Messages in this thread Patch in this message | | | Subject | Re: Re: [PATCH v2] arm64: kasan: add interceptors for strcmp/strncmp functions | From | Kyeongdon Kim <> | Date | Tue, 4 Sep 2018 15:59:17 +0900 |
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Hello Andrey,
Thanks for your review.
On 2018-09-03 오후 6:40, Andrey Ryabinin wrote: > > > On 08/23/2018 11:56 AM, Kyeongdon Kim wrote: > > > diff --git a/mm/kasan/kasan.c b/mm/kasan/kasan.c > > index c3bd520..61ad7f1 100644 > > --- a/mm/kasan/kasan.c > > +++ b/mm/kasan/kasan.c > > @@ -304,6 +304,29 @@ void *memcpy(void *dest, const void *src, > size_t len) > > > > return __memcpy(dest, src, len); > > } > > +#ifdef CONFIG_ARM64 > > +/* > > + * Arch arm64 use assembly variant for strcmp/strncmp, > > + * xtensa use inline asm operations and x86_64 use c one, > > + * so now this interceptors only for arm64 kasan. > > + */ > > +#undef strcmp > > +int strcmp(const char *cs, const char *ct) > > +{ > > + check_memory_region((unsigned long)cs, 1, false, _RET_IP_); > > + check_memory_region((unsigned long)ct, 1, false, _RET_IP_); > > + > > Well this is definitely wrong. strcmp() often accesses far more than > one byte. > > > + return __strcmp(cs, ct); > > +} > > +#undef strncmp > > +int strncmp(const char *cs, const char *ct, size_t len) > > +{ > > + check_memory_region((unsigned long)cs, len, false, _RET_IP_); > > + check_memory_region((unsigned long)ct, len, false, _RET_IP_); > > This will cause false positives. Both 'cs', and 'ct' could be less > than len bytes. > > There is no need in these interceptors, just use the C implementations > from lib/string.c > like you did in your first patch. > The only thing that was wrong in the first patch is that assembly > implementations > were compiled out instead of being declared week. > Well, at first I thought so.. I would remove diff code in /mm/kasan/kasan.c then use C implementations in lib/string.c w/ assem implementations as weak :
diff --git a/lib/string.c b/lib/string.c index 2c0900a..a18b18f 100644 --- a/lib/string.c +++ b/lib/string.c @@ -312,7 +312,7 @@ size_t strlcat(char *dest, const char *src, size_t count) EXPORT_SYMBOL(strlcat); #endif
-#ifndef __HAVE_ARCH_STRCMP +#if (defined(CONFIG_ARM64) && defined(CONFIG_KASAN)) || !defined(__HAVE_ARCH_STRCMP) /** * strcmp - Compare two strings * @cs: One string @@ -336,7 +336,7 @@ int strcmp(const char *cs, const char *ct) EXPORT_SYMBOL(strcmp); #endif
-#ifndef __HAVE_ARCH_STRNCMP +#if (defined(CONFIG_ARM64) && defined(CONFIG_KASAN)) || !defined(__HAVE_ARCH_STRNCMP) /** * strncmp - Compare two length-limited strings
Can I get your opinion wrt this ? Thanks,
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