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Message-Id: <20230406000212.3442647-6-keescook@chromium.org>
Date: Wed, 5 Apr 2023 17:02:05 -0700
From: Kees Cook <keescook@...omium.org>
To: linux-hardening@...r.kernel.org
Cc: Kees Cook <keescook@...omium.org>,
Andy Shevchenko <andy@...nel.org>,
Cezary Rojewski <cezary.rojewski@...el.com>,
Puyou Lu <puyou.lu@...il.com>, Mark Brown <broonie@...nel.org>,
Josh Poimboeuf <jpoimboe@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Brendan Higgins <brendan.higgins@...ux.dev>,
David Gow <davidgow@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Nathan Chancellor <nathan@...nel.org>,
Alexander Potapenko <glider@...gle.com>,
Zhaoyang Huang <zhaoyang.huang@...soc.com>,
Randy Dunlap <rdunlap@...radead.org>,
Geert Uytterhoeven <geert+renesas@...der.be>,
Miguel Ojeda <ojeda@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Liam Howlett <liam.howlett@...cle.com>,
Vlastimil Babka <vbabka@...e.cz>,
Dan Williams <dan.j.williams@...el.com>,
Rasmus Villemoes <linux@...musvillemoes.dk>,
Yury Norov <yury.norov@...il.com>,
"Jason A. Donenfeld" <Jason@...c4.com>,
Sander Vanheule <sander@...nheule.net>,
Eric Biggers <ebiggers@...gle.com>,
"Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
Andrey Konovalov <andreyknvl@...il.com>,
Linus Walleij <linus.walleij@...aro.org>,
Daniel Latypov <dlatypov@...gle.com>,
José Expósito <jose.exposito89@...il.com>,
linux-kernel@...r.kernel.org, kunit-dev@...glegroups.com
Subject: [PATCH 6/9] fortify: Split reporting and avoid passing string pointer
In preparation for KUnit testing and further improvements in fortify
failure reporting, split out the report and encode the function and
access failure (read or write overflow) into a single int argument. This
mainly ends up saving some space in the data segment. For a defconfig
with FORTIFY_SOURCE enabled:
$ size gcc/vmlinux.before gcc/vmlinux.after
text data bss dec hex filename
26132309 9760658 2195460 38088427 2452eeb gcc/vmlinux.before
26132386 9748382 2195460 38076228 244ff44 gcc/vmlinux.after
Cc: Andy Shevchenko <andy@...nel.org>
Cc: Cezary Rojewski <cezary.rojewski@...el.com>
Cc: Puyou Lu <puyou.lu@...il.com>
Cc: Mark Brown <broonie@...nel.org>
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
include/linux/fortify-string.h | 72 +++++++++++++++++++++++-----------
lib/string_helpers.c | 70 +++++++++++++++++++++++++++++++--
tools/objtool/check.c | 2 +-
3 files changed, 118 insertions(+), 26 deletions(-)
diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
index 41dbd641f55c..6db4052db459 100644
--- a/include/linux/fortify-string.h
+++ b/include/linux/fortify-string.h
@@ -9,7 +9,34 @@
#define __FORTIFY_INLINE extern __always_inline __gnu_inline __overloadable
#define __RENAME(x) __asm__(#x)
-void fortify_panic(const char *name) __noreturn __cold;
+#define fortify_reason(func, write) (((func) << 1) | !!(write))
+
+#define fortify_panic(func, write) \
+ __fortify_panic(fortify_reason(func, write))
+
+#define FORTIFY_READ 0
+#define FORTIFY_WRITE 1
+
+#define FORTIFY_FUNC_strncpy 0
+#define FORTIFY_FUNC_strnlen 1
+#define FORTIFY_FUNC_strlen 2
+#define FORTIFY_FUNC_strlcpy 3
+#define FORTIFY_FUNC_strscpy 4
+#define FORTIFY_FUNC_strlcat 5
+#define FORTIFY_FUNC_strcat 6
+#define FORTIFY_FUNC_strncat 7
+#define FORTIFY_FUNC_memset 8
+#define FORTIFY_FUNC_memcpy 9
+#define FORTIFY_FUNC_memmove 10
