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Date: Tue, 18 Apr 2023 10:58:08 -0700
From: Nick Desaulniers <ndesaulniers@...gle.com>
To: Kees Cook <keescook@...omium.org>
Cc: linux-hardening@...r.kernel.org,
Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
Andy Shevchenko <andy@...nel.org>,
Cezary Rojewski <cezary.rojewski@...el.com>,
Puyou Lu <puyou.lu@...il.com>, Mark Brown <broonie@...nel.org>,
Josh Poimboeuf <jpoimboe@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Brendan Higgins <brendan.higgins@...ux.dev>,
David Gow <davidgow@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Nathan Chancellor <nathan@...nel.org>,
Alexander Potapenko <glider@...gle.com>,
Zhaoyang Huang <zhaoyang.huang@...soc.com>,
Randy Dunlap <rdunlap@...radead.org>,
Geert Uytterhoeven <geert+renesas@...der.be>,
Miguel Ojeda <ojeda@...nel.org>,
Alexander Lobakin <aleksander.lobakin@...el.com>,
Liam Howlett <liam.howlett@...cle.com>,
Vlastimil Babka <vbabka@...e.cz>,
Dan Williams <dan.j.williams@...el.com>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
Yury Norov <yury.norov@...il.com>,
"Jason A. Donenfeld" <Jason@...c4.com>,
Sander Vanheule <sander@...nheule.net>,
Eric Biggers <ebiggers@...gle.com>,
"Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
Andrey Konovalov <andreyknvl@...il.com>,
Linus Walleij <linus.walleij@...aro.org>,
Daniel Latypov <dlatypov@...gle.com>,
José Expósito <jose.exposito89@...il.com>,
linux-kernel@...r.kernel.org, kunit-dev@...glegroups.com
Subject: Re: [PATCH v2 04/10] fortify: Use const variables for __member_size tracking
On Fri, Apr 7, 2023 at 12:27 PM Kees Cook <keescook@...omium.org> wrote:
>
> The sizes reported by __member_size should never change in a given
> function. Mark them as such.
>
> Suggested-by: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
> ---
> include/linux/fortify-string.h | 42 +++++++++++++++++-----------------
> 1 file changed, 21 insertions(+), 21 deletions(-)
>
> diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
> index c9de1f59ee80..fae1bf4bd543 100644
> --- a/include/linux/fortify-string.h
> +++ b/include/linux/fortify-string.h
> @@ -20,7 +20,7 @@ void __write_overflow_field(size_t avail, size_t wanted) __compiletime_warning("
> ({ \
> char *__p = (char *)(p); \
> size_t __ret = SIZE_MAX; \
> - size_t __p_size = __member_size(p); \
> + const size_t __p_size = __member_size(p); \
> if (__p_size != SIZE_MAX && \
> __builtin_constant_p(*__p)) { \
> size_t __p_len = __p_size - 1; \
> @@ -142,7 +142,7 @@ extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size)
> __FORTIFY_INLINE __diagnose_as(__builtin_strncpy, 1, 2, 3)
> char *strncpy(char * const POS p, const char *q, __kernel_size_t size)
> {
> - size_t p_size = __member_size(p);
> + const size_t p_size = __member_size(p);
>
> if (__compiletime_lessthan(p_size, size))
> __write_overflow();
> @@ -169,7 +169,7 @@ char *strncpy(char * const POS p, const char *q, __kernel_size_t size)
> __FORTIFY_INLINE __diagnose_as(__builtin_strcat, 1, 2)
> char *strcat(char * const POS p, const char *q)
> {
> - size_t p_size = __member_size(p);
> + const size_t p_size = __member_size(p);
>
> if (p_size == SIZE_MAX)
> return __underlying_strcat(p, q);
> @@ -191,8 +191,8 @@ extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(st
> */
> __FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size_t maxlen)
> {
> - size_t p_size = __member_size(p);
> - size_t p_len = __compiletime_strlen(p);
> + const size_t p_size = __member_size(p);
> + const size_t p_len = __compiletime_strlen(p);
> size_t ret;
>
> /* We can take compile-time actions when maxlen is const. */
> @@ -233,8 +233,8 @@ __FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size
> __FORTIFY_INLINE __diagnose_as(__builtin_strlen, 1)
> __kernel_size_t __fortify_strlen(const char * const POS p)
> {
> + const size_t p_size = __member_size(p);
> __kernel_size_t ret;
> - size_t p_size = __member_size(p);
>
> /* Give up if we don't know how large p is. */
> if (p_size == SIZE_MAX)
