linux-kernel - Re: [PATCH] udf: KASAN: slab-out-of-bounds in udf

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Date:   Tue, 7 Feb 2023 13:44:47 +0100
From:   Jan Kara <jack@...e.cz>
To:     Vladislav Efanov <VEfanov@...ras.ru>
Cc:     Jan Kara <jack@...e.com>, linux-kernel@...r.kernel.org,
        lvc-project@...uxtesting.org
Subject: Re: [PATCH] udf: KASAN: slab-out-of-bounds in udf_readdir

On Mon 06-02-23 19:22:06, Vladislav Efanov wrote:
> The KASAN report is:
> [ 1922.586560] BUG: KASAN: slab-out-of-bounds in udf_readdir+0xe00/0x19e0
> [ 1922.586922] Write of size 89 at addr ffff888000cd9ea6 by task rm/18493
> 
> udf_readdir() tries to write file name out of allocated memory
> buffer bounds. The UDF_NAME_LEN_CS0 (255) is used as max length
> for file name in udf_put_filename(). But UDF_NAME_LEN (254) is
> used as the size for buffer allocation in udf_readdir(). As the
> result out-of-bounds write happened.
> 
> Found by Linux Verification Center (linuxtesting.org) with xfstests
> 
> Fixes: 066b9cded00b ("udf: Use separate buffer for copying split names")
> Signed-off-by: Vladislav Efanov <VEfanov@...ras.ru>

Thanks for the fix Vladislav! But this code is not there anymore in current
version of UDF code. It got fixed as part of the directory code rewrite -
you can check current code state in my tree:

git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs.git for_next

								Honza

> ---
>  fs/udf/dir.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/udf/dir.c b/fs/udf/dir.c
> index be640f4b2f2c..b95607c42ad4 100644
> --- a/fs/udf/dir.c
> +++ b/fs/udf/dir.c
> @@ -169,7 +169,7 @@ static int udf_readdir(struct file *file, struct dir_context *ctx)
>  				nameptr = (char *)(fibh.ebh->b_data + poffset - lfi);
>  			} else {
>  				if (!copy_name) {
> -					copy_name = kmalloc(UDF_NAME_LEN,
> +					copy_name = kmalloc(UDF_NAME_LEN_CS0,
>  							    GFP_NOFS);
>  					if (!copy_name) {
>  						ret = -ENOMEM;
> -- 
> 2.34.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR