diff mbox series

[v2,01/16] slab: Remove __malloc attribute from realloc functions

Message ID 20220923202822.2667581-2-keescook@chromium.org (mailing list archive)
State New
Headers show
Series slab: Introduce kmalloc_size_roundup() | expand

Commit Message

Kees Cook Sept. 23, 2022, 8:28 p.m. UTC
The __malloc attribute should not be applied to "realloc" functions, as
the returned pointer may alias the storage of the prior pointer. Instead
of splitting __malloc from __alloc_size, which would be a huge amount of
churn, just create __realloc_size for the few cases where it is needed.

Additionally removes the conditional test for __alloc_size__, which is
always defined now.

Cc: Christoph Lameter <cl@linux.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Marco Elver <elver@google.com>
Cc: linux-mm@kvack.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/compiler_types.h | 13 +++++--------
 include/linux/slab.h           | 12 ++++++------
 mm/slab_common.c               |  4 ++--
 3 files changed, 13 insertions(+), 16 deletions(-)

Comments

Geert Uytterhoeven Sept. 28, 2022, 7:26 a.m. UTC | #1
Hi Kees,

On Fri, Sep 23, 2022 at 10:35 PM Kees Cook <keescook@chromium.org> wrote:
> The __malloc attribute should not be applied to "realloc" functions, as
> the returned pointer may alias the storage of the prior pointer. Instead
> of splitting __malloc from __alloc_size, which would be a huge amount of
> churn, just create __realloc_size for the few cases where it is needed.
>
> Additionally removes the conditional test for __alloc_size__, which is
> always defined now.
>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: Pekka Enberg <penberg@kernel.org>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Roman Gushchin <roman.gushchin@linux.dev>
> Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> Cc: Marco Elver <elver@google.com>
> Cc: linux-mm@kvack.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Thanks for your patch, which is now commit 63caa04ec60583b1 ("slab:
Remove __malloc attribute from realloc functions") in next-20220927.

Noreply@ellerman.id.au reported all gcc8-based builds to fail
(e.g. [1], more at [2]):

    In file included from <command-line>:
    ./include/linux/percpu.h: In function ‘__alloc_reserved_percpu’:
    ././include/linux/compiler_types.h:279:30: error: expected
declaration specifiers before ‘__alloc_size__’
     #define __alloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) __malloc
                                  ^~~~~~~~~~~~~~
    ./include/linux/percpu.h:120:74: note: in expansion of macro ‘__alloc_size’
    [...]

It's building fine with e.g. gcc-9 (which is my usual m68k cross-compiler).
Reverting this commit on next-20220927 fixes the issue.

[1] http://kisskb.ellerman.id.au/kisskb/buildresult/14803908/
[2] http://kisskb.ellerman.id.au/kisskb/head/1bd8b75fe6adeaa89d02968bdd811ffe708cf839/