+#define FORTIFY_FUNC_memscan 11
+#define FORTIFY_FUNC_memcmp 12
+#define FORTIFY_FUNC_memchr 13
+#define FORTIFY_FUNC_memchr_inv 14
+#define FORTIFY_FUNC_kmemdup 15
+#define FORTIFY_FUNC_strcpy 16
+
+void __fortify_report(u8 reason);
+void __fortify_panic(u8 reason) __cold __noreturn;
void __read_overflow(void) __compiletime_error("detected read beyond size of object (1st parameter)");
void __read_overflow2(void) __compiletime_error("detected read beyond size of object (2nd parameter)");
void __read_overflow2_field(size_t avail, size_t wanted) __compiletime_warning("detected read beyond size of field (2nd parameter); maybe use struct_group()?");
@@ -147,7 +174,7 @@ char *strncpy(char * const POS p, const char *q, __kernel_size_t size)
if (__compiletime_lessthan(p_size, size))
__write_overflow();
if (p_size < size)
- fortify_panic(__func__);
+ fortify_panic(FORTIFY_FUNC_strncpy, FORTIFY_WRITE);
return __underlying_strncpy(p, q, size);
}
@@ -178,7 +205,7 @@ __FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size
/* Do not check characters beyond the end of p. */
ret = __real_strnlen(p, maxlen < p_size ? maxlen : p_size);
if (p_size <= ret && maxlen != ret)
- fortify_panic(__func__);
+ fortify_panic(FORTIFY_FUNC_strnlen, FORTIFY_READ);
return ret;
}
@@ -214,7 +241,7 @@ __kernel_size_t __fortify_strlen(const char * const POS p)
return __underlying_strlen(p);
ret = strnlen(p, p_size);
if (p_size <= ret)
- fortify_panic(__func__);
+ fortify_panic(FORTIFY_FUNC_strlen, FORTIFY_READ);
return ret;
}
@@ -256,7 +283,7 @@ __FORTIFY_INLINE size_t strlcpy(char * const POS p, const char * const POS q, si
}
if (size) {
if (len >= p_size)
- fortify_panic(__func__);
+ fortify_panic(FORTIFY_FUNC_strlcpy, FORTIFY_WRITE);
__underlying_memcpy(p, q, len);
p[len] = '\0';
}
@@ -334,7 +361,7 @@ __FORTIFY_INLINE ssize_t strscpy(char * const POS p, const char * const POS q, s
* p_size.
*/
if (len > p_size)
- fortify_panic(__func__);
+ fortify_panic(FORTIFY_FUNC_strscpy, FORTIFY_WRITE);
/*
* We can now safely call vanilla strscpy because we are protected from:
@@ -392,7 +419,7 @@ size_t strlcat(char * const POS p, const char * const POS q, size_t avail)
/* Give up if string is already overflowed. */
if (p_size <= p_len)
- fortify_panic(__func__);
+ fortify_panic(FORTIFY_FUNC_strlcat, FORTIFY_READ);
if (actual >= avail) {
copy_len = avail - p_len - 1;
@@ -401,7 +428,7 @@ size_t strlcat(char * const POS p, const char * const POS q, size_t avail)
/* Give up if copy will overflow. */
if (p_size <= actual)
- fortify_panic(__func__);
+ fortify_panic(FORTIFY_FUNC_strlcat, FORTIFY_WRITE);
__underlying_memcpy(p + p_len, q, copy_len);
p[actual] = '\0';
@@ -430,7 +457,7 @@ char *strcat(char * const POS p, const char *q)
size_t p_size = __member_size(p);
if (strlcat(p, q, p_size) >= p_size)
- fortify_panic(__func__);
+ fortify_panic(FORTIFY_FUNC_strcat, FORTIFY_WRITE);
return p;
}
@@ -466,7 +493,7 @@ char *strncat(char * const POS p, const char * const POS q, __kernel_size_t coun
p_len = strlen(p);
copy_len = strnlen(q, count);
if (p_size < p_len + copy_len + 1)
- fortify_panic(__func__);
+ fortify_panic(FORTIFY_FUNC_strncat, FORTIFY_WRITE);
__underlying_memcpy(p + p_len, q, copy_len);
p[p_len + copy_len] = '\0';
return p;
@@ -507,7 +534,7 @@ __FORTIFY_INLINE void fortify_memset_chk(__kernel_size_t size,
* lengths are unknown.)
