linux-kernel - Re: [PATCH] jfs: xattr: check invalid xattr size more strictly

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Message-ID: <d52ae3e1-7ef9-4d31-b463-dec0e2427210@oracle.com>
Date: Tue, 29 Oct 2024 17:18:47 -0500
From: Dave Kleikamp <dave.kleikamp@...cle.com>
To: Artem Sadovnikov <ancowi69@...il.com>
Cc: Christian Brauner <brauner@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        jfs-discussion@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
        lvc-project@...uxtesting.org, stable@...r.kernel.org
Subject: Re: [PATCH] jfs: xattr: check invalid xattr size more strictly

On 10/5/24 5:06AM, Artem Sadovnikov wrote:
> Commit 7c55b78818cf ("jfs: xattr: fix buffer overflow for invalid xattr")
> also addresses this issue but it only fixes it for positive values, while
> ea_size is an integer type and can take negative values, e.g. in case of
> a corrupted filesystem. This still breaks validation and would overflow
> because of implicit conversion from int to size_t in print_hex_dump().
> 
> Fix this issue by clamping the ea_size value instead.
> 
> Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
> 
> Cc: stable@...r.kernel.org
> Signed-off-by: Artem Sadovnikov <ancowi69@...il.com>

Looks good. I'll apply this one.

Shaggy
> ---
>   fs/jfs/xattr.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/jfs/xattr.c b/fs/jfs/xattr.c
> index 8ef8dfc3c194..95bcbbf7359c 100644
> --- a/fs/jfs/xattr.c
> +++ b/fs/jfs/xattr.c
> @@ -557,7 +557,7 @@ static int ea_get(struct inode *inode, struct ea_buffer *ea_buf, int min_size)
>   
>         size_check:
>   	if (EALIST_SIZE(ea_buf->xattr) != ea_size) {
> -		int size = min_t(int, EALIST_SIZE(ea_buf->xattr), ea_size);
> +		int size = clamp_t(int, ea_size, 0, EALIST_SIZE(ea_buf->xattr));
>   
>   		printk(KERN_ERR "ea_get: invalid extended attribute\n");
>   		print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1,