> ---
>  include/linux/compiler_types.h | 13 +++++--------
>  include/linux/slab.h           | 12 ++++++------
>  mm/slab_common.c               |  4 ++--
>  3 files changed, 13 insertions(+), 16 deletions(-)
>
> diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
> index 4f2a819fd60a..f141a6f6b9f6 100644
> --- a/include/linux/compiler_types.h
> +++ b/include/linux/compiler_types.h
> @@ -271,15 +271,12 @@ struct ftrace_likely_data {
>
>  /*
>   * Any place that could be marked with the "alloc_size" attribute is also
> - * a place to be marked with the "malloc" attribute. Do this as part of the
> - * __alloc_size macro to avoid redundant attributes and to avoid missing a
> - * __malloc marking.
> + * a place to be marked with the "malloc" attribute, except those that may
> + * be performing a _reallocation_, as that may alias the existing pointer.
> + * For these, use __realloc_size().
>   */
> -#ifdef __alloc_size__
> -# define __alloc_size(x, ...)  __alloc_size__(x, ## __VA_ARGS__) __malloc
> -#else
> -# define __alloc_size(x, ...)  __malloc
> -#endif
> +#define __alloc_size(x, ...)   __alloc_size__(x, ## __VA_ARGS__) __malloc
> +#define __realloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__)
>
>  #ifndef asm_volatile_goto
>  #define asm_volatile_goto(x...) asm goto(x)
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 0fefdf528e0d..41bd036e7551 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -184,7 +184,7 @@ int kmem_cache_shrink(struct kmem_cache *s);
>  /*
>   * Common kmalloc functions provided by all allocators
>   */
> -void * __must_check krealloc(const void *objp, size_t new_size, gfp_t flags) __alloc_size(2);
> +void * __must_check krealloc(const void *objp, size_t new_size, gfp_t flags) __realloc_size(2);
>  void kfree(const void *objp);
>  void kfree_sensitive(const void *objp);
>  size_t __ksize(const void *objp);
> @@ -647,10 +647,10 @@ static inline __alloc_size(1, 2) void *kmalloc_array(size_t n, size_t size, gfp_
>   * @new_size: new size of a single member of the array
>   * @flags: the type of memory to allocate (see kmalloc)
>   */
> -static inline __alloc_size(2, 3) void * __must_check krealloc_array(void *p,
> -                                                                   size_t new_n,
> -                                                                   size_t new_size,
> -                                                                   gfp_t flags)
> +static inline __realloc_size(2, 3) void * __must_check krealloc_array(void *p,
> +                                                                     size_t new_n,
> +                                                                     size_t new_size,
> +                                                                     gfp_t flags)
>  {
>         size_t bytes;
>
> @@ -774,7 +774,7 @@ static inline __alloc_size(1, 2) void *kvcalloc(size_t n, size_t size, gfp_t fla
>  }
>
>  extern void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags)
> -                     __alloc_size(3);
> +                     __realloc_size(3);
>  extern void kvfree(const void *addr);
>  extern void kvfree_sensitive(const void *addr, size_t len);
>
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 17996649cfe3..457671ace7eb 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -1134,8 +1134,8 @@ module_init(slab_proc_init);
>
>  #endif /* CONFIG_SLAB || CONFIG_SLUB_DEBUG */
>
> -static __always_inline void *__do_krealloc(const void *p, size_t new_size,
> -                                          gfp_t flags)
> +static __always_inline __realloc_size(2) void *
> +__do_krealloc(const void *p, size_t new_size, gfp_t flags)
>  {
>         void *ret;
>         size_t ks;
> --
> 2.34.1
>


--
Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
Vlastimil Babka Sept. 28, 2022, 4:27 p.m. UTC | #2
On 9/28/22 09:26, Geert Uytterhoeven wrote:
> Hi Kees,
> 
> On Fri, Sep 23, 2022 at 10:35 PM Kees Cook <keescook@chromium.org> wrote:
>> The __malloc attribute should not be applied to "realloc" functions, as
>> the returned pointer may alias the storage of the prior pointer. Instead
>> of splitting __malloc from __alloc_size, which would be a huge amount of
>> churn, just create __realloc_size for the few cases where it is needed.
>>
>> Additionally removes the conditional test for __alloc_size__, which is
>> always defined now.
>>
>> Cc: Christoph Lameter <cl@linux.com>
>> Cc: Pekka Enberg <penberg@kernel.org>
>> Cc: David Rientjes <rientjes@google.com>
>> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>> Cc: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Vlastimil Babka <vbabka@suse.cz>
>> Cc: Roman Gushchin <roman.gushchin@linux.dev>
>> Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
>> Cc: Marco Elver <elver@google.com>
>> Cc: linux-mm@kvack.org
>> Signed-off-by: Kees Cook <keescook@chromium.org>
> 
> Thanks for your patch, which is now commit 63caa04ec60583b1 ("slab:
> Remove __malloc attribute from realloc functions") in next-20220927.
> 
> Noreply@ellerman.id.au reported all gcc8-based builds to fail
> (e.g. [1], more at [2]):
> 
>      In file included from <command-line>:
>      ./include/linux/percpu.h: In function ‘__alloc_reserved_percpu’:
>      ././include/linux/compiler_types.h:279:30: error: expected
> declaration specifiers before ‘__alloc_size__’
>       #define __alloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) __malloc
>                                    ^~~~~~~~~~~~~~
>      ./include/linux/percpu.h:120:74: note: in expansion of macro ‘__alloc_size’
>      [...]
> 
> It's building fine with e.g. gcc-9 (which is my usual m68k cross-compiler).
> Reverting this commit on next-20220927 fixes the issue.

So IIUC it was wrong to remove the #ifdefs?

