Re: [PATCH] btrfs: add a sanity check for csum root before fill the data csum

[Qu Wenruo]

在 2024/10/23 21:34, Edward Adam Davis 写道:
> Syzbot reported a null-ptr-deref in btrfs_lookup_csums_bitmap.
> The btrfs info contains IGNOREDATACSUMS, which prevents the csum root from
> being loaded.
> Before filling in the csum data, check the flag BTRFS_FS_STATE_NO_DATA_CSUMS
> to confirm that the csum root has been loaded.
>
> Reported-and-tested-by: syzbot+5d2b33d7835870519b5f@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=5d2b33d7835870519b5f
> Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>

Reviewed-by: Qu Wenruo <wqu@xxxxxxxx>

Thanks,
Qu

> ---
>   fs/btrfs/scrub.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index 3a3427428074..1ba4d8ba902b 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -1602,7 +1602,8 @@ static int scrub_find_fill_first_stripe(struct btrfs_block_group *bg,
>   	}
>
>   	/* Now fill the data csum. */
> -	if (bg->flags & BTRFS_BLOCK_GROUP_DATA) {
> +	if (!test_bit(BTRFS_FS_STATE_NO_DATA_CSUMS, &fs_info->fs_state) &&
> +	    bg->flags & BTRFS_BLOCK_GROUP_DATA) {
>   		int sector_nr;
>   		unsigned long csum_bitmap = 0;