As the possible failure of the kmalloc_slab,
it should be better to check it.
Signed-off-by: Ren Yu <[email protected]>
---
mm/slab.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/mm/slab.c b/mm/slab.c
index f8cd00f4ba13..72135e555827 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2064,6 +2064,8 @@ int __kmem_cache_create(struct kmem_cache *cachep, slab_flags_t flags)
if (OFF_SLAB(cachep)) {
cachep->freelist_cache =
kmalloc_slab(cachep->freelist_size, 0u);
+ if (unlikely(ZERO_OR_NULL_PTR(cachep->freelist_cache)))
+ return cachep->freelist_cache;
}
err = setup_cpu_cache(cachep, gfp);
--
2.11.0
Hi Ren,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on akpm-mm/mm-everything]
url: https://github.com/intel-lab-lkp/linux/commits/Ren-Yu/mm-check-the-function-kmalloc_slab-return-value/20220613-182849
base: https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-everything
config: um-i386_defconfig (https://download.01.org/0day-ci/archive/20220613/[email protected]/config)
compiler: gcc-11 (Debian 11.3.0-3) 11.3.0
reproduce (this is a W=1 build):
# https://github.com/intel-lab-lkp/linux/commit/5ba2024be9e85177c986e9078e903798cac72f74
git remote add linux-review https://github.com/intel-lab-lkp/linux
git fetch --no-tags linux-review Ren-Yu/mm-check-the-function-kmalloc_slab-return-value/20220613-182849
git checkout 5ba2024be9e85177c986e9078e903798cac72f74
# save the config file
mkdir build_dir && cp config build_dir/.config
make W=1 O=build_dir ARCH=um SUBARCH=i386 SHELL=/bin/bash
If you fix the issue, kindly add following tag where applicable
Reported-by: kernel test robot <[email protected]>
All warnings (new ones prefixed by >>):
mm/slab.c: In function '__kmem_cache_create':
>> mm/slab.c:2068:38: warning: returning 'struct kmem_cache *' from a function with return type 'int' makes integer from pointer without a cast [-Wint-conversion]
2068 | return cachep->freelist_cache;
| ~~~~~~^~~~~~~~~~~~~~~~
vim +2068 mm/slab.c
2063
2064 if (OFF_SLAB(cachep)) {
2065 cachep->freelist_cache =
2066 kmalloc_slab(cachep->freelist_size, 0u);
2067 if (unlikely(ZERO_OR_NULL_PTR(cachep->freelist_cache)))
> 2068 return cachep->freelist_cache;
2069 }
2070
2071 err = setup_cpu_cache(cachep, gfp);
2072 if (err) {
2073 __kmem_cache_release(cachep);
2074 return err;
2075 }
2076
2077 return 0;
2078 }
2079
--
0-DAY CI Kernel Test Service
https://01.org/lkp
On 6/14/22 10:39, Ren Yu wrote:
> As the possible failure of the kmalloc_slab,
> it should be better to check it.
AFAIK failure is not possible, kmalloc_slab() is not an allocation function,
it just returns a member of kmalloc_caches array, which is initialized
elsewhere and shouldn't contain NULLs. So the patch seems unnecessary to me.
> Signed-off-by: Ren Yu <[email protected]>
> Reported-by: kernel test robot <[email protected]>
> ---
> v2:
> - fix build waring integer from pointer without a cast
> ---
> ---
> mm/slab.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/mm/slab.c b/mm/slab.c
> index f8cd00f4ba13..72135e555827 100644
> --- a/mm/slab.c
> +++ b/mm/slab.c
> @@ -2064,6 +2064,8 @@ int __kmem_cache_create(struct kmem_cache *cachep, slab_flags_t flags)
> if (OFF_SLAB(cachep)) {
> cachep->freelist_cache =
> kmalloc_slab(cachep->freelist_size, 0u);
> + if (unlikely(ZERO_OR_NULL_PTR(cachep->freelist_cache)))
The usual way is "if (!cachep->freelist_cache)". Not sure why check for ZERO.
> + return cachep->freelist_cache;
So in case of NULL this would return NULL, thus 0, but __kmem_cache_create()
return 0 on success, so it's wrong. You would have to return e.g. -ENOMEM.
> }
>
> err = setup_cpu_cache(cachep, gfp);
As the possible failure of the kmalloc_slab,
it should be better to check it.
