KCSAN: data-race in fuse_lock_inode / process_init_reply

From: syzbot <syzbot+e9c2dec6b40030f721c6@syzkaller.appspotmail.com>
To: elver@google.com, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, miklos@szeredi.hu,
	syzkaller-bugs@googlegroups.com
Subject: KCSAN: data-race in fuse_lock_inode / process_init_reply
Date: Fri, 03 Apr 2020 05:36:15 -0700	[thread overview]
Message-ID: <000000000000cc687e05a26229d2@google.com> (raw)

Hello,

syzbot found the following crash on:

HEAD commit:    245a4300 Merge branch 'rcu/kcsan' into tip/locking/kcsan
git tree:       https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=12a7d9a5e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a4b9db179318d21f
dashboard link: https://syzkaller.appspot.com/bug?extid=e9c2dec6b40030f721c6
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+e9c2dec6b40030f721c6@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in fuse_lock_inode / process_init_reply

read to 0xffff888099cc4d2d of 1 bytes by task 14548 on cpu 1:
 fuse_lock_inode+0x4c/0x90 fs/fuse/inode.c:351
 fuse_lookup+0x3f/0x210 fs/fuse/dir.c:389
 __lookup_hash+0xcb/0x110 fs/namei.c:1544
 filename_create+0x102/0x2d0 fs/namei.c:3639
 user_path_create fs/namei.c:3696 [inline]
 do_linkat+0xff/0x640 fs/namei.c:4298
 __do_sys_link fs/namei.c:4342 [inline]
 __se_sys_link fs/namei.c:4340 [inline]
 __x64_sys_link+0x47/0x60 fs/namei.c:4340
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff888099cc4d2d of 6 bytes by task 14532 on cpu 0:
 process_init_reply+0x7a/0xb90 fs/fuse/inode.c:891
 fuse_request_end+0x324/0x530 fs/fuse/dev.c:328
 end_requests+0x100/0x160 fs/fuse/dev.c:2056
 fuse_abort_conn+0x737/0x7d0 fs/fuse/dev.c:2151
 fuse_dev_release+0x26b/0x290 fs/fuse/dev.c:2186
 __fput+0x1e1/0x520 fs/file_table.c:280
 ____fput+0x1f/0x30 fs/file_table.c:313
 task_work_run+0xf6/0x130 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2b4/0x2c0 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
 do_syscall_64+0x384/0x3a0 arch/x86/entry/common.c:304
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 14532 Comm: syz-executor.1 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

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