Messages in this thread Patch in this message | | | Date | Thu, 26 Nov 2009 13:07:53 +0200 | From | Török Edwin <> | Subject | Memset of length zero bugs |
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On 2009-11-11 23:57, Dave Jones wrote: > Nearly every invocation of memset in drivers/staging/hv/StorVsc.c > has it's arguments the wrong way around. Hi,
I found 2 more bugs like this in v2.6.32-rc8-11-ga8a8a66 by letting gcc warn in such cases on an allyesconfig build. I used the attached patch (meant to be used only to find bugs, linking fails).
Here are the warnings: 1. Wrong parameter order In function ‘memset’, inlined from ‘ir_input_init’ at drivers/media/common/ir-functions.c:67: /home/edwin/builds/linux-2.6/arch/x86/include/asm/string_64.h:61: warning: call to ‘__warn_memset_zero_len’ declared with attribute warning: memset used with constant zero length parameter; this could be due to transposed parameters memset(ir->ir_codes, sizeof(ir->ir_codes), 0);
2. pgsize variable (and hence length argument) is always zero.
In function ‘memset’, inlined from ‘erasecrosstest’ at drivers/mtd/tests/mtd_pagetest.c:345: /home/edwin/builds/linux-2.6/arch/x86/include/asm/string_64.h:61: warning: call to ‘__warn_memset_zero_len’ declared with attribute warning: memset used with constant zero length parameter; this could be due to transposed parameters memset(readbuf, 0, pgsize); In function ‘memset’, inlined from ‘erasecrosstest’ at drivers/mtd/tests/mtd_pagetest.c:384: /home/edwin/builds/linux-2.6/arch/x86/include/asm/string_64.h:61: warning: call to ‘__warn_memset_zero_len’ declared with attribute warning: memset used with constant zero length parameter; this could be due to transposed parameters In function ‘memset’, inlined from ‘crosstest’ at drivers/mtd/tests/mtd_pagetest.c:219: /home/edwin/builds/linux-2.6/arch/x86/include/asm/string_64.h:61: warning: call to ‘__warn_memset_zero_len’ declared with attribute warning: memset used with constant zero length parameter; this could be due to transposed parameters
Now this one is interesting, the memsets are fine, however pgsize is always zero, it is declared as 'static int pgsize' and never assigned a value (hence it is always zero). I didn't look at what mtd_pagetest wants to test, but the name suggests that a pagesize of zero isn't a very useful test.
Best regards, --Edwin diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h index 19e2c46..cddefb7 100644 --- a/arch/x86/include/asm/string_64.h +++ b/arch/x86/include/asm/string_64.h @@ -52,7 +52,17 @@ extern void *__memcpy(void *to, const void *from, size_t len); #endif #define __HAVE_ARCH_MEMSET -void *memset(void *s, int c, size_t n); +extern void __warn_memset_zero_len (void) __attribute__((__warning__ ("memset used with constant zero length parameter; this could be due to transposed parameters"))); +extern __inline __attribute__ ((__always_inline__)) __attribute__ ((__artificial__)) void * +__attribute__ ((__nothrow__)) memset (void *__dest, int __ch, size_t __len) +{ + if (__builtin_constant_p (__len) && __len == 0) + { + __warn_memset_zero_len (); + return __dest; + } + return __builtin___memset_chk (__dest, __ch, __len, __builtin_object_size (__dest, 0)); +} #define __HAVE_ARCH_MEMMOVE void *memmove(void *dest, const void *src, size_t count); | |