Received-SPF: pass (google.com: domain of linux-ext4-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
Date:   Thu, 11 Mar 2021 02:59:14 -0800
Message-ID: <0000000000008de88005bd40ac36@google.com>
Subject: [syzbot] KCSAN: data-race in start_this_handle / start_this_handle
From:   syzbot <syzbot+30774a6acf6a2cf6d535@syzkaller.appspotmail.com>
To:     jack@suse.com, linux-ext4@vger.kernel.org,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
        tytso@mit.edu
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hello,

syzbot found the following issue on:

HEAD commit:    a74e6a01 Merge tag 's390-5.12-3' of git://git.kernel.org/p..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=159f69ecd00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=de394bbaade74fb7
dashboard link: https://syzkaller.appspot.com/bug?extid=30774a6acf6a2cf6d535
compiler:       Debian clang version 11.0.1-2

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+30774a6acf6a2cf6d535@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in start_this_handle / start_this_handle

write to 0xffff888103880870 of 8 bytes by task 29956 on cpu 1:
 jbd2_get_transaction fs/jbd2/transaction.c:125 [inline]
 start_this_handle+0xceb/0x1010 fs/jbd2/transaction.c:400
 jbd2__journal_start+0x1fc/0x3f0 fs/jbd2/transaction.c:503
 __ext4_journal_start_sb+0x159/0x310 fs/ext4/ext4_jbd2.c:105
 __ext4_journal_start fs/ext4/ext4_jbd2.h:320 [inline]
 ext4_da_write_begin+0x460/0xaf0 fs/ext4/inode.c:2998
 generic_perform_write+0x196/0x3a0 mm/filemap.c:3575
 ext4_buffered_write_iter+0x2e5/0x3e0 fs/ext4/file.c:269
 ext4_file_write_iter+0x48a/0x10b0 fs/ext4/file.c:502
 call_write_iter include/linux/fs.h:1977 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4c0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x40a/0x750 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x7a6/0xe20 fs/read_write.c:1260
 __do_sys_sendfile64 fs/read_write.c:1319 [inline]
 __se_sys_sendfile64 fs/read_write.c:1311 [inline]
 __x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1311
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888103880870 of 8 bytes by task 29936 on cpu 0:
 start_this_handle+0x1c1/0x1010 fs/jbd2/transaction.c:352
 jbd2__journal_start+0x1fc/0x3f0 fs/jbd2/transaction.c:503
 __ext4_journal_start_sb+0x159/0x310 fs/ext4/ext4_jbd2.c:105
 __ext4_journal_start fs/ext4/ext4_jbd2.h:320 [inline]
 ext4_da_write_begin+0x460/0xaf0 fs/ext4/inode.c:2998
 generic_perform_write+0x196/0x3a0 mm/filemap.c:3575
 ext4_buffered_write_iter+0x2e5/0x3e0 fs/ext4/file.c:269
 ext4_file_write_iter+0x48a/0x10b0 fs/ext4/file.c:502
 call_write_iter include/linux/fs.h:1977 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4c0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x40a/0x750 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x7a6/0xe20 fs/read_write.c:1260
 __do_sys_sendfile64 fs/read_write.c:1319 [inline]
 __se_sys_sendfile64 fs/read_write.c:1311 [inline]
 __x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1311
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 29936 Comm: syz-executor.5 Not tainted 5.12.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.