> [1] http://kisskb.ellerman.id.au/kisskb/buildresult/14803908/
> [2] http://kisskb.ellerman.id.au/kisskb/head/1bd8b75fe6adeaa89d02968bdd811ffe708cf839/
> 
> 
> 
>> ---
>>   include/linux/compiler_types.h | 13 +++++--------
>>   include/linux/slab.h           | 12 ++++++------
>>   mm/slab_common.c               |  4 ++--
>>   3 files changed, 13 insertions(+), 16 deletions(-)
>>
>> diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
>> index 4f2a819fd60a..f141a6f6b9f6 100644
>> --- a/include/linux/compiler_types.h
>> +++ b/include/linux/compiler_types.h
>> @@ -271,15 +271,12 @@ struct ftrace_likely_data {
>>
>>   /*
>>    * Any place that could be marked with the "alloc_size" attribute is also
>> - * a place to be marked with the "malloc" attribute. Do this as part of the
>> - * __alloc_size macro to avoid redundant attributes and to avoid missing a
>> - * __malloc marking.
>> + * a place to be marked with the "malloc" attribute, except those that may
>> + * be performing a _reallocation_, as that may alias the existing pointer.
>> + * For these, use __realloc_size().
>>    */
>> -#ifdef __alloc_size__
>> -# define __alloc_size(x, ...)  __alloc_size__(x, ## __VA_ARGS__) __malloc
>> -#else
>> -# define __alloc_size(x, ...)  __malloc
>> -#endif
>> +#define __alloc_size(x, ...)   __alloc_size__(x, ## __VA_ARGS__) __malloc
>> +#define __realloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__)
>>
>>   #ifndef asm_volatile_goto
>>   #define asm_volatile_goto(x...) asm goto(x)
>> diff --git a/include/linux/slab.h b/include/linux/slab.h
>> index 0fefdf528e0d..41bd036e7551 100644
>> --- a/include/linux/slab.h
>> +++ b/include/linux/slab.h
>> @@ -184,7 +184,7 @@ int kmem_cache_shrink(struct kmem_cache *s);
>>   /*
>>    * Common kmalloc functions provided by all allocators
>>    */
>> -void * __must_check krealloc(const void *objp, size_t new_size, gfp_t flags) __alloc_size(2);
>> +void * __must_check krealloc(const void *objp, size_t new_size, gfp_t flags) __realloc_size(2);
>>   void kfree(const void *objp);
>>   void kfree_sensitive(const void *objp);
>>   size_t __ksize(const void *objp);
>> @@ -647,10 +647,10 @@ static inline __alloc_size(1, 2) void *kmalloc_array(size_t n, size_t size, gfp_
>>    * @new_size: new size of a single member of the array
>>    * @flags: the type of memory to allocate (see kmalloc)
>>    */
>> -static inline __alloc_size(2, 3) void * __must_check krealloc_array(void *p,
>> -                                                                   size_t new_n,
>> -                                                                   size_t new_size,
>> -                                                                   gfp_t flags)
>> +static inline __realloc_size(2, 3) void * __must_check krealloc_array(void *p,
>> +                                                                     size_t new_n,
>> +                                                                     size_t new_size,
>> +                                                                     gfp_t flags)
>>   {
>>          size_t bytes;
>>
>> @@ -774,7 +774,7 @@ static inline __alloc_size(1, 2) void *kvcalloc(size_t n, size_t size, gfp_t fla
>>   }
>>
>>   extern void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags)
>> -                     __alloc_size(3);
>> +                     __realloc_size(3);
>>   extern void kvfree(const void *addr);
>>   extern void kvfree_sensitive(const void *addr, size_t len);
>>
>> diff --git a/mm/slab_common.c b/mm/slab_common.c
>> index 17996649cfe3..457671ace7eb 100644
>> --- a/mm/slab_common.c
>> +++ b/mm/slab_common.c
>> @@ -1134,8 +1134,8 @@ module_init(slab_proc_init);
>>
>>   #endif /* CONFIG_SLAB || CONFIG_SLUB_DEBUG */
>>
>> -static __always_inline void *__do_krealloc(const void *p, size_t new_size,
>> -                                          gfp_t flags)
>> +static __always_inline __realloc_size(2) void *
>> +__do_krealloc(const void *p, size_t new_size, gfp_t flags)
>>   {
>>          void *ret;
>>          size_t ks;
>> --
>> 2.34.1
>>
> 
> 
> --
> Gr{oetje,eeting}s,
> 
>                          Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                  -- Linus Torvalds
Kees Cook Sept. 28, 2022, 5:13 p.m. UTC | #3
On Wed, Sep 28, 2022 at 09:26:15AM +0200, Geert Uytterhoeven wrote:
> Hi Kees,
> 
> On Fri, Sep 23, 2022 at 10:35 PM Kees Cook <keescook@chromium.org> wrote:
> > The __malloc attribute should not be applied to "realloc" functions, as
> > the returned pointer may alias the storage of the prior pointer. Instead
> > of splitting __malloc from __alloc_size, which would be a huge amount of
> > churn, just create __realloc_size for the few cases where it is needed.
> >
> > Additionally removes the conditional test for __alloc_size__, which is
> > always defined now.
> >
> > Cc: Christoph Lameter <cl@linux.com>
> > Cc: Pekka Enberg <penberg@kernel.org>
> > Cc: David Rientjes <rientjes@google.com>
> > Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Vlastimil Babka <vbabka@suse.cz>
> > Cc: Roman Gushchin <roman.gushchin@linux.dev>
> > Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> > Cc: Marco Elver <elver@google.com>
> > Cc: linux-mm@kvack.org
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> 
> Thanks for your patch, which is now commit 63caa04ec60583b1 ("slab:
> Remove __malloc attribute from realloc functions") in next-20220927.
> 
> Noreply@ellerman.id.au reported all gcc8-based builds to fail
> (e.g. [1], more at [2]):
> 
>     In file included from <command-line>:
>     ./include/linux/percpu.h: In function ‘__alloc_reserved_percpu’:
>     ././include/linux/compiler_types.h:279:30: error: expected
> declaration specifiers before ‘__alloc_size__’
>      #define __alloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) __malloc
>                                   ^~~~~~~~~~~~~~
>     ./include/linux/percpu.h:120:74: note: in expansion of macro ‘__alloc_size’
>     [...]
> 
> It's building fine with e.g. gcc-9 (which is my usual m68k cross-compiler).
> Reverting this commit on next-20220927 fixes the issue.
> 
> [1] http://kisskb.ellerman.id.au/kisskb/buildresult/14803908/
> [2] http://kisskb.ellerman.id.au/kisskb/head/1bd8b75fe6adeaa89d02968bdd811ffe708cf839/