*/
if (p_size != SIZE_MAX && p_size < size)
- fortify_panic("memset");
+ fortify_panic(FORTIFY_FUNC_memset, FORTIFY_WRITE);
}
#define __fortify_memset_chk(p, c, size, p_size, p_size_field) ({ \
@@ -561,7 +588,7 @@ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size,
const size_t q_size,
const size_t p_size_field,
const size_t q_size_field,
- const char *func)
+ const u8 func)
{
if (__builtin_constant_p(size)) {
/*
@@ -605,9 +632,10 @@ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size,
* (The SIZE_MAX test is to optimize away checks where the buffer
* lengths are unknown.)
*/
- if ((p_size != SIZE_MAX && p_size < size) ||
- (q_size != SIZE_MAX && q_size < size))
- fortify_panic(func);
+ if (p_size != SIZE_MAX && p_size < size)
+ fortify_panic(func, FORTIFY_WRITE);
+ else if (q_size != SIZE_MAX && q_size < size)
+ fortify_panic(func, FORTIFY_READ);
/*
* Warn when writing beyond destination field size.
@@ -640,7 +668,7 @@ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size,
const size_t __q_size_field = (q_size_field); \
WARN_ONCE(fortify_memcpy_chk(__fortify_size, __p_size, \
__q_size, __p_size_field, \
- __q_size_field, #op), \
+ __q_size_field, FORTIFY_FUNC_ ##op), \
#op ": detected field-spanning write (size %zu) of single %s (size %zu)\n", \
__fortify_size, \
"field \"" #p "\" at " __FILE__ ":" __stringify(__LINE__), \
@@ -707,7 +735,7 @@ __FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size)
if (__compiletime_lessthan(p_size, size))
__read_overflow();
if (p_size < size)
- fortify_panic(__func__);
+ fortify_panic(FORTIFY_FUNC_memscan, FORTIFY_READ);
return __real_memscan(p, c, size);
}
@@ -724,7 +752,7 @@ int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t
__read_overflow2();
}
if (p_size < size || q_size < size)
- fortify_panic(__func__);
+ fortify_panic(FORTIFY_FUNC_memcmp, FORTIFY_READ);
return __underlying_memcmp(p, q, size);
}
@@ -736,7 +764,7 @@ void *memchr(const void * const POS0 p, int c, __kernel_size_t size)
if (__compiletime_lessthan(p_size, size))
__read_overflow();
if (p_size < size)
- fortify_panic(__func__);
+ fortify_panic(FORTIFY_FUNC_memchr, FORTIFY_READ);
return __underlying_memchr(p, c, size);
}
@@ -748,7 +776,7 @@ __FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size)
if (__compiletime_lessthan(p_size, size))
__read_overflow();
if (p_size < size)
- fortify_panic(__func__);
+ fortify_panic(FORTIFY_FUNC_memchr_inv, FORTIFY_READ);
return __real_memchr_inv(p, c, size);
}
@@ -761,7 +789,7 @@ __FORTIFY_INLINE void *kmemdup(const void * const POS0 p, size_t size, gfp_t gfp
if (__compiletime_lessthan(p_size, size))
__read_overflow();
if (p_size < size)
- fortify_panic(__func__);
+ fortify_panic(FORTIFY_FUNC_kmemdup, FORTIFY_READ);
return __real_kmemdup(p, size, gfp);
}
