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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Mon, 24 Apr 2023 09:40:03 +0200
Message-ID: <CACT4Y+ZyBsAhdE3joUMQ+AtPukws3kDMirAKBqGg+VXgZKEpQQ@mail.gmail.com>
Subject: Re: [syzbot] [block?] KCSAN: data-race in __filemap_add_folio /
 invalidate_bdev (3)
To:     syzbot <syzbot+8a416e3cb063d4787b0f@syzkaller.appspotmail.com>
Cc:     axboe@kernel.dk, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com
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On Mon, 24 Apr 2023 at 09:20, syzbot
<syzbot+8a416e3cb063d4787b0f@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    3e7bb4f24617 Merge tag '6.3-rc6-smb311-client-negcontext-f..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13c2e6ebc80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=710057cbb8def08c
> dashboard link: https://syzkaller.appspot.com/bug?extid=8a416e3cb063d4787b0f
> compiler:       Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/d1f21f86a5e7/disk-3e7bb4f2.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/5769a034d50c/vmlinux-3e7bb4f2.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/82288ce4b761/bzImage-3e7bb4f2.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+8a416e3cb063d4787b0f@syzkaller.appspotmail.com

invalidate_bdev() looks at mapping->nrpages to decide to
invalidate/not-invalidate. If it's updated concurrently, can't
invalidate_bdev() falsely decide to not invalidate?


> ==================================================================
> BUG: KCSAN: data-race in __filemap_add_folio / invalidate_bdev
>
> read-write to 0xffff8881023fec48 of 8 bytes by task 5672 on cpu 1:
>  __filemap_add_folio+0x38c/0x720 mm/filemap.c:904
>  filemap_add_folio+0x6f/0x150 mm/filemap.c:939
>  filemap_create_folio mm/filemap.c:2545 [inline]
>  filemap_get_pages+0x5d2/0xea0 mm/filemap.c:2605
>  filemap_read+0x223/0x680 mm/filemap.c:2693
>  blkdev_read_iter+0x2ca/0x370 block/fops.c:606
>  call_read_iter include/linux/fs.h:1845 [inline]
>  new_sync_read fs/read_write.c:389 [inline]
>  vfs_read+0x39a/0x560 fs/read_write.c:470
>  ksys_read+0xeb/0x1a0 fs/read_write.c:613
>  __do_sys_read fs/read_write.c:623 [inline]
>  __se_sys_read fs/read_write.c:621 [inline]
>  __x64_sys_read+0x42/0x50 fs/read_write.c:621
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> read to 0xffff8881023fec48 of 8 bytes by task 3141 on cpu 0:
>  invalidate_bdev+0x35/0x80 block/bdev.c:84
>  bdev_disk_changed+0x102/0xbb0 block/partitions/core.c:668
>  __loop_clr_fd+0x2b9/0x3b0 drivers/block/loop.c:1189
>  loop_clr_fd drivers/block/loop.c:1257 [inline]
>  lo_ioctl+0xe9e/0x12f0 drivers/block/loop.c:1563
>  blkdev_ioctl+0x3a0/0x490 block/ioctl.c:615
>  vfs_ioctl fs/ioctl.c:51 [inline]
>  __do_sys_ioctl fs/ioctl.c:870 [inline]
>  __se_sys_ioctl+0xc9/0x140 fs/ioctl.c:856
>  __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:856
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> value changed: 0x0000000000000000 -> 0x0000000000000001
>
> Reported by Kernel Concurrency Sanitizer on:
> CPU: 0 PID: 3141 Comm: syz-executor.2 Not tainted 6.3.0-rc6-syzkaller-00188-g3e7bb4f24617 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
> ==================================================================
>
>
> ---
> 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.
>
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