Eek! Thanks for letting me know. I'm confused about this --
__alloc_size__ wasn't optional in compiler_attributes.h -- but obviously
I broke something! I'll go figure this out.

-Kees
Vlastimil Babka Sept. 28, 2022, 9:39 p.m. UTC | #4
On 9/28/22 19:13, Kees Cook wrote:
> On Wed, Sep 28, 2022 at 09:26:15AM +0200, Geert Uytterhoeven wrote:
>> Hi Kees,
>>
>> On Fri, Sep 23, 2022 at 10:35 PM Kees Cook <keescook@chromium.org> wrote:
>>> The __malloc attribute should not be applied to "realloc" functions, as
>>> the returned pointer may alias the storage of the prior pointer. Instead
>>> of splitting __malloc from __alloc_size, which would be a huge amount of
>>> churn, just create __realloc_size for the few cases where it is needed.
>>>
>>> Additionally removes the conditional test for __alloc_size__, which is
>>> always defined now.
>>>
>>> Cc: Christoph Lameter <cl@linux.com>
>>> Cc: Pekka Enberg <penberg@kernel.org>
>>> Cc: David Rientjes <rientjes@google.com>
>>> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>>> Cc: Andrew Morton <akpm@linux-foundation.org>
>>> Cc: Vlastimil Babka <vbabka@suse.cz>
>>> Cc: Roman Gushchin <roman.gushchin@linux.dev>
>>> Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
>>> Cc: Marco Elver <elver@google.com>
>>> Cc: linux-mm@kvack.org
>>> Signed-off-by: Kees Cook <keescook@chromium.org>
>>
>> Thanks for your patch, which is now commit 63caa04ec60583b1 ("slab:
>> Remove __malloc attribute from realloc functions") in next-20220927.
>>
>> Noreply@ellerman.id.au reported all gcc8-based builds to fail
>> (e.g. [1], more at [2]):
>>
>>      In file included from <command-line>:
>>      ./include/linux/percpu.h: In function ‘__alloc_reserved_percpu’:
>>      ././include/linux/compiler_types.h:279:30: error: expected
>> declaration specifiers before ‘__alloc_size__’
>>       #define __alloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) __malloc
>>                                    ^~~~~~~~~~~~~~
>>      ./include/linux/percpu.h:120:74: note: in expansion of macro ‘__alloc_size’
>>      [...]
>>
>> It's building fine with e.g. gcc-9 (which is my usual m68k cross-compiler).
>> Reverting this commit on next-20220927 fixes the issue.
>>
>> [1] http://kisskb.ellerman.id.au/kisskb/buildresult/14803908/
>> [2] http://kisskb.ellerman.id.au/kisskb/head/1bd8b75fe6adeaa89d02968bdd811ffe708cf839/
> 
> Eek! Thanks for letting me know. I'm confused about this --
> __alloc_size__ wasn't optional in compiler_attributes.h -- but obviously
> I broke something! I'll go figure this out.

