diff mbox series

[4/6] string: Add __realloc_size hint to kmemdup()

Message ID 20221101223321.1326815-4-keescook@chromium.org
State New
Headers
Series slab: Provide full coverage for __alloc_size attribute |

Commit Message

Kees Cook Nov. 1, 2022, 10:33 p.m. UTC 
  Add __realloc_size() hint to kmemdup() so the compiler can reason about
the length of the returned buffer. (These must not use __alloc_size,
since those include __malloc which says the contents aren't defined[1]).

[1] https://lore.kernel.org/linux-hardening/d199c2af-06af-8a50-a6a1-00eefa0b67b4@prevas.dk/

Cc: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Andy Shevchenko <andriy.shevchenko@intel.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/fortify-string.h | 2 +-
 include/linux/string.h         | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

Comments

Rasmus Villemoes Nov. 2, 2022, 9:26 a.m. UTC | #1 
On 01/11/2022 23.33, Kees Cook wrote:
> Add __realloc_size() hint to kmemdup() so the compiler can reason about
> the length of the returned buffer. (These must not use __alloc_size,
> since those include __malloc which says the contents aren't defined[1]).
> 
> [1] https://lore.kernel.org/linux-hardening/d199c2af-06af-8a50-a6a1-00eefa0b67b4@prevas.dk/
> 

>  extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
> -extern void *kmemdup(const void *src, size_t len, gfp_t gfp) __alloc_size(2);
> +extern void *kmemdup(const void *src, size_t len, gfp_t gfp) __realloc_size(2);

What tree is this based on? I see that kmemdup() has grown that bogus
__alloc_size in next-20221101, but in next-20221102 this commit seems to
DTRT, namely

-extern void *kmemdup(const void *src, size_t len, gfp_t gfp);
+extern void *kmemdup(const void *src, size_t len, gfp_t gfp)
__realloc_size(2);

(i.e. there should never be an intermediate commit where kmemdup has
__alloc_size()).

Rasmus
Kees Cook Nov. 2, 2022, 7:40 p.m. UTC | #2 
On Wed, Nov 02, 2022 at 10:26:40AM +0100, Rasmus Villemoes wrote:
> On 01/11/2022 23.33, Kees Cook wrote:
> > Add __realloc_size() hint to kmemdup() so the compiler can reason about
> > the length of the returned buffer. (These must not use __alloc_size,
> > since those include __malloc which says the contents aren't defined[1]).
> > 
> > [1] https://lore.kernel.org/linux-hardening/d199c2af-06af-8a50-a6a1-00eefa0b67b4@prevas.dk/
> > 
> 
> >  extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
> > -extern void *kmemdup(const void *src, size_t len, gfp_t gfp) __alloc_size(2);
> > +extern void *kmemdup(const void *src, size_t len, gfp_t gfp) __realloc_size(2);
> 
> What tree is this based on? I see that kmemdup() has grown that bogus
> __alloc_size in next-20221101, but in next-20221102 this commit seems to
> DTRT, namely
> 
> -extern void *kmemdup(const void *src, size_t len, gfp_t gfp);
> +extern void *kmemdup(const void *src, size_t len, gfp_t gfp)
> __realloc_size(2);
> 
> (i.e. there should never be an intermediate commit where kmemdup has
> __alloc_size()).

Right -- I fixed in in my -next tree to not use __alloc_size.
diff mbox series

Patch

diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
index 9e2d96993c30..aa31f54f8b57 100644
--- a/include/linux/fortify-string.h
+++ b/include/linux/fortify-string.h
@@ -670,7 +670,7 @@  __FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size)
 }
 
 extern void *__real_kmemdup(const void *src, size_t len, gfp_t gfp) __RENAME(kmemdup)
-								    __alloc_size(2);
+								    __realloc_size(2);
 __FORTIFY_INLINE void *kmemdup(const void * const POS0 p, size_t size, gfp_t gfp)
 {
 	size_t p_size = __struct_size(p);
diff --git a/include/linux/string.h b/include/linux/string.h
index af1d69e5610e..db28802ab0a6 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -176,7 +176,7 @@  extern void kfree_const(const void *x);
 extern char *kstrdup(const char *s, gfp_t gfp) __malloc;
 extern const char *kstrdup_const(const char *s, gfp_t gfp);
 extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
-extern void *kmemdup(const void *src, size_t len, gfp_t gfp) __alloc_size(2);
+extern void *kmemdup(const void *src, size_t len, gfp_t gfp) __realloc_size(2);
 extern char *kmemdup_nul(const char *s, size_t len, gfp_t gfp);
 
 extern char **argv_split(gfp_t gfp, const char *str, int *argcp);