Re: [PATCH 3/5] CVE-2025-26723: fs: ext4: fix malloc(size + constant) buffer overflow issues

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 19.02.25 15:18, Sascha Hauer wrote:
> The pattern malloc(size + constant) is dangerous when size can be
> manipulated by an attacker. In that case 'size' can be manipulated
> in a way that 'size + constant' is 0 due to integer overflow. The
> result is a zero sized buffer to which is then data written to.
> 
> Avoid this by using size_add() instead.
> 
> Reported-by: Jonathan Bar Or <jonathanbaror@gmail.com>
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Reviewed-by: Ahmad Fatoum <a.fatoum@pengutronix.de>

> ---
>  fs/ext4/ext_barebox.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/ext4/ext_barebox.c b/fs/ext4/ext_barebox.c
> index 163c4d2fe1..7480c045d7 100644
> --- a/fs/ext4/ext_barebox.c
> +++ b/fs/ext4/ext_barebox.c
> @@ -189,7 +189,7 @@ static const char *ext_get_link(struct dentry *dentry, struct inode *inode)
>  
>  	BUG_ON(inode->i_link);
>  
> -	inode->i_link = zalloc(inode->i_size + 1);
> +	inode->i_link = zalloc(size_add(inode->i_size, 1));
>  
>  	ret = ext4fs_read_file(node, 0, inode->i_size, inode->i_link);
>  	if (ret == 0) {


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