linux-ext4 - Re: [PATCH 7/7] libext2fs: check for invalid blocks in ext2fs_punch

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Date:   Tue, 7 Jun 2022 16:22:48 +0200
From:   Lukas Czerner <lczerner@...hat.com>
To:     Theodore Ts'o <tytso@....edu>
Cc:     Ext4 Developers List <linux-ext4@...r.kernel.org>,
        Nils Bars <nils.bars@....de>,
        Moritz Schlögel <moritz.schloegel@....de>,
        Nico Schiller <nico.schiller@....de>
Subject: Re: [PATCH 7/7] libext2fs: check for invalid blocks in
 ext2fs_punch_blocks()

Looks good.

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


Thanks!
-Lukas

On Tue, Jun 07, 2022 at 12:24:44AM -0400, Theodore Ts'o wrote:
> If the extent tree has out-of-range physical block numbers, don't try
> to release them.
> 
> Also add a similar check in ext2fs_block_alloc_stats2() to avoid a
> NULL pointer dereference.
> 
> Reported-by: Nils Bars <nils.bars@....de>
> Reported-by: Moritz Schlögel <moritz.schloegel@....de>
> Reported-by: Nico Schiller <nico.schiller@....de>
> Signed-off-by: Theodore Ts'o <tytso@....edu>
> ---
>  lib/ext2fs/alloc_stats.c | 3 ++-
>  lib/ext2fs/punch.c       | 4 ++++
>  2 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/ext2fs/alloc_stats.c b/lib/ext2fs/alloc_stats.c
> index 3949f618..6f98bcc7 100644
> --- a/lib/ext2fs/alloc_stats.c
> +++ b/lib/ext2fs/alloc_stats.c
> @@ -62,7 +62,8 @@ void ext2fs_block_alloc_stats2(ext2_filsys fs, blk64_t blk, int inuse)
>  {
>  	int	group = ext2fs_group_of_blk2(fs, blk);
>  
> -	if (blk >= ext2fs_blocks_count(fs->super)) {
> +	if (blk < fs->super->s_first_data_block ||
> +	    blk >= ext2fs_blocks_count(fs->super)) {
>  #ifndef OMIT_COM_ERR
>  		com_err("ext2fs_block_alloc_stats", 0,
>  			"Illegal block number: %lu", (unsigned long) blk);
> diff --git a/lib/ext2fs/punch.c b/lib/ext2fs/punch.c
> index effa1e2d..e2543e1e 100644
> --- a/lib/ext2fs/punch.c
> +++ b/lib/ext2fs/punch.c
> @@ -200,6 +200,10 @@ static errcode_t punch_extent_blocks(ext2_filsys fs, ext2_ino_t ino,
>  	__u32		cluster_freed;
>  	errcode_t	retval = 0;
>  
> +	if (free_start < fs->super->s_first_data_block ||
> +	    (free_start + free_count) >= ext2fs_blocks_count(fs->super))
> +		return EXT2_ET_BAD_BLOCK_NUM;
> +
>  	/* No bigalloc?  Just free each block. */
>  	if (EXT2FS_CLUSTER_RATIO(fs) == 1) {
>  		*freed += free_count;
> -- 
> 2.31.0
>