linux-kernel - Re: [RFC PATCH v2 1/2] lib, stackdepot: check stackdepot handle before accessing slabs.

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Date:   Thu, 2 Sep 2021 09:53:48 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Imran Khan <imran.f.khan@...cle.com>, geert@...ux-m68k.org,
        akpm@...ux-foundation.org, ryabinin.a.a@...il.com,
        glider@...gle.com, andreyknvl@...il.com, dvyukov@...gle.com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 1/2] lib, stackdepot: check stackdepot handle
 before accessing slabs.

On 9/2/21 02:01, Imran Khan wrote:
> stack_depot_save allocates slabs that will be used for storing
> objects in future.If this slab allocation fails we may get to
> a situation where space allocation for a new stack_record fails,
> causing stack_depot_save to return 0 as handle.
> If user of this handle ends up invoking stack_depot_fetch with
> this handle value, current implementation of stack_depot_fetch
> will end up using slab from wrong index.
> To avoid this check handle value at the beginning.
> 
> Signed-off-by: Imran Khan <imran.f.khan@...cle.com>
> Suggested-by: Vlastimil Babka <vbabka@...e.cz>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  lib/stackdepot.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/lib/stackdepot.c b/lib/stackdepot.c
> index 0a2e417f83cb..67439c082490 100644
> --- a/lib/stackdepot.c
> +++ b/lib/stackdepot.c
> @@ -232,6 +232,9 @@ unsigned int stack_depot_fetch(depot_stack_handle_t handle,
>  	struct stack_record *stack;
>  
>  	*entries = NULL;
> +	if (!handle)
> +		return 0;
> +
>  	if (parts.slabindex > depot_index) {
>  		WARN(1, "slab index %d out of bounds (%d) for stack id %08x\n",
>  			parts.slabindex, depot_index, handle);
>