Signed-off-by: Ren Yu <[email protected]>
Reported-by: kernel test robot <[email protected]>
---
v2:
- fix build waring integer from pointer without a cast
---
---
mm/slab.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/mm/slab.c b/mm/slab.c
index f8cd00f4ba13..72135e555827 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2064,6 +2064,8 @@ int __kmem_cache_create(struct kmem_cache *cachep, slab_flags_t flags)
if (OFF_SLAB(cachep)) {
cachep->freelist_cache =
kmalloc_slab(cachep->freelist_size, 0u);
+ if (unlikely(ZERO_OR_NULL_PTR(cachep->freelist_cache)))
+ return cachep->freelist_cache;
}
err = setup_cpu_cache(cachep, gfp);
--
2.11.0
在 2022年06月14日 16:48, Vlastimil Babka 写道:
> On 6/14/22 10:39, Ren Yu wrote:
>> As the possible failure of the kmalloc_slab,
>> it should be better to check it.
> AFAIK failure is not possible, kmalloc_slab() is not an allocation function,
> it just returns a member of kmalloc_caches array, which is initialized
> elsewhere and shouldn't contain NULLs. So the patch seems unnecessary to me.
>
>> Signed-off-by: Ren Yu <[email protected]>
>> Reported-by: kernel test robot <[email protected]>
>> ---
>> v2:
>> - fix build waring integer from pointer without a cast
>> ---
>> ---
>> mm/slab.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/mm/slab.c b/mm/slab.c
>> index f8cd00f4ba13..72135e555827 100644
>> --- a/mm/slab.c
>> +++ b/mm/slab.c
>> @@ -2064,6 +2064,8 @@ int __kmem_cache_create(struct kmem_cache *cachep, slab_flags_t flags)
>> if (OFF_SLAB(cachep)) {
>> cachep->freelist_cache =
>> kmalloc_slab(cachep->freelist_size, 0u);
>> + if (unlikely(ZERO_OR_NULL_PTR(cachep->freelist_cache)))
> The usual way is "if (!cachep->freelist_cache)". Not sure why check for ZERO.
>
>> + return cachep->freelist_cache;
> So in case of NULL this would return NULL, thus 0, but __kmem_cache_create()
> return 0 on success, so it's wrong. You would have to return e.g. -ENOMEM.
Thanks for the advice ,I'll be re-patching
>
>> }
>>
>> err = setup_cpu_cache(cachep, gfp);
>
As the possible failure of the kmalloc_slab,
it should be better to check it.
Signed-off-by: Ren Yu <[email protected]>
Reported-by: kernel test robot <[email protected]>
---
v2:
- change return value of error path to '-ENOMEM'
- not check for zero
---
mm/slab.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/mm/slab.c b/mm/slab.c
index f8cd00f4ba13..eb3fb042f4f4 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2064,6 +2064,8 @@ int __kmem_cache_create(struct kmem_cache *cachep, slab_flags_t flags)
if (OFF_SLAB(cachep)) {
cachep->freelist_cache =
kmalloc_slab(cachep->freelist_size, 0u);
+ if (!cachep->freelist_cache)
+ return -ENOMEM;
}
err = setup_cpu_cache(cachep, gfp);
--
2.11.0
On 6/14/22 11:26, tury wrote:
>
>
> 在 2022年06月14日 16:48, Vlastimil Babka 写道:
>> On 6/14/22 10:39, Ren Yu wrote:
>>> As the possible failure of the kmalloc_slab,
>>> it should be better to check it.
>> AFAIK failure is not possible, kmalloc_slab() is not an allocation function,
>> it just returns a member of kmalloc_caches array, which is initialized
>> elsewhere and shouldn't contain NULLs. So the patch seems unnecessary to me.
>>
>>> Signed-off-by: Ren Yu <[email protected]>
>>> Reported-by: kernel test robot <[email protected]>
>>> ---
>>> v2:
>>> - fix build waring integer from pointer without a cast
>>> ---
>>> ---
>>> mm/slab.c | 2 ++
>>> 1 file changed, 2 insertions(+)
>>>
>>> diff --git a/mm/slab.c b/mm/slab.c
>>> index f8cd00f4ba13..72135e555827 100644
>>> --- a/mm/slab.c
>>> +++ b/mm/slab.c
>>> @@ -2064,6 +2064,8 @@ int __kmem_cache_create(struct kmem_cache *cachep,
>>> slab_flags_t flags)
>>> if (OFF_SLAB(cachep)) {
>>> cachep->freelist_cache =
>>> kmalloc_slab(cachep->freelist_size, 0u);
>>> + if (unlikely(ZERO_OR_NULL_PTR(cachep->freelist_cache)))
>> The usual way is "if (!cachep->freelist_cache)". Not sure why check for ZERO.
>>
>>> + return cachep->freelist_cache;
>> So in case of NULL this would return NULL, thus 0, but __kmem_cache_create()
>> return 0 on success, so it's wrong. You would have to return e.g. -ENOMEM.
> Thanks for the advice ,I'll be re-patching
However that was meant just for your information/learning, the patch is
still unecessary as I wrote above, so I will not merge it so we don't
complicate the code needlessly.
>>
>>> }
>>> err = setup_cpu_cache(cachep, gfp);
>>
>