linux_dsm_epyc7002/arch/x86/include/asm/string_32.h
Daniel Micay 6974f0c455 include/linux/string.h: add the option of fortified string.h functions
This adds support for compiling with a rough equivalent to the glibc
_FORTIFY_SOURCE=1 feature, providing compile-time and runtime buffer
overflow checks for string.h functions when the compiler determines the
size of the source or destination buffer at compile-time.  Unlike glibc,
it covers buffer reads in addition to writes.

GNU C __builtin_*_chk intrinsics are avoided because they would force a
much more complex implementation.  They aren't designed to detect read
overflows and offer no real benefit when using an implementation based
on inline checks.  Inline checks don't add up to much code size and
allow full use of the regular string intrinsics while avoiding the need
for a bunch of _chk functions and per-arch assembly to avoid wrapper
overhead.

This detects various overflows at compile-time in various drivers and
some non-x86 core kernel code.  There will likely be issues caught in
regular use at runtime too.

Future improvements left out of initial implementation for simplicity,
as it's all quite optional and can be done incrementally:

* Some of the fortified string functions (strncpy, strcat), don't yet
  place a limit on reads from the source based on __builtin_object_size of
  the source buffer.

* Extending coverage to more string functions like strlcat.

* It should be possible to optionally use __builtin_object_size(x, 1) for
  some functions (C strings) to detect intra-object overflows (like
  glibc's _FORTIFY_SOURCE=2), but for now this takes the conservative
  approach to avoid likely compatibility issues.

* The compile-time checks should be made available via a separate config
  option which can be enabled by default (or always enabled) once enough
  time has passed to get the issues it catches fixed.

Kees said:
 "This is great to have. While it was out-of-tree code, it would have
  blocked at least CVE-2016-3858 from being exploitable (improper size
  argument to strlcpy()). I've sent a number of fixes for
  out-of-bounds-reads that this detected upstream already"

[arnd@arndb.de: x86: fix fortified memcpy]
  Link: http://lkml.kernel.org/r/20170627150047.660360-1-arnd@arndb.de
[keescook@chromium.org: avoid panic() in favor of BUG()]
  Link: http://lkml.kernel.org/r/20170626235122.GA25261@beast
[keescook@chromium.org: move from -mm, add ARCH_HAS_FORTIFY_SOURCE, tweak Kconfig help]
Link: http://lkml.kernel.org/r/20170526095404.20439-1-danielmicay@gmail.com
Link: http://lkml.kernel.org/r/1497903987-21002-8-git-send-email-keescook@chromium.org
Signed-off-by: Daniel Micay <danielmicay@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Daniel Axtens <dja@axtens.net>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-07-12 16:26:03 -07:00

