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    Subject[PATCH AUTOSEL 5.3 106/203] s390/kasan: provide uninstrumented __strlen
    Date
    From: Vasily Gorbik <gor@linux.ibm.com>

    [ Upstream commit f45f7b5bdaa4828ce871cf03f7c01599a0de57a5 ]

    s390 kasan code uses sclp_early_printk to report initialization
    failures. The code doing that should not be instrumented, because kasan
    shadow memory has not been set up yet. Even though sclp_early_core.c is
    compiled with instrumentation disabled it uses strlen function, which
    is instrumented and would produce shadow memory access if used. To
    avoid that, introduce uninstrumented __strlen function to be used
    instead.

    Before commit 7e0d92f00246 ("s390/kasan: improve string/memory functions
    checks") few string functions (including strlen) were escaping kasan
    instrumentation due to usage of platform specific versions which are
    implemented in inline assembly.

    Fixes: 7e0d92f00246 ("s390/kasan: improve string/memory functions checks")
    Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
    Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/s390/include/asm/string.h | 9 +++++++--
    1 file changed, 7 insertions(+), 2 deletions(-)

    diff --git a/arch/s390/include/asm/string.h b/arch/s390/include/asm/string.h
    index 70d87db54e627..4c0690fc5167e 100644
    --- a/arch/s390/include/asm/string.h
    +++ b/arch/s390/include/asm/string.h
    @@ -71,11 +71,16 @@ extern void *__memmove(void *dest, const void *src, size_t n);
    #define memcpy(dst, src, len) __memcpy(dst, src, len)
    #define memmove(dst, src, len) __memmove(dst, src, len)
    #define memset(s, c, n) __memset(s, c, n)
    +#define strlen(s) __strlen(s)
    +
    +#define __no_sanitize_prefix_strfunc(x) __##x

    #ifndef __NO_FORTIFY
    #define __NO_FORTIFY /* FORTIFY_SOURCE uses __builtin_memcpy, etc. */
    #endif

    +#else
    +#define __no_sanitize_prefix_strfunc(x) x
    #endif /* defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__) */

    void *__memset16(uint16_t *s, uint16_t v, size_t count);
    @@ -163,8 +168,8 @@ static inline char *strcpy(char *dst, const char *src)
    }
    #endif

    -#ifdef __HAVE_ARCH_STRLEN
    -static inline size_t strlen(const char *s)
    +#if defined(__HAVE_ARCH_STRLEN) || (defined(CONFIG_KASAN) && !defined(__SANITIZE_ADDRESS__))
    +static inline size_t __no_sanitize_prefix_strfunc(strlen)(const char *s)
    {
    register unsigned long r0 asm("0") = 0;
    const char *tmp = s;
    --
    2.20.1
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