Re: [PATCH] blk-crypto: Add check for mempool_alloc()

[Eric Biggers]

On Thu, Jan 02, 2025 at 04:33:19PM +0800, Haoxiang Li wrote:
> Add check for the return value of mempool_alloc() to
> catch the potential exception and avoid null pointer
> dereference.
> 
> Fixes: 488f6682c832 ("block: blk-crypto-fallback for Inline Encryption")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Haoxiang Li <haoxiang_li2024@xxxxxxx>
> ---
>  block/blk-crypto-fallback.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/block/blk-crypto-fallback.c b/block/blk-crypto-fallback.c
> index 29a205482617..47acd7a48767 100644
> --- a/block/blk-crypto-fallback.c
> +++ b/block/blk-crypto-fallback.c
> @@ -514,6 +514,12 @@ bool blk_crypto_fallback_bio_prep(struct bio **bio_ptr)
>  	 * bi_end_io appropriately to trigger decryption when the bio is ended.
>  	 */
>  	f_ctx = mempool_alloc(bio_fallback_crypt_ctx_pool, GFP_NOIO);
> +
> +	if (!f_ctx) {
> +		bio->bi_status = BLK_STS_RESOURCE;
> +		return false;
> +	}

mempool_alloc() with a mask that includes ___GFP_DIRECT_RECLAIM, such as the
GFP_NOIO which is used here, never returns NULL.

- Eric