[PATCH v4 27/27] x86/int3: Ensure that poke_int3_handler() is not sanitized

Peter Zijlstra
2020-02-21T13:50:26Z

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
instrumentation.

Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
---
arch/x86/kernel/alternative.c | 2 +-
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 +
6 files changed, 21 insertions(+), 2 deletions(-)

--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -990,7 +990,7 @@ static __always_inline int patch_cmp(con
return 0;
}

-int notrace poke_int3_handler(struct pt_regs *regs)
+notrace __no_sanitize int 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
@@ -502,7 +502,7 @@ dotraplinkage void do_general_protection
}
NOKPROBE_SYMBOL(do_general_protection);

-dotraplinkage notrace void do_int3(struct pt_regs *regs, long error_code)
+dotraplinkage notrace __no_sanitize void 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

/*