[PATCH v3 22/22] x86/int3: Ensure that poke_int3_handler() is not sanitized

Peter Zijlstra
2020-02-19T15:14:24Z

In order to ensure poke_int3_handler() is completely self contained --
we call this while we're modifying other text, imagine the fun of
hitting another INT3 -- ensure that everything is without sanitize
crud.

Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/kernel/alternative.c | 4 ++--
arch/x86/kernel/traps.c | 2 +-
include/linux/compiler-clang.h | 7 +++++++
include/linux/compiler-gcc.h | 6 ++++++
include/linux/compiler.h | 5 +++++
include/linux/compiler_attributes.h | 1 +
lib/bsearch.c | 2 +-
7 files changed, 23 insertions(+), 4 deletions(-)

--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -979,7 +979,7 @@ static __always_inline void *text_poke_a
return _stext + tp->rel_addr;
}

-static int notrace patch_cmp(const void *key, const void *elt)
+static int notrace __no_sanitize patch_cmp(const void *key, const void *elt)
{
struct text_poke_loc *tp = (struct text_poke_loc *) elt;

@@ -991,7 +991,7 @@ static int notrace patch_cmp(const void
}
NOKPROBE_SYMBOL(patch_cmp);

-int notrace poke_int3_handler(struct pt_regs *regs)
+int notrace __no_sanitize poke_int3_handler(struct pt_regs *regs)
{
struct bp_patching_desc *desc;
struct text_poke_loc *tp;
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -496,7 +496,7 @@ dotraplinkage void do_general_protection
}
NOKPROBE_SYMBOL(do_general_protection);

-dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
+dotraplinkage void notrace __no_sanitize do_int3(struct pt_regs *regs, long error_code)
{
if (poke_int3_handler(regs))
return;
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -24,6 +24,13 @@
#define __no_sanitize_address
#endif

+#if __has_feature(undefined_sanitizer)
+#define __no_sanitize_undefined \
+ __atribute__((no_sanitize("undefined")))
+#else
+#define __no_sanitize_undefined
+#endif
+
/*
* Not all versions of clang implement the the type-generic versions
* of the builtin overflow checkers. Fortunately, clang implements
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -145,6 +145,12 @@
#define __no_sanitize_address
#endif

+#if __has_attribute(__no_sanitize_undefined__)
+#define __no_sanitize_undefined __attribute__((no_sanitize_undefined))
+#else
+#define __no_sanitize_undefined
+#endif
+
#if GCC_VERSION >= 50100
#define COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW 1
#endif
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -199,6 +199,7 @@ void __read_once_size(const volatile voi
__READ_ONCE_SIZE;
}

+#define __no_kasan __no_sanitize_address
#ifdef CONFIG_KASAN
/*
* We can't declare function 'inline' because __no_sanitize_address confilcts
@@ -274,6 +275,10 @@ static __always_inline void __write_once
*/
#define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)

+#define __no_ubsan __no_sanitize_undefined
+
+#define __no_sanitize __no_kasan __no_ubsan
+
static __no_kasan_or_inline
unsigned long read_word_at_a_time(const void *addr)
{
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -41,6 +41,7 @@
# define __GCC4_has_attribute___nonstring__ 0
# define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
# define __GCC4_has_attribute___fallthrough__ 0
+# define __GCC4_has_attribute___no_sanitize_undefined__ (__GNUC_MINOR__ >= 9)
#endif

/*
--- a/lib/bsearch.c
+++ b/lib/bsearch.c
@@ -28,7 +28,7 @@
* the key and elements in the array are of the same type, you can use
* the same comparison function for both sort() and bsearch().
*/
-void *bsearch(const void *key, const void *base, size_t num, size_t size,
+void __no_sanitize *bsearch(const void *key, const void *base, size_t num, size_t size,
cmp_func_t cmp)
{
const char *pivot;