linux-kernel - Re: [PATCH] lib/lru_cache: Fixed array overflow caused by incorrect boundary handling.

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Date:   Mon, 1 Aug 2022 17:40:52 +0200
From:   Christoph Böhmwalder 
        <christoph.boehmwalder@...bit.com>
To:     John Sanpe <sanpeqf@...il.com>
Cc:     drbd-dev@...ts.linbit.com, linux-kernel@...r.kernel.org,
        philipp.reisner@...bit.com, lars.ellenberg@...bit.com
Subject: Re: [PATCH] lib/lru_cache: Fixed array overflow caused by incorrect
 boundary handling.

Am 23.07.22 um 09:59 schrieb John Sanpe:
> This problem occurs when malloc element failed on the first time.
> At this time, the counter i is 0. When it's released, we subtract 1
> in advance without checking, which will cause i to become UINT_MAX,
> resulting in array overflow.
> 
> Signed-off-by: John Sanpe <sanpeqf@...il.com>
> ---
>  lib/lru_cache.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/lru_cache.c b/lib/lru_cache.c
> index 52313acbfa62..04d95de92602 100644
> --- a/lib/lru_cache.c
> +++ b/lib/lru_cache.c
> @@ -147,7 +147,7 @@ struct lru_cache *lc_create(const char *name, struct kmem_cache *cache,
>  		return lc;
>  
>  	/* else: could not allocate all elements, give up */
> -	for (i--; i; i--) {
> +	while (i--) {
>  		void *p = element[i];
>  		kmem_cache_free(cache, p - e_off);
>  	}

Thanks for the fix, looks good to me.

Reviewed-by: Christoph Böhmwalder <christoph.boehmwalder@...bit.com>

-- 
Christoph Böhmwalder
LINBIT | Keeping the Digital World Running
DRBD HA —  Disaster Recovery — Software defined Storage