352 lines
8.0 KiB
C

#ifndef _ASM_X86_STRING_32_H
#define _ASM_X86_STRING_32_H
#ifdef __KERNEL__
/* Let gcc decide whether to inline or use the out of line functions */
#define __HAVE_ARCH_STRCPY
extern char *strcpy(char *dest, const char *src);
#define __HAVE_ARCH_STRNCPY
extern char *strncpy(char *dest, const char *src, size_t count);
#define __HAVE_ARCH_STRCAT
extern char *strcat(char *dest, const char *src);
#define __HAVE_ARCH_STRNCAT
extern char *strncat(char *dest, const char *src, size_t count);
#define __HAVE_ARCH_STRCMP
extern int strcmp(const char *cs, const char *ct);
#define __HAVE_ARCH_STRNCMP
extern int strncmp(const char *cs, const char *ct, size_t count);
#define __HAVE_ARCH_STRCHR
extern char *strchr(const char *s, int c);
#define __HAVE_ARCH_STRLEN
extern size_t strlen(const char *s);
static __always_inline void *__memcpy(void *to, const void *from, size_t n)
{
int d0, d1, d2;
asm volatile("rep ; movsl\n\t"
"movl %4,%%ecx\n\t"
"andl $3,%%ecx\n\t"
"jz 1f\n\t"
"rep ; movsb\n\t"
"1:"
: "=&c" (d0), "=&D" (d1), "=&S" (d2)
: "0" (n / 4), "g" (n), "1" ((long)to), "2" ((long)from)
: "memory");
return to;
}
/*
* This looks ugly, but the compiler can optimize it totally,
* as the count is constant.
*/
static __always_inline void *__constant_memcpy(void *to, const void *from,
size_t n)
{
long esi, edi;
if (!n)
return to;
switch (n) {
case 1:
*(char *)to = *(char *)from;
return to;
case 2:
*(short *)to = *(short *)from;
return to;
case 4:
*(int *)to = *(int *)from;
return to;
case 3:
*(short *)to = *(short *)from;
*((char *)to + 2) = *((char *)from + 2);
return to;
case 5:
*(int *)to = *(int *)from;
*((char *)to + 4) = *((char *)from + 4);
return to;
case 6:
*(int *)to = *(int *)from;
*((short *)to + 2) = *((short *)from + 2);
return to;
case 8:
*(int *)to = *(int *)from;
*((int *)to + 1) = *((int *)from + 1);
return to;
}
esi = (long)from;
edi = (long)to;
if (n >= 5 * 4) {
/* large block: use rep prefix */
int ecx;
asm volatile("rep ; movsl"
: "=&c" (ecx), "=&D" (edi), "=&S" (esi)
: "0" (n / 4), "1" (edi), "2" (esi)
: "memory"
);
} else {
/* small block: don't clobber ecx + smaller code */
if (n >= 4 * 4)
asm volatile("movsl"
: "=&D"(edi), "=&S"(esi)
: "0"(edi), "1"(esi)
: "memory");
if (n >= 3 * 4)
asm volatile("movsl"
: "=&D"(edi), "=&S"(esi)
: "0"(edi), "1"(esi)
: "memory");
if (n >= 2 * 4)
asm volatile("movsl"
: "=&D"(edi), "=&S"(esi)
: "0"(edi), "1"(esi)
: "memory");
if (n >= 1 * 4)
asm volatile("movsl"
: "=&D"(edi), "=&S"(esi)
: "0"(edi), "1"(esi)
: "memory");
}
switch (n % 4) {
/* tail */
case 0:
return to;
case 1:
asm volatile("movsb"
: "=&D"(edi), "=&S"(esi)
: "0"(edi), "1"(esi)
: "memory");
return to;
case 2:
asm volatile("movsw"
: "=&D"(edi), "=&S"(esi)
: "0"(edi), "1"(esi)
: "memory");
return to;
default:
asm volatile("movsw\n\tmovsb"
: "=&D"(edi), "=&S"(esi)
: "0"(edi), "1"(esi)
: "memory");
return to;
}
}
#define __HAVE_ARCH_MEMCPY
extern void *memcpy(void *, const void *, size_t);
#ifndef CONFIG_FORTIFY_SOURCE
#ifdef CONFIG_X86_USE_3DNOW
#include <asm/mmx.h>
/*
* This CPU favours 3DNow strongly (eg AMD Athlon)
*/
static inline void *__constant_memcpy3d(void *to, const void *from, size_t len)
{
if (len < 512)
return __constant_memcpy(to, from, len);
return _mmx_memcpy(to, from, len);
}
static inline void *__memcpy3d(void *to, const void *from, size_t len)
{
if (len < 512)
return __memcpy(to, from, len);
return _mmx_memcpy(to, from, len);
}
#define memcpy(t, f, n) \
(__builtin_constant_p((n)) \
? __constant_memcpy3d((t), (f), (n)) \
: __memcpy3d((t), (f), (n)))
#else
/*
* No 3D Now!
*/
#ifndef CONFIG_KMEMCHECK
#if (__GNUC__ >= 4)
#define memcpy(t, f, n) __builtin_memcpy(t, f, n)
#else
#define memcpy(t, f, n) \
(__builtin_constant_p((n)) \
