Re: [PATCH] xfs: do not call xfs_buf_hash_destroy on a NULL pag

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Jan 20, 2017 at 02:26:42PM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> If pag cannot be allocated, the current error exit path will trip
> a null pointer deference error when calling xfs_buf_hash_destroy
> with a null pag.  Fix this by adding a new error exit lable and
> jumping to this, avoiding the hash destroy and unnecessary kmem_free
> on pag.
> 
> Fixes CoverityScan CID#1397628 ("Dereference after null check")
> 
> Signed-off-by: Colin Ian King <colin.king@canonical.com>

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

Applied, thanks.

--D

> ---
>  fs/xfs/xfs_mount.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> index 9b9540d..4e66cd19 100644
> --- a/fs/xfs/xfs_mount.c
> +++ b/fs/xfs/xfs_mount.c
> @@ -207,7 +207,7 @@ xfs_initialize_perag(
>  
>  		pag = kmem_zalloc(sizeof(*pag), KM_MAYFAIL);
>  		if (!pag)
> -			goto out_unwind;
> +			goto out_unwind_pags;
>  		pag->pag_agno = index;
>  		pag->pag_mount = mp;
>  		spin_lock_init(&pag->pag_ici_lock);
> @@ -242,6 +242,7 @@ xfs_initialize_perag(
>  out_unwind:
>  	xfs_buf_hash_destroy(pag);
>  	kmem_free(pag);
> +out_unwind_pags:
>  	for (; index > first_initialised; index--) {
>  		pag = radix_tree_delete(&mp->m_perag_tree, index);
>  		xfs_buf_hash_destroy(pag);
> -- 
> 2.10.2
> 
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