Even in latest next I can see at the end of include/linux/compiler-gcc.h

/*
  * Prior to 9.1, -Wno-alloc-size-larger-than (and therefore the "alloc_size"
  * attribute) do not work, and must be disabled.
  */
#if GCC_VERSION < 90100
#undef __alloc_size__
#endif



> -Kees
>
Michael Ellerman Sept. 29, 2022, 8:36 a.m. UTC | #5
Kees Cook <keescook@chromium.org> writes:
> On Wed, Sep 28, 2022 at 09:26:15AM +0200, Geert Uytterhoeven wrote:
>> On Fri, Sep 23, 2022 at 10:35 PM Kees Cook <keescook@chromium.org> wrote:
>> > The __malloc attribute should not be applied to "realloc" functions, as
>> > the returned pointer may alias the storage of the prior pointer. Instead
>> > of splitting __malloc from __alloc_size, which would be a huge amount of
>> > churn, just create __realloc_size for the few cases where it is needed.
>> >
>> > Additionally removes the conditional test for __alloc_size__, which is
>> > always defined now.
>> >
>> > Cc: Christoph Lameter <cl@linux.com>
>> > Cc: Pekka Enberg <penberg@kernel.org>
>> > Cc: David Rientjes <rientjes@google.com>
>> > Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
>> > Cc: Andrew Morton <akpm@linux-foundation.org>
>> > Cc: Vlastimil Babka <vbabka@suse.cz>
>> > Cc: Roman Gushchin <roman.gushchin@linux.dev>
>> > Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
>> > Cc: Marco Elver <elver@google.com>
>> > Cc: linux-mm@kvack.org
>> > Signed-off-by: Kees Cook <keescook@chromium.org>
>> 
>> Thanks for your patch, which is now commit 63caa04ec60583b1 ("slab:
>> Remove __malloc attribute from realloc functions") in next-20220927.
>> 
>> Noreply@ellerman.id.au reported all gcc8-based builds to fail
>> (e.g. [1], more at [2]):
>> 
>>     In file included from <command-line>:
>>     ./include/linux/percpu.h: In function ‘__alloc_reserved_percpu’:
>>     ././include/linux/compiler_types.h:279:30: error: expected
>> declaration specifiers before ‘__alloc_size__’
>>      #define __alloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) __malloc
>>                                   ^~~~~~~~~~~~~~
>>     ./include/linux/percpu.h:120:74: note: in expansion of macro ‘__alloc_size’
>>     [...]
>> 
>> It's building fine with e.g. gcc-9 (which is my usual m68k cross-compiler).
>> Reverting this commit on next-20220927 fixes the issue.
>> 
>> [1] http://kisskb.ellerman.id.au/kisskb/buildresult/14803908/
>> [2] http://kisskb.ellerman.id.au/kisskb/head/1bd8b75fe6adeaa89d02968bdd811ffe708cf839/
>
> Eek! Thanks for letting me know. I'm confused about this --
> __alloc_size__ wasn't optional in compiler_attributes.h -- but obviously
> I broke something! I'll go figure this out.

