* [PATCH] mm/kfence: Null check is added for return value of addr_to_metadata [not found] <CGME20210924121457epcas5p39266266f9cef79177f2301a6a4f7d79a@epcas5p3.samsung.com> @ 2021-09-24 12:14 ` Manjeet Pawar 2021-09-24 14:13 ` Marco Elver 0 siblings, 1 reply; 2+ messages in thread From: Manjeet Pawar @ 2021-09-24 12:14 UTC (permalink / raw) To: glider, elver, dvyukov, akpm, kasan-dev, linux-mm, linux-kernel Cc: r.thapliyal, a.sahrawat, v.narang, Manjeet Pawar This patch add null check for return value of addr_to_metadata(). currently 'meta' is geting accessed without any NULL check but it is usually checked for this function. Signed-off-by: Manjeet Pawar <manjeet.p@samsung.com> --- mm/kfence/core.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/kfence/core.c b/mm/kfence/core.c index 575c685aa642..9b953cfa7fee 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -802,6 +802,9 @@ void __kfence_free(void *addr) { struct kfence_metadata *meta = addr_to_metadata((unsigned long)addr); + if (unlikely(!meta)) + return; + /* * If the objects of the cache are SLAB_TYPESAFE_BY_RCU, defer freeing * the object, as the object page may be recycled for other-typed -- 2.17.1 ^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] mm/kfence: Null check is added for return value of addr_to_metadata 2021-09-24 12:14 ` [PATCH] mm/kfence: Null check is added for return value of addr_to_metadata Manjeet Pawar @ 2021-09-24 14:13 ` Marco Elver 0 siblings, 0 replies; 2+ messages in thread From: Marco Elver @ 2021-09-24 14:13 UTC (permalink / raw) To: Manjeet Pawar Cc: glider, dvyukov, akpm, kasan-dev, linux-mm, linux-kernel, r.thapliyal, a.sahrawat, v.narang On Fri, 24 Sept 2021 at 15:55, Manjeet Pawar <manjeet.p@samsung.com> wrote: > This patch add null check for return value of addr_to_metadata(). > currently 'meta' is geting accessed without any NULL check but it is > usually checked for this function. > > Signed-off-by: Manjeet Pawar <manjeet.p@samsung.com> Your commit message does not make sense -- what bug did you encounter? "usually checked for this function" is not a reason to add the check. Adding a check like this could also hide genuine bugs, as meta should never be NULL in __kfence_free(). If it is, we'd like to see a crash. Did you read kfence_free() in include/linux/kfence.h? It already prevents __kfence_free() being called with a non-KFENCE address. Without a more thorough explanation, Nack. Thanks, -- Marco ^ permalink raw reply [flat|nested] 2+ messages in thread
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2021-09-24 12:14 ` [PATCH] mm/kfence: Null check is added for return value of addr_to_metadata Manjeet Pawar
2021-09-24 14:13 ` Marco Elver
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