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Date: Sat, 02 Dec 2017 00:12:01 -0800
From: syzbot
<bot+e93a80c1bb7c5c56e522461c149f8bf55eab1b2b@...kaller.appspotmail.com>
To: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
syzkaller-bugs@...glegroups.com, viro@...iv.linux.org.uk
Subject: possible deadlock in seq_read
syzkaller has found reproducer for the following crash on
4131d5166185d0d75b5f1d4bf362a9e0bac05598
git://git.cmpxchg.org/linux-mmots.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers
binder: 3116:3117 transaction failed 29189/-22, size 0-0 line 2832
======================================================
WARNING: possible circular locking dependency detected
4.15.0-rc1-mm1+ #29 Not tainted
------------------------------------------------------
syz-executor0/3121 is trying to acquire lock:
(&p->lock){+.+.}, at: [<00000000a7751419>] seq_read+0xd5/0x13d0
fs/seq_file.c:165
but task is already holding lock:
(sb_writers){.+.+}, at: [<00000000048429cb>] file_start_write
include/linux/fs.h:2715 [inline]
(sb_writers){.+.+}, at: [<00000000048429cb>] do_sendfile+0xaec/0xe90
fs/read_write.c:1412
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #3 (sb_writers){.+.+}:
spin_lock include/linux/spinlock.h:315 [inline]
devtmpfsd+0x224/0x4b0 drivers/base/devtmpfs.c:392
-> #2 ((completion)&req.done){+.+.}:
lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4004
complete_acquire include/linux/completion.h:40 [inline]
__wait_for_common kernel/sched/completion.c:109 [inline]
wait_for_common kernel/sched/completion.c:123 [inline]
wait_for_completion+0xcb/0x7b0 kernel/sched/completion.c:144
devtmpfs_create_node+0x32b/0x4a0 drivers/base/devtmpfs.c:115
device_add+0x120f/0x1640 drivers/base/core.c:1824
device_create_groups_vargs+0x1f3/0x250 drivers/base/core.c:2430
device_create_vargs drivers/base/core.c:2470 [inline]
device_create+0xda/0x110 drivers/base/core.c:2506
vcs_make_sysfs+0x35/0x60 drivers/tty/vt/vc_screen.c:629
vc_allocate+0x4b7/0x6b0 drivers/tty/vt/vt.c:797
con_install+0x52/0x440 drivers/tty/vt/vt.c:2876
tty_driver_install_tty drivers/tty/tty_io.c:1215 [inline]
tty_init_dev+0xf6/0x4a0 drivers/tty/tty_io.c:1315
tty_open_by_driver drivers/tty/tty_io.c:1942 [inline]
tty_open+0x608/0xab0 drivers/tty/tty_io.c:1990
chrdev_open+0x257/0x730 fs/char_dev.c:417
do_dentry_open+0x682/0xd70 fs/open.c:752
vfs_open+0x107/0x230 fs/open.c:866
do_last fs/namei.c:3379 [inline]
path_openat+0x1157/0x3530 fs/namei.c:3519
do_filp_open+0x25b/0x3b0 fs/namei.c:3554
do_sys_open+0x502/0x6d0 fs/open.c:1059
SYSC_open fs/open.c:1077 [inline]
SyS_open+0x2d/0x40 fs/open.c:1072
entry_SYSCALL_64_fastpath+0x1f/0x96
-> #1 (console_lock){+.+.}:
lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4004
console_lock+0x4b/0x80 kernel/printk/printk.c:2047
c_start+0x18/0xf0 arch/x86/kernel/cpu/proc.c:146
seq_read+0x2f3/0x13d0 fs/seq_file.c:229
proc_reg_read+0xef/0x170 fs/proc/inode.c:217
__vfs_read+0xef/0xa00 fs/read_write.c:411
vfs_read+0x124/0x360 fs/read_write.c:447
SYSC_read fs/read_write.c:573 [inline]
SyS_read+0xef/0x220 fs/read_write.c:566
entry_SYSCALL_64_fastpath+0x1f/0x96
-> #0 (&p->lock){+.+.}:
check_prevs_add kernel/locking/lockdep.c:2031 [inline]
validate_chain kernel/locking/lockdep.c:2473 [inline]
__lock_acquire+0x3498/0x47f0 kernel/locking/lockdep.c:3500
lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4004
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
seq_read+0xd5/0x13d0 fs/seq_file.c:165
proc_reg_read+0xef/0x170 fs/proc/inode.c:217
do_loop_readv_writev fs/read_write.c:673 [inline]
do_iter_read+0x3db/0x5b0 fs/read_write.c:897
vfs_readv+0x121/0x1c0 fs/read_write.c:959
kernel_readv fs/splice.c:361 [inline]
default_file_splice_read+0x508/0xae0 fs/splice.c:416
do_splice_to+0x110/0x170 fs/splice.c:880
splice_direct_to_actor+0x242/0x820 fs/splice.c:952
do_splice_direct+0x2a7/0x3d0 fs/splice.c:1061
do_sendfile+0x5d5/0xe90 fs/read_write.c:1413
SYSC_sendfile64 fs/read_write.c:1468 [inline]
SyS_sendfile64+0xbd/0x160 fs/read_write.c:1460
entry_SYSCALL_64_fastpath+0x1f/0x96
other info that might help us debug this:
Chain exists of:
&p->lock --> (completion)&req.done --> sb_writers
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(sb_writers);
lock((completion)&req.done);
lock(sb_writers);
lock(&p->lock);
*** DEADLOCK ***
1 lock held by syz-executor0/3121:
#0: (sb_writers){.+.+}, at: [<00000000048429cb>] file_start_write
include/linux/fs.h:2715 [inline]
#0: (sb_writers){.+.+}, at: [<00000000048429cb>] do_sendfile+0xaec/0xe90
fs/read_write.c:1412
stack backtrace:
CPU: 0 PID: 3121 Comm: syz-executor0 Not tainted 4.15.0-rc1-mm1+ #29
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
print_circular_bug+0x42d/0x610 kernel/locking/lockdep.c:1271
check_prev_add+0x666/0x15f0 kernel/locking/lockdep.c:1914
check_prevs_add kernel/locking/lockdep.c:2031 [inline]
validate_chain kernel/locking/lockdep.c:2473 [inline]
__lock_acquire+0x3498/0x47f0 kernel/locking/lockdep.c:3500
lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4004
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
seq_read+0xd5/0x13d0 fs/seq_file.c:165
proc_reg_read+0xef/0x170 fs/proc/inode.c:217
do_loop_readv_writev fs/read_write.c:673 [inline]
do_iter_read+0x3db/0x5b0 fs/read_write.c:897
vfs_readv+0x121/0x1c0 fs/read_write.c:959
kernel_readv fs/splice.c:361 [inline]
default_file_splice_read+0x508/0xae0 fs/splice.c:416
do_splice_to+0x110/0x170 fs/splice.c:880
splice_direct_to_actor+0x242/0x820 fs/splice.c:952
do_splice_direct+0x2a7/0x3d0 fs/splice.c:1061
do_sendfile+0x5d5/0xe90 fs/read_write.c:1413
SYSC_sendfile64 fs/read_write.c:1468 [inline]
SyS_sendfile64+0xbd/0x160 fs/read_write.c:1460
entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x4529d9
RSP: 002b:00007fce2efc6c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00000000007580d8 RCX: 00000000004529d9
RDX: 00000000203e1000 RSI: 000000000000000e RDI: 000000000000000d
RBP: 000000000000044a R08: 0000000000000000 R09: 0000000000000000
R10: 00000000000003fe R11: 0000000000000212 R12: 00000000006f3790
View attachment "config.txt" of type "text/plain" (126531 bytes)
Download attachment "raw.log" of type "application/octet-stream" (10272 bytes)
View attachment "repro.txt" of type "text/plain" (6527 bytes)
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