[PATCH 0/2] fix for kmemleak_erase() (Re: Q, slab, kmemleak_erase() and redzone?)

[PATCH 0/2] fix for kmemleak_erase() (Re: Q, slab, kmemleak_erase() and redzone?)

[J. R. Okajima]

Pekka Enberg:
> No, you are absolutely correct. Can you please send an updated patch to 
> Catalin that adds a comment on top of the cpu_cache_get() call that 
> explains why we need it there?

J. R. Okajima (2):
  slab, kmemleak, minor, stop calling kmemleak_erase() unconditionally
  slab, kmemleak, bugfix, pass the correct pointer to kmemleak_erase()

 mm/slab.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

[PATCH 1/2] slab, kmemleak, minor, stop calling kmemleak_erase() unconditionally

[J. R. Okajima]

When the gotten object is NULL (probably due to ENOMEM),
kmemleak_erase() is unnecessary here, It just sets NULL to where already
is NULL.
Add a condition.

Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
---
 mm/slab.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index 7dfa481..4e61449 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3109,7 +3109,8 @@ static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
 	 * per-CPU caches is leaked, we need to make sure kmemleak doesn't
 	 * treat the array pointers as a reference to the object.
 	 */
-	kmemleak_erase(&ac->entry[ac->avail]);
+	if (objp)
+		kmemleak_erase(&ac->entry[ac->avail]);
 	return objp;
 }
 
-- 
1.6.1.284.g5dc13

Re: [PATCH 1/2] slab, kmemleak, minor, stop calling kmemleak_erase() unconditionally

[Catalin Marinas]

"J. R. Okajima" <hooanon05@yahoo.co.jp> wrote:
> When the gotten object is NULL (probably due to ENOMEM),
> kmemleak_erase() is unnecessary here, It just sets NULL to where already
> is NULL.
> Add a condition.
>
> Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
> ---
>  mm/slab.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/mm/slab.c b/mm/slab.c
> index 7dfa481..4e61449 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -3109,7 +3109,8 @@ static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
>  	 * per-CPU caches is leaked, we need to make sure kmemleak doesn't
>  	 * treat the array pointers as a reference to the object.
>  	 */
> -	kmemleak_erase(&ac->entry[ac->avail]);
> +	if (objp)
> +		kmemleak_erase(&ac->entry[ac->avail]);
>  	return objp;
>  }

Acked-by: Catalin Marinas <catalin.marinas@arm.com>

-- 
Catalin

Re: [PATCH 1/2] slab, kmemleak, minor, stop calling kmemleak_erase() unconditionally

[Pekka Enberg]

Catalin Marinas wrote:
> "J. R. Okajima" <hooanon05@yahoo.co.jp> wrote:
>> When the gotten object is NULL (probably due to ENOMEM),
>> kmemleak_erase() is unnecessary here, It just sets NULL to where already
>> is NULL.
>> Add a condition.
>>
>> Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
>> ---
>>  mm/slab.c |    3 ++-
>>  1 files changed, 2 insertions(+), 1 deletions(-)
>>
>> diff --git a/mm/slab.c b/mm/slab.c
>> index 7dfa481..4e61449 100644
>> --- a/mm/slab.c
>> +++ b/mm/slab.c
>> @@ -3109,7 +3109,8 @@ static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
>>  	 * per-CPU caches is leaked, we need to make sure kmemleak doesn't
>>  	 * treat the array pointers as a reference to the object.
>>  	 */
>> -	kmemleak_erase(&ac->entry[ac->avail]);
>> +	if (objp)
>> +		kmemleak_erase(&ac->entry[ac->avail]);
>>  	return objp;
>>  }
> 
> Acked-by: Catalin Marinas <catalin.marinas@arm.com>

Applied, thanks!

[PATCH 2/2] slab, kmemleak, bugfix, pass the correct pointer to kmemleak_erase()

[J. R. Okajima]

In ____cache_alloc(), the variable 'ac' may be changed after
cache_alloc_refill() and the following kmemleak_erase() may get an
incorrect pointer.
Update 'ac' after cache_alloc_refill() unconditionally.
cf. http://marc.info/?l=linux-kernel&m=125873373124187&w=2
    and its thread.

Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Catalin Marinas <catalin.marinas@arm.com>

Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
---
 mm/slab.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/mm/slab.c b/mm/slab.c
index 4e61449..66e9047 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -3103,6 +3103,11 @@ static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
 	} else {
 		STATS_INC_ALLOCMISS(cachep);
 		objp = cache_alloc_refill(cachep, flags);
+		/*
+		 * the 'ac' may be updated by cache_alloc_refill(),
+		 * and kmemleak_erase() requires its correct value.
+		 */
+		ac = cpu_cache_get(cachep);
 	}
 	/*
 	 * To avoid a false negative, if an object that is in one of the
-- 
1.6.1.284.g5dc13

Re: [PATCH 2/2] slab, kmemleak, bugfix, pass the correct pointer to kmemleak_erase()

[Catalin Marinas]

"J. R. Okajima" <hooanon05@yahoo.co.jp> wrote:
> In ____cache_alloc(), the variable 'ac' may be changed after
> cache_alloc_refill() and the following kmemleak_erase() may get an
> incorrect pointer.
> Update 'ac' after cache_alloc_refill() unconditionally.
> cf. http://marc.info/?l=linux-kernel&m=125873373124187&w=2
>     and its thread.
>
> Cc: Pekka Enberg <penberg@cs.helsinki.fi>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
>
> Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
> ---
>  mm/slab.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
>
> diff --git a/mm/slab.c b/mm/slab.c
> index 4e61449..66e9047 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -3103,6 +3103,11 @@ static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
>  	} else {
>  		STATS_INC_ALLOCMISS(cachep);
>  		objp = cache_alloc_refill(cachep, flags);
> +		/*
> +		 * the 'ac' may be updated by cache_alloc_refill(),
> +		 * and kmemleak_erase() requires its correct value.
> +		 */
> +		ac = cpu_cache_get(cachep);
>  	}
>  	/*
>  	 * To avoid a false negative, if an object that is in one of the

Acked-by: Catalin Marinas <catalin.marinas@arm.com>

Thanks.

-- 
Catalin

Re: [PATCH 2/2] slab, kmemleak, bugfix, pass the correct pointer to kmemleak_erase()

[Pekka Enberg]

Catalin Marinas wrote:
> "J. R. Okajima" <hooanon05@yahoo.co.jp> wrote:
>> In ____cache_alloc(), the variable 'ac' may be changed after
>> cache_alloc_refill() and the following kmemleak_erase() may get an
>> incorrect pointer.
>> Update 'ac' after cache_alloc_refill() unconditionally.
>> cf. http://marc.info/?l=linux-kernel&m=125873373124187&w=2
>>     and its thread.
>>
>> Cc: Pekka Enberg <penberg@cs.helsinki.fi>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>>
>> Signed-off-by: J. R. Okajima <hooanon05@yahoo.co.jp>
>> ---
>>  mm/slab.c |    5 +++++
>>  1 files changed, 5 insertions(+), 0 deletions(-)
>>
>> diff --git a/mm/slab.c b/mm/slab.c
>> index 4e61449..66e9047 100644
>> --- a/mm/slab.c
>> +++ b/mm/slab.c
>> @@ -3103,6 +3103,11 @@ static inline void *____cache_alloc(struct kmem_cache *cachep, gfp_t flags)
>>  	} else {
>>  		STATS_INC_ALLOCMISS(cachep);
>>  		objp = cache_alloc_refill(cachep, flags);
>> +		/*
>> +		 * the 'ac' may be updated by cache_alloc_refill(),
>> +		 * and kmemleak_erase() requires its correct value.
>> +		 */
>> +		ac = cpu_cache_get(cachep);
>>  	}
>>  	/*
>>  	 * To avoid a false negative, if an object that is in one of the
> 
> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
> 
> Thanks.

Applied, thanks!

Re: [PATCH 0/2] fix for kmemleak_erase() (Re: Q, slab, kmemleak_erase() and redzone?)

[Pekka Enberg]

J. R. Okajima kirjoitti:
> Pekka Enberg:
>> No, you are absolutely correct. Can you please send an updated patch to 
>> Catalin that adds a comment on top of the cpu_cache_get() call that 
>> explains why we need it there?
> 
> J. R. Okajima (2):
>   slab, kmemleak, minor, stop calling kmemleak_erase() unconditionally
>   slab, kmemleak, bugfix, pass the correct pointer to kmemleak_erase()
> 
>  mm/slab.c |    8 +++++++-
>  1 files changed, 7 insertions(+), 1 deletions(-)

Looks good to me. I'll pick these up in slab.git. Thanks!