@@ -798,7 +826,7 @@ char *strcpy(char * const POS p, const char * const POS q)
__write_overflow();
/* Run-time check for dynamic size overflow. */
if (p_size < size)
- fortify_panic(__func__);
+ fortify_panic(FORTIFY_FUNC_strcpy, FORTIFY_WRITE);
__underlying_memcpy(p, q, size);
return p;
}
diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index 230020a2e076..631c50657096 100644
--- a/lib/string_helpers.c
+++ b/lib/string_helpers.c
@@ -1021,10 +1021,74 @@ EXPORT_SYMBOL(__read_overflow2_field);
void __write_overflow_field(size_t avail, size_t wanted) { }
EXPORT_SYMBOL(__write_overflow_field);
-void fortify_panic(const char *name)
+void __fortify_report(u8 reason)
{
- pr_emerg("detected buffer overflow in %s\n", name);
+ const char *name;
+ const bool write = !!(reason & 0x1);
+
+ switch (reason >> 1) {
+ case FORTIFY_FUNC_strncpy:
+ name = "strncpy";
+ break;
+ case FORTIFY_FUNC_strnlen:
+ name = "strnlen";
+ break;
+ case FORTIFY_FUNC_strlen:
+ name = "strlen";
+ break;
+ case FORTIFY_FUNC_strlcpy:
+ name = "strlcpy";
+ break;
+ case FORTIFY_FUNC_strscpy:
+ name = "strscpy";
+ break;
+ case FORTIFY_FUNC_strlcat:
+ name = "strlcat";
+ break;
+ case FORTIFY_FUNC_strcat:
+ name = "strcat";
+ break;
+ case FORTIFY_FUNC_strncat:
+ name = "strncat";
+ break;
+ case FORTIFY_FUNC_memset:
+ name = "memset";
+ break;
+ case FORTIFY_FUNC_memcpy:
+ name = "memcpy";
+ break;
+ case FORTIFY_FUNC_memmove:
+ name = "memmove";
+ break;
+ case FORTIFY_FUNC_memscan:
+ name = "memscan";
+ break;
+ case FORTIFY_FUNC_memcmp:
+ name = "memcmp";
+ break;
+ case FORTIFY_FUNC_memchr:
+ name = "memchr";
+ break;
+ case FORTIFY_FUNC_memchr_inv:
+ name = "memchr_inv";
+ break;
+ case FORTIFY_FUNC_kmemdup:
+ name = "kmemdup";
+ break;
+ case FORTIFY_FUNC_strcpy:
+ name = "strcpy";
+ break;
+ default:
+ name = "unknown";
+ }
+ WARN(1, "%s: detected buffer %s overflow\n", name, write ? "write" : "read");
+}
+EXPORT_SYMBOL(__fortify_report);
+
+void __fortify_panic(const u8 reason)
+{
+ __fortify_report(reason);
BUG();
}
-EXPORT_SYMBOL(fortify_panic);
+EXPORT_SYMBOL(__fortify_panic);
#endif /* CONFIG_FORTIFY_SOURCE */
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index f937be1afe65..2d0a67ce1c51 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -197,6 +197,7 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
* attribute isn't provided in ELF data. Keep 'em sorted.
*/
static const char * const global_noreturns[] = {
+ "__fortify_panic",
"__invalid_creds",
"__module_put_and_kthread_exit",
"__reiserfs_panic",
@@ -208,7 +209,6 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
"do_group_exit",
"do_task_dead",
"ex_handler_msr_mce",
- "fortify_panic",
"kthread_complete_and_exit",
"kthread_exit",
"kunit_try_catch_throw",
--
2.34.1
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