This fixes it for me.

cheers

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index f141a6f6b9f6..0717534f8364 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -275,8 +275,13 @@ struct ftrace_likely_data {
  * be performing a _reallocation_, as that may alias the existing pointer.
  * For these, use __realloc_size().
  */
-#define __alloc_size(x, ...)	__alloc_size__(x, ## __VA_ARGS__) __malloc
-#define __realloc_size(x, ...)	__alloc_size__(x, ## __VA_ARGS__)
+#ifdef __alloc_size__
+# define __alloc_size(x, ...)	__alloc_size__(x, ## __VA_ARGS__) __malloc
+# define __realloc_size(x, ...)	__alloc_size__(x, ## __VA_ARGS__)
+#else
+# define __alloc_size(x, ...)	__malloc
+# define __realloc_size(x, ...)
+#endif
 
 #ifndef asm_volatile_goto
 #define asm_volatile_goto(x...) asm goto(x)
Geert Uytterhoeven Sept. 29, 2022, 9 a.m. UTC | #6
Hi Michael,

On Thu, Sep 29, 2022 at 10:36 AM Michael Ellerman <mpe@ellerman.id.au> wrote:
> Kees Cook <keescook@chromium.org> writes:
> > On Wed, Sep 28, 2022 at 09:26:15AM +0200, Geert Uytterhoeven wrote:
> >> On Fri, Sep 23, 2022 at 10:35 PM Kees Cook <keescook@chromium.org> wrote:
> >> > The __malloc attribute should not be applied to "realloc" functions, as
> >> > the returned pointer may alias the storage of the prior pointer. Instead
> >> > of splitting __malloc from __alloc_size, which would be a huge amount of
> >> > churn, just create __realloc_size for the few cases where it is needed.
> >> >
> >> > Additionally removes the conditional test for __alloc_size__, which is
> >> > always defined now.
> >> >
> >> > Cc: Christoph Lameter <cl@linux.com>
> >> > Cc: Pekka Enberg <penberg@kernel.org>
> >> > Cc: David Rientjes <rientjes@google.com>
> >> > Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> >> > Cc: Andrew Morton <akpm@linux-foundation.org>
> >> > Cc: Vlastimil Babka <vbabka@suse.cz>
> >> > Cc: Roman Gushchin <roman.gushchin@linux.dev>
> >> > Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> >> > Cc: Marco Elver <elver@google.com>
> >> > Cc: linux-mm@kvack.org
> >> > Signed-off-by: Kees Cook <keescook@chromium.org>
> >>
> >> Thanks for your patch, which is now commit 63caa04ec60583b1 ("slab:
> >> Remove __malloc attribute from realloc functions") in next-20220927.
> >>
> >> Noreply@ellerman.id.au reported all gcc8-based builds to fail
> >> (e.g. [1], more at [2]):
> >>
> >>     In file included from <command-line>:
> >>     ./include/linux/percpu.h: In function ‘__alloc_reserved_percpu’:
> >>     ././include/linux/compiler_types.h:279:30: error: expected
> >> declaration specifiers before ‘__alloc_size__’
> >>      #define __alloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__) __malloc
> >>                                   ^~~~~~~~~~~~~~
> >>     ./include/linux/percpu.h:120:74: note: in expansion of macro ‘__alloc_size’
> >>     [...]
> >>
> >> It's building fine with e.g. gcc-9 (which is my usual m68k cross-compiler).
> >> Reverting this commit on next-20220927 fixes the issue.
> >>
> >> [1] http://kisskb.ellerman.id.au/kisskb/buildresult/14803908/
> >> [2] http://kisskb.ellerman.id.au/kisskb/head/1bd8b75fe6adeaa89d02968bdd811ffe708cf839/
> >
> > Eek! Thanks for letting me know. I'm confused about this --
> > __alloc_size__ wasn't optional in compiler_attributes.h -- but obviously
> > I broke something! I'll go figure this out.
>
> This fixes it for me.