> @@ -267,8 +267,8 @@ extern size_t __real_strlcpy(char *, const char *, size_t) __RENAME(strlcpy);
> */
> __FORTIFY_INLINE size_t strlcpy(char * const POS p, const char * const POS q, size_t size)
> {
> - size_t p_size = __member_size(p);
> - size_t q_size = __member_size(q);
> + const size_t p_size = __member_size(p);
> + const size_t q_size = __member_size(q);
> size_t q_len; /* Full count of source string length. */
> size_t len; /* Count of characters going into destination. */
>
> @@ -318,10 +318,10 @@ extern ssize_t __real_strscpy(char *, const char *, size_t) __RENAME(strscpy);
> */
> __FORTIFY_INLINE ssize_t strscpy(char * const POS p, const char * const POS q, size_t size)
> {
> - size_t len;
> /* Use string size rather than possible enclosing struct size. */
> - size_t p_size = __member_size(p);
> - size_t q_size = __member_size(q);
> + const size_t p_size = __member_size(p);
> + const size_t q_size = __member_size(q);
> + size_t len;
>
> /* If we cannot get size of p and q default to call strscpy. */
> if (p_size == SIZE_MAX && q_size == SIZE_MAX)
> @@ -394,9 +394,9 @@ __FORTIFY_INLINE ssize_t strscpy(char * const POS p, const char * const POS q, s
> __FORTIFY_INLINE __diagnose_as(__builtin_strncat, 1, 2, 3)
> char *strncat(char * const POS p, const char * const POS q, __kernel_size_t count)
> {
> + const size_t p_size = __member_size(p);
> + const size_t q_size = __member_size(q);
> size_t p_len, copy_len;
> - size_t p_size = __member_size(p);
> - size_t q_size = __member_size(q);
>
> if (p_size == SIZE_MAX && q_size == SIZE_MAX)
> return __underlying_strncat(p, q, count);
> @@ -639,7 +639,7 @@ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size,
> extern void *__real_memscan(void *, int, __kernel_size_t) __RENAME(memscan);
> __FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size)
> {
> - size_t p_size = __struct_size(p);
> + const size_t p_size = __struct_size(p);
>
> if (__compiletime_lessthan(p_size, size))
> __read_overflow();
> @@ -651,8 +651,8 @@ __FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size)
> __FORTIFY_INLINE __diagnose_as(__builtin_memcmp, 1, 2, 3)
> int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t size)
> {
> - size_t p_size = __struct_size(p);
> - size_t q_size = __struct_size(q);
> + const size_t p_size = __struct_size(p);
> + const size_t q_size = __struct_size(q);
>
> if (__builtin_constant_p(size)) {
> if (__compiletime_lessthan(p_size, size))
> @@ -668,7 +668,7 @@ int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t
> __FORTIFY_INLINE __diagnose_as(__builtin_memchr, 1, 2, 3)
> void *memchr(const void * const POS0 p, int c, __kernel_size_t size)
> {
> - size_t p_size = __struct_size(p);
> + const size_t p_size = __struct_size(p);
>
> if (__compiletime_lessthan(p_size, size))
> __read_overflow();
> @@ -680,7 +680,7 @@ void *memchr(const void * const POS0 p, int c, __kernel_size_t size)
> void *__real_memchr_inv(const void *s, int c, size_t n) __RENAME(memchr_inv);
> __FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size)
> {
> - size_t p_size = __struct_size(p);
> + const size_t p_size = __struct_size(p);
>
> if (__compiletime_lessthan(p_size, size))
> __read_overflow();
> @@ -693,7 +693,7 @@ extern void *__real_kmemdup(const void *src, size_t len, gfp_t gfp) __RENAME(kme
> __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);
> + const size_t p_size = __struct_size(p);
>
> if (__compiletime_lessthan(p_size, size))
> __read_overflow();
> @@ -720,8 +720,8 @@ __FORTIFY_INLINE void *kmemdup(const void * const POS0 p, size_t size, gfp_t gfp
> __FORTIFY_INLINE __diagnose_as(__builtin_strcpy, 1, 2)
> char *strcpy(char * const POS p, const char * const POS q)
> {
> - size_t p_size = __member_size(p);
> - size_t q_size = __member_size(q);
> + const size_t p_size = __member_size(p);
> + const size_t q_size = __member_size(q);
> size_t size;
>
> /* If neither buffer size is known, immediately give up. */
> --
> 2.34.1
>
--
Thanks,
~Nick Desaulniers
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