Re: [PATCH][next] mm/zswap: fix potential uninitialized pointer read on tmp

[Vlastimil Babka]

On 1/28/21 3:17 PM, Colin King wrote:
> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> 
> In the case where zpool_can_sleep_mapped(pool) returns 0
> then tmp is not allocated and tmp is then an uninitialized
> pointer. Later if entry is null, tmp is freed, hence free'ing
> an uninitialized pointer. Fix this by ensuring tmp is initialized
> to NULL.
> 
> Addresses-Coverity: ("Uninitialized pointer read")
> Fixes: 908aa806dba0 ("mm/zswap: fix potential memory leak")

That's a linux-next hash, patch is in mmotm [1] *) You know what it means...

*) actually it's not there, yet it is in -next. What's going on?

[1]
https://ozlabs.org/~akpm/mmotm/broken-out/mm-zswap-fix-potential-memory-leak.patch

> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> ---
>  mm/zswap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/zswap.c b/mm/zswap.c
> index 8d1381b1178d..578d9f256920 100644
> --- a/mm/zswap.c
> +++ b/mm/zswap.c
> @@ -935,7 +935,7 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
>  	struct scatterlist input, output;
>  	struct crypto_acomp_ctx *acomp_ctx;
>  
> -	u8 *src, *tmp;
> +	u8 *src, *tmp = NULL;
>  	unsigned int dlen;
>  	int ret;
>  	struct writeback_control wbc = {
>