.c:687
do_splice_from fs/splice.c:941 [inline]
do_splice+0xd77/0x1900 fs/splice.c:1354
__do_splice fs/splice.c:1436 [inline]
__do_sys_splice fs/splice.c:1652 [inline]
__se_sys_splice+0x331/0x4a0 fs/splice.c:1634
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #3 (sb_writers#4){.+.+}-{0:0}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1655 [inline]
sb_start_write+0x4d/0x1c0 include/linux/fs.h:1791
mnt_want_write+0x3f/0x90 fs/namespace.c:409
ovl_setattr+0x2de/0x5a0 fs/overlayfs/inode.c:77
notify_change+0xb9d/0xe70 fs/attr.c:497
vfs_utimes+0x4b5/0x770 fs/utimes.c:66
do_utimes_path fs/utimes.c:99 [inline]
do_utimes fs/utimes.c:145 [inline]
__do_sys_utime fs/utimes.c:226 [inline]
__se_sys_utime+0x1e1/0x2e0 fs/utimes.c:215
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (&ovl_i_mutex_dir_key[depth]#2){++++}-{3:3}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
down_read+0xb1/0xa40 kernel/locking/rwsem.c:1526
inode_lock_shared include/linux/fs.h:801 [inline]
lookup_slow+0x45/0x70 fs/namei.c:1708
walk_component+0x2e1/0x410 fs/namei.c:2004
lookup_last fs/namei.c:2469 [inline]
path_lookupat+0x16f/0x450 fs/namei.c:2493
filename_lookup+0x256/0x610 fs/namei.c:2522
kern_path+0x35/0x50 fs/namei.c:2630
lookup_bdev+0xc5/0x290 block/bdev.c:1157
resume_store+0x1a0/0x710 kernel/power/hibernate.c:1235
kernfs_fop_write_iter+0x3a1/0x500 fs/kernfs/file.c:334
new_sync_write fs/read_write.c:497 [inline]
vfs_write+0xa72/0xc90 fs/read_write.c:590
ksys_write+0x1a0/0x2c0 fs/read_write.c:643
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&of->mutex){+.+.}-{3:3}:
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
kernfs_seq_start+0x53/0x3b0 fs/kernfs/file.c:154
seq_read_iter+0x3d0/0xd60 fs/seq_file.c:225
copy_splice_read+0x662/0xb60 fs/splice.c:365
do_splice_read fs/splice.c:985 [inline]
splice_direct_to_actor+0x4b7/0xc90 fs/splice.c:1089
do_splice_direct_actor fs/splice.c:1207 [inline]
do_splice_direct+0x28c/0x3e0 fs/splice.c:1233
do_sendfile+0x56d/0xe10 fs/read_write.c:1295
__do_sys_sendfile64 fs/read_write.c:1362 [inline]
__se_sys_sendfile64+0x17c/0x1e0 fs/read_write.c:1348
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&p->lock){+.+.}-{3:3}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
seq_read_iter+0xb7/0xd60 fs/seq_file.c:182
copy_splice_read+0x662/0xb60 fs/splice.c:365
do_splice_read fs/splice.c:985 [inline]
splice_file_to_pipe+0x299/0x500 fs/splice.c:1295
do_sendfile+0x515/0xe10 fs/read_write.c:1301
__do_sys_sendfile64 fs/read_write.c:1362 [inline]
__se_sys_sendfile64+0x17c/0x1e0 fs/read_write.c:1348
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
&p->lock --> sb_writers#4 --> &pipe->mutex

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&pipe->mutex);
lock(sb_writers#4);
lock(&pipe->mutex);
lock(&p->lock);

*** DEADLOCK ***

1 lock held by syz-executor.3/6567:
#0: ffff88801eec3c68 (&pipe->mutex){+.+.}-{3:3}, at: splice_file_to_pipe+0x2e/0x500 fs/splice.c:1292

stack backtrace:
CPU: 1 PID: 6567 Comm: syz-executor.3 Not tainted 6.9.0-syzkaller-10729-gb6394d6f7159 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2187
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869
__lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
__mutex_lock_common kernel/locking/mutex.c:608 [inline]
__mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752
seq_read_iter+0xb7/0xd60 fs/seq_file.c:182
copy_splice_read+0x662/0xb60 fs/splice.c:365
do_splice_read fs/splice.c:985 [inline]
splice_file_to_pipe+0x299/0x500 fs/splice.c:1295
do_sendfile+0x515/0xe10 fs/read_write.c:1301
__do_sys_sendfile64 fs/read_write.c:1362 [inline]
__se_sys_sendfile64+0x17c/0x1e0 fs/read_write.c:1348
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fad33e7cee9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 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 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fad34b5b0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007fad33fabf80 RCX: 00007fad33e7cee9
RDX: 0000000000000000 RSI: 0000000000000008 RDI: 000000000000000a
RBP: 00007fad33ec949e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000100801700 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007fad33fabf80 R15: 00007ffed6123a38
</TASK>

---
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Next message: Abel Vesa: "[PATCH] arm64: dts: qcom: x1e80100: Enable tsens and thermal nodes"
Previous message: John Ogness: "[PATCH printk v6 30/30] lockdep: Mark emergency sections in lockdep splats"
Next in thread: Miklos Szeredi: "Re: [syzbot] [overlayfs?] possible deadlock in seq_read_iter (4)"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]