Kees submitted a similar patch 20 minutes before:
https://lore.kernel.org/all/20220929081642.1932200-1-keescook@chromium.org

> --- a/include/linux/compiler_types.h
> +++ b/include/linux/compiler_types.h
> @@ -275,8 +275,13 @@ struct ftrace_likely_data {
>   * be performing a _reallocation_, as that may alias the existing pointer.
>   * For these, use __realloc_size().
>   */
> -#define __alloc_size(x, ...)   __alloc_size__(x, ## __VA_ARGS__) __malloc
> -#define __realloc_size(x, ...) __alloc_size__(x, ## __VA_ARGS__)
> +#ifdef __alloc_size__
> +# define __alloc_size(x, ...)  __alloc_size__(x, ## __VA_ARGS__) __malloc
> +# define __realloc_size(x, ...)        __alloc_size__(x, ## __VA_ARGS__)
> +#else
> +# define __alloc_size(x, ...)  __malloc
> +# define __realloc_size(x, ...)
> +#endif
>
>  #ifndef asm_volatile_goto
>  #define asm_volatile_goto(x...) asm goto(x)


Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
Hyeonggon Yoo Oct. 1, 2022, 4:09 p.m. UTC | #7
On Fri, Sep 23, 2022 at 01:28:07PM -0700, Kees Cook wrote:
> The __malloc attribute should not be applied to "realloc" functions, as
> the returned pointer may alias the storage of the prior pointer. Instead
> of splitting __malloc from __alloc_size, which would be a huge amount of
> churn, just create __realloc_size for the few cases where it is needed.
> 
> Additionally removes the conditional test for __alloc_size__, which is
> always defined now.
> 
> Cc: Christoph Lameter <cl@linux.com>
> Cc: Pekka Enberg <penberg@kernel.org>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Roman Gushchin <roman.gushchin@linux.dev>
> Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
> Cc: Marco Elver <elver@google.com>
> Cc: linux-mm@kvack.org
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  include/linux/compiler_types.h | 13 +++++--------
>  include/linux/slab.h           | 12 ++++++------
>  mm/slab_common.c               |  4 ++--
>  3 files changed, 13 insertions(+), 16 deletions(-)
> 
> diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
> index 4f2a819fd60a..f141a6f6b9f6 100644
> --- a/include/linux/compiler_types.h
> +++ b/include/linux/compiler_types.h
> @@ -271,15 +271,12 @@ struct ftrace_likely_data {
>  
>  /*
>   * Any place that could be marked with the "alloc_size" attribute is also
> - * a place to be marked with the "malloc" attribute. Do this as part of the
> - * __alloc_size macro to avoid redundant attributes and to avoid missing a
> - * __malloc marking.
> + * a place to be marked with the "malloc" attribute, except those that may
> + * be performing a _reallocation_, as that may alias the existing pointer.
> + * For these, use __realloc_size().
>   */
> -#ifdef __alloc_size__
> -# define __alloc_size(x, ...)	__alloc_size__(x, ## __VA_ARGS__) __malloc
> -#else
> -# define __alloc_size(x, ...)	__malloc
> -#endif
> +#define __alloc_size(x, ...)	__alloc_size__(x, ## __VA_ARGS__) __malloc
> +#define __realloc_size(x, ...)	__alloc_size__(x, ## __VA_ARGS__)
>  
>  #ifndef asm_volatile_goto
>  #define asm_volatile_goto(x...) asm goto(x)
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 0fefdf528e0d..41bd036e7551 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -184,7 +184,7 @@ int kmem_cache_shrink(struct kmem_cache *s);
>  /*
>   * Common kmalloc functions provided by all allocators
>   */
> -void * __must_check krealloc(const void *objp, size_t new_size, gfp_t flags) __alloc_size(2);
> +void * __must_check krealloc(const void *objp, size_t new_size, gfp_t flags) __realloc_size(2);
>  void kfree(const void *objp);
>  void kfree_sensitive(const void *objp);
>  size_t __ksize(const void *objp);
> @@ -647,10 +647,10 @@ static inline __alloc_size(1, 2) void *kmalloc_array(size_t n, size_t size, gfp_
>   * @new_size: new size of a single member of the array
>   * @flags: the type of memory to allocate (see kmalloc)
>   */
> -static inline __alloc_size(2, 3) void * __must_check krealloc_array(void *p,
> -								    size_t new_n,
> -								    size_t new_size,
> -								    gfp_t flags)
> +static inline __realloc_size(2, 3) void * __must_check krealloc_array(void *p,
> +								      size_t new_n,
> +								      size_t new_size,
> +								      gfp_t flags)
>  {
>  	size_t bytes;
>  
> @@ -774,7 +774,7 @@ static inline __alloc_size(1, 2) void *kvcalloc(size_t n, size_t size, gfp_t fla
>  }
>  
>  extern void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags)
> -		      __alloc_size(3);
> +		      __realloc_size(3);
>  extern void kvfree(const void *addr);
>  extern void kvfree_sensitive(const void *addr, size_t len);
>  
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 17996649cfe3..457671ace7eb 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -1134,8 +1134,8 @@ module_init(slab_proc_init);
>  
>  #endif /* CONFIG_SLAB || CONFIG_SLUB_DEBUG */
>  
> -static __always_inline void *__do_krealloc(const void *p, size_t new_size,
> -					   gfp_t flags)
> +static __always_inline __realloc_size(2) void *
> +__do_krealloc(const void *p, size_t new_size, gfp_t flags)
>  {
>  	void *ret;
>  	size_t ks;
> -- 
> 2.34.1
> 

