On Sat 15-05-21 00:23:35, Pavel Skripkin wrote:
> syzbot reported divide error in reiserfs.
> The problem was in incorrect journal 1st block.
>
> Syzbot's reproducer manualy generated wrong superblock
> with incorrect 1st block. In journal_init() wasn't
> any checks about this particular case.
>
> For example, if 1st journal block is before superblock
> 1st block, it can cause zeroing important superblock members
> in do_journal_end().
>
> Reported-and-tested-by: syzbot+0ba9909df31c6a36974d@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Pavel Skripkin <paskripkin@xxxxxxxxx>
Thanks for the patch. One comment below:
> diff --git a/fs/reiserfs/journal.c b/fs/reiserfs/journal.c
> index 9edc8e2b154e..d58f24a08385 100644
> --- a/fs/reiserfs/journal.c
> +++ b/fs/reiserfs/journal.c
> @@ -2758,6 +2758,19 @@ int journal_init(struct super_block *sb, const char *j_dev_name,
> goto free_and_return;
> }
>
> + /*
> + * Sanity check to see is journal first block correct.
> + * If journal first block is invalid it can cause
> + * zeroing important superblock members.
> + */
> + if (SB_ONDISK_JOURNAL_1st_BLOCK(sb) < SB_JOURNAL_1st_RESERVED_BLOCK(sb)) {
I guess this check is valid only if !SB_ONDISK_JOURNAL_DEVICE(sb), isn't
it? Otherwise you are comparing block numbers from two different devices...
Honza
> + reiserfs_warning(sb, "journal-1393",
> + "journal 1st super block is invalid: 1st reserved block %d, but actual 1st block is %d",
> + SB_JOURNAL_1st_RESERVED_BLOCK(sb),
> + SB_ONDISK_JOURNAL_1st_BLOCK(sb));
> + goto free_and_return;
> + }
> +
> if (journal_init_dev(sb, journal, j_dev_name) != 0) {
> reiserfs_warning(sb, "sh-462",
> "unable to initialize journal device");
> --
> 2.31.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