? __constant_memcpy((t), (f), (n)) \
: __memcpy((t), (f), (n)))
#endif
#else
/*
* kmemcheck becomes very happy if we use the REP instructions unconditionally,
* because it means that we know both memory operands in advance.
*/
#define memcpy(t, f, n) __memcpy((t), (f), (n))
#endif
#endif
#endif /* !CONFIG_FORTIFY_SOURCE */
#define __HAVE_ARCH_MEMMOVE
void *memmove(void *dest, const void *src, size_t n);
extern int memcmp(const void *, const void *, size_t);
#ifndef CONFIG_FORTIFY_SOURCE
#define memcmp __builtin_memcmp
#endif
#define __HAVE_ARCH_MEMCHR
extern void *memchr(const void *cs, int c, size_t count);
static inline void *__memset_generic(void *s, char c, size_t count)
{
int d0, d1;
asm volatile("rep\n\t"
"stosb"
: "=&c" (d0), "=&D" (d1)
: "a" (c), "1" (s), "0" (count)
: "memory");
return s;
}
/* we might want to write optimized versions of these later */
#define __constant_count_memset(s, c, count) __memset_generic((s), (c), (count))
/*
* memset(x, 0, y) is a reasonably common thing to do, so we want to fill
* things 32 bits at a time even when we don't know the size of the
* area at compile-time..
*/
static __always_inline
void *__constant_c_memset(void *s, unsigned long c, size_t count)
{
int d0, d1;
asm volatile("rep ; stosl\n\t"
"testb $2,%b3\n\t"
"je 1f\n\t"
"stosw\n"
"1:\ttestb $1,%b3\n\t"
"je 2f\n\t"
"stosb\n"
"2:"
: "=&c" (d0), "=&D" (d1)
: "a" (c), "q" (count), "0" (count/4), "1" ((long)s)
: "memory");
return s;
}
/* Added by Gertjan van Wingerde to make minix and sysv module work */
#define __HAVE_ARCH_STRNLEN
extern size_t strnlen(const char *s, size_t count);
/* end of additional stuff */
#define __HAVE_ARCH_STRSTR
extern char *strstr(const char *cs, const char *ct);
/*
* This looks horribly ugly, but the compiler can optimize it totally,
* as we by now know that both pattern and count is constant..
*/
static __always_inline
void *__constant_c_and_count_memset(void *s, unsigned long pattern,
size_t count)
{
switch (count) {
case 0:
return s;
case 1:
*(unsigned char *)s = pattern & 0xff;
return s;
case 2:
*(unsigned short *)s = pattern & 0xffff;
return s;
case 3:
*(unsigned short *)s = pattern & 0xffff;
*((unsigned char *)s + 2) = pattern & 0xff;
return s;
case 4:
*(unsigned long *)s = pattern;
return s;
}
#define COMMON(x) \
asm volatile("rep ; stosl" \
x \
: "=&c" (d0), "=&D" (d1) \
: "a" (eax), "0" (count/4), "1" ((long)s) \
: "memory")
{
int d0, d1;
#if __GNUC__ == 4 && __GNUC_MINOR__ == 0
/* Workaround for broken gcc 4.0 */
register unsigned long eax asm("%eax") = pattern;
#else
unsigned long eax = pattern;
#endif
switch (count % 4) {
case 0:
COMMON("");
return s;
case 1:
COMMON("\n\tstosb");
return s;
case 2:
COMMON("\n\tstosw");
return s;
default:
COMMON("\n\tstosw\n\tstosb");
return s;
}
}
#undef COMMON
}
#define __constant_c_x_memset(s, c, count) \
(__builtin_constant_p(count) \
? __constant_c_and_count_memset((s), (c), (count)) \
: __constant_c_memset((s), (c), (count)))
#define __memset(s, c, count) \
(__builtin_constant_p(count) \
? __constant_count_memset((s), (c), (count)) \
: __memset_generic((s), (c), (count)))
#define __HAVE_ARCH_MEMSET
extern void *memset(void *, int, size_t);
#ifndef CONFIG_FORTIFY_SOURCE
#if (__GNUC__ >= 4)
#define memset(s, c, count) __builtin_memset(s, c, count)
#else
#define memset(s, c, count) \
(__builtin_constant_p(c) \
? __constant_c_x_memset((s), (0x01010101UL * (unsigned char)(c)), \
(count)) \
: __memset((s), (c), (count)))
#endif
#endif /* !CONFIG_FORTIFY_SOURCE */
/*
* find the first occurrence of byte 'c', or 1 past the area if none
*/
#define __HAVE_ARCH_MEMSCAN
extern void *memscan(void *addr, int c, size_t size);
#endif /* __KERNEL__ */
#endif /* _ASM_X86_STRING_32_H */