This is now squashed with later one. (so undefined __alloc_size__ issues are fixed)
for the latest version of this patch:

Looks good to me,
Acked-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
diff mbox series

Patch

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 4f2a819fd60a..f141a6f6b9f6 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -271,15 +271,12 @@  struct ftrace_likely_data {
 
 /*
  * Any place that could be marked with the "alloc_size" attribute is also
- * a place to be marked with the "malloc" attribute. Do this as part of the
- * __alloc_size macro to avoid redundant attributes and to avoid missing a
- * __malloc marking.
+ * a place to be marked with the "malloc" attribute, except those that may
+ * be performing a _reallocation_, as that may alias the existing pointer.
+ * For these, use __realloc_size().
  */
-#ifdef __alloc_size__
-# define __alloc_size(x, ...)	__alloc_size__(x, ## __VA_ARGS__) __malloc
-#else
-# define __alloc_size(x, ...)	__malloc
-#endif
+#define __alloc_size(x, ...)	__alloc_size__(x, ## __VA_ARGS__) __malloc
+#define __realloc_size(x, ...)	__alloc_size__(x, ## __VA_ARGS__)
 
 #ifndef asm_volatile_goto
 #define asm_volatile_goto(x...) asm goto(x)
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 0fefdf528e0d..41bd036e7551 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -184,7 +184,7 @@  int kmem_cache_shrink(struct kmem_cache *s);
 /*
  * Common kmalloc functions provided by all allocators
  */
-void * __must_check krealloc(const void *objp, size_t new_size, gfp_t flags) __alloc_size(2);
+void * __must_check krealloc(const void *objp, size_t new_size, gfp_t flags) __realloc_size(2);
 void kfree(const void *objp);
 void kfree_sensitive(const void *objp);
 size_t __ksize(const void *objp);
@@ -647,10 +647,10 @@  static inline __alloc_size(1, 2) void *kmalloc_array(size_t n, size_t size, gfp_
  * @new_size: new size of a single member of the array
  * @flags: the type of memory to allocate (see kmalloc)
  */
-static inline __alloc_size(2, 3) void * __must_check krealloc_array(void *p,
-								    size_t new_n,
-								    size_t new_size,
-								    gfp_t flags)
+static inline __realloc_size(2, 3) void * __must_check krealloc_array(void *p,
+								      size_t new_n,
+								      size_t new_size,
+								      gfp_t flags)
 {
 	size_t bytes;
 
@@ -774,7 +774,7 @@  static inline __alloc_size(1, 2) void *kvcalloc(size_t n, size_t size, gfp_t fla
 }
 
 extern void *kvrealloc(const void *p, size_t oldsize, size_t newsize, gfp_t flags)
-		      __alloc_size(3);
+		      __realloc_size(3);
 extern void kvfree(const void *addr);
 extern void kvfree_sensitive(const void *addr, size_t len);
 
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 17996649cfe3..457671ace7eb 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1134,8 +1134,8 @@  module_init(slab_proc_init);
 
 #endif /* CONFIG_SLAB || CONFIG_SLUB_DEBUG */
 
-static __always_inline void *__do_krealloc(const void *p, size_t new_size,
-					   gfp_t flags)
+static __always_inline __realloc_size(2) void *
+__do_krealloc(const void *p, size_t new_size, gfp_t flags)
 {
 	void *ret;
 	size_t ks;