Re: [PATCH] Fix out-of-bounds access in xfs_bmapi_allocate by validating whichfork

[Christoph Hellwig]

On Mon, Oct 28, 2024 at 01:05:27AM +0530, MottiKumar Babu wrote:
> This issue was reported by Coverity Scan.
> 
> Report:
> CID 1633175 Out-of-bounds access - Access of memory not owned by this buffer may cause crashes or incorrect computations.
> In xfs_bmapi_allocate: Out-of-bounds access to a buffer (CWE-119)
> 
> Signed-off-by: MottiKumar Babu <mottikumarbabu@xxxxxxxxx>
> ---
>  fs/xfs/libxfs/xfs_bmap.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index 36dd08d13293..6ff378d2d3d9 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -4169,6 +4169,10 @@ xfs_bmapi_allocate(
>  		 * is not on the busy list.
>  		 */
>  		bma->datatype = XFS_ALLOC_NOBUSY;
> +		// Ensure whichfork is valid (0 or 1) before further checks
> +		if (whichfork < 0 || whichfork > 1) {
> +			return -EINVAL; // Invalid fork

How is this supposed to happen?