linux-kernel - Re: [PATCH] Fix out-of-bounds access in xfs_bmapi

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Message-ID: <Zx9PTso9Me5es7He@infradead.org>
Date: Mon, 28 Oct 2024 01:46:06 -0700
From: Christoph Hellwig <hch@...radead.org>
To: MottiKumar Babu <mottikumarbabu@...il.com>
Cc: cem@...nel.org, djwong@...nel.org, chandanbabu@...nel.org,
	dchinner@...hat.com, zhangjiachen.jaycee@...edance.com,
	linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-kernel-mentees@...ts.linux.dev, anupnewsmail@...il.com,
	skhan@...uxfoundation.org
Subject: Re: [PATCH] Fix out-of-bounds access in xfs_bmapi_allocate by
 validating whichfork

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@...il.com>
> ---
>  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?