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fortify: strlen: Avoid shadowing previous locals

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The __compiletime_strlen() macro expansion will shadow p_size and p_len
local variables. No callers currently use any of the shadowed names
for their "p" variable, so there are no code generation problems.

Add "__" prefixes to variable definitions __compiletime_strlen() to
avoid new W=2 warnings:

./include/linux/fortify-string.h: In function 'strnlen':
./include/linux/fortify-string.h:17:9: warning: declaration of 'p_size' shadows a previous local [-Wshadow]
   17 |  size_t p_size = __builtin_object_size(p, 1); \
      |         ^~~~~~
./include/linux/fortify-string.h:77:17: note: in expansion of macro '__compiletime_strlen'
   77 |  size_t p_len = __compiletime_strlen(p);
      |                 ^~~~~~~~~~~~~~~~~~~~
./include/linux/fortify-string.h:76:9: note: shadowed declaration is here
   76 |  size_t p_size = __builtin_object_size(p, 1);
      |         ^~~~~~

Signed-off-by: Qian Cai <quic_qiancai@quicinc.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20211025210528.261643-1-quic_qiancai@quicinc.com
This commit is contained in:
Qian Cai 2021-10-25 17:05:28 -04:00 committed by Kees Cook
parent 9a48e7564a
commit 95cadae320
1 changed files with 12 additions and 12 deletions
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24
include/linux/fortify-string.h
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@ -10,18 +10,18 @@ void __read_overflow(void) __compiletime_error("detected read beyond size of obj
void __read_overflow2(void) __compiletime_error("detected read beyond size of object (2nd parameter)");
void __write_overflow(void) __compiletime_error("detected write beyond size of object (1st parameter)");
#define __compiletime_strlen(p) \
({ \
unsigned char *__p = (unsigned char *)(p); \
size_t ret = (size_t)-1; \
size_t p_size = __builtin_object_size(p, 1); \
if (p_size != (size_t)-1) { \
size_t p_len = p_size - 1; \
if (__builtin_constant_p(__p[p_len]) && \
__p[p_len] == '\0') \
ret = __builtin_strlen(__p); \
} \
ret; \
#define __compiletime_strlen(p) \
({ \
unsigned char *__p = (unsigned char *)(p); \
size_t __ret = (size_t)-1; \
size_t __p_size = __builtin_object_size(p, 1); \
if (__p_size != (size_t)-1) { \
size_t __p_len = __p_size - 1; \
if (__builtin_constant_p(__p[__p_len]) && \
__p[__p_len] == '\0') \
__ret = __builtin_strlen(__p); \
} \
__ret; \
})
#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)