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Date:   Tue, 7 Jun 2022 15:12:30 +0200
From:   Lukas Czerner <lczerner@redhat.com>
To:     Theodore Ts'o <tytso@mit.edu>
Cc:     Ext4 Developers List <linux-ext4@vger.kernel.org>,
        Nils Bars <nils.bars@rub.de>,
        Moritz =?utf-8?B?U2NobMO2Z2Vs?= <moritz.schloegel@rub.de>,
        Nico Schiller <nico.schiller@rub.de>
Subject: Re: [PATCH 1/7] e2fsck: sanity check the journal inode number
Message-ID: <20220607131230.vwlqysdihghwwpyx@fedora>
References: <20220607042444.1798015-1-tytso@mit.edu>
 <20220607042444.1798015-2-tytso@mit.edu>
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On Tue, Jun 07, 2022 at 12:24:38AM -0400, Theodore Ts'o wrote:
> E2fsck replays the journal before sanity checking the full superblock.
> So it's possible that the journal inode number is not valid relative
> to the number of block groups.  So to avoid potentially an array
> bounds overrun, sanity check this before trying to find the journal
> inode.

Looks good.

Reviewed-by: Lukas Czerner <lczerner@redhat.com>

> 
> Reported-by: Nils Bars <nils.bars@rub.de>
> Reported-by: Moritz Schl?gel <moritz.schloegel@rub.de>
> Reported-by: Nico Schiller <nico.schiller@rub.de>
> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
> ---
>  e2fsck/journal.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/e2fsck/journal.c b/e2fsck/journal.c
> index 2e867234..12487e3d 100644
> --- a/e2fsck/journal.c
> +++ b/e2fsck/journal.c
> @@ -989,7 +989,14 @@ static errcode_t e2fsck_get_journal(e2fsck_t ctx, journal_t **ret_journal)
>  	journal->j_blocksize = ctx->fs->blocksize;
>  
>  	if (uuid_is_null(sb->s_journal_uuid)) {
> -		if (!sb->s_journal_inum) {
> +		/*
> +		 * The full set of superblock sanity checks haven't
> +		 * been performed yet, so we need to do some basic
> +		 * checks here to avoid potential array overruns.
> +		 */
> +		if (!sb->s_journal_inum ||
> +		    (sb->s_journal_inum >
> +		     (ctx->fs->group_desc_count * sb->s_inodes_per_group))) {
>  			retval = EXT2_ET_BAD_INODE_NUM;
>  			goto errout;
>  		}
> -- 
> 2.31.0
>