x86/kasan: instrument user memory access API

Exchange between user and kernel memory is coded in assembly language.
Which means that such accesses won't be spotted by KASAN as a compiler
instruments only C code.

Add explicit KASAN checks to user memory access API to ensure that
userspace writes to (or reads from) a valid kernel memory.

Note: Unlike others strncpy_from_user() is written mostly in C and KASAN
sees memory accesses in it.  However, it makes sense to add explicit
check for all @count bytes that *potentially* could be written to the
kernel.

[aryabinin@virtuozzo.com: move kasan check under the condition]
  Link: http://lkml.kernel.org/r/1462869209-21096-1-git-send-email-aryabinin@virtuozzo.com
Link: http://lkml.kernel.org/r/1462538722-1574-4-git-send-email-aryabinin@virtuozzo.com
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index 307698688fa1..2eac2aa3e37f 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -7,6 +7,7 @@
 #include <linux/compiler.h>
 #include <linux/errno.h>
 #include <linux/lockdep.h>
+#include <linux/kasan-checks.h>
 #include <asm/alternative.h>
 #include <asm/cpufeatures.h>
 #include <asm/page.h>
@@ -109,6 +110,7 @@ static __always_inline __must_check
 int __copy_from_user(void *dst, const void __user *src, unsigned size)
 {
 	might_fault();
+	kasan_check_write(dst, size);
 	return __copy_from_user_nocheck(dst, src, size);
 }
 
@@ -175,6 +177,7 @@ static __always_inline __must_check
 int __copy_to_user(void __user *dst, const void *src, unsigned size)
 {
 	might_fault();
+	kasan_check_read(src, size);
 	return __copy_to_user_nocheck(dst, src, size);
 }
 
@@ -242,12 +245,14 @@ int __copy_in_user(void __user *dst, const void __user *src, unsigned size)
 static __must_check __always_inline int
 __copy_from_user_inatomic(void *dst, const void __user *src, unsigned size)
 {
+	kasan_check_write(dst, size);
 	return __copy_from_user_nocheck(dst, src, size);
 }
 
 static __must_check __always_inline int
 __copy_to_user_inatomic(void __user *dst, const void *src, unsigned size)
 {
+	kasan_check_read(src, size);
 	return __copy_to_user_nocheck(dst, src, size);
 }
 
@@ -258,6 +263,7 @@ static inline int
 __copy_from_user_nocache(void *dst, const void __user *src, unsigned size)
 {
 	might_fault();
+	kasan_check_write(dst, size);
 	return __copy_user_nocache(dst, src, size, 1);
 }
 
@@ -265,6 +271,7 @@ static inline int
 __copy_from_user_inatomic_nocache(void *dst, const void __user *src,
 				  unsigned size)
 {
+	kasan_check_write(dst, size);
 	return __copy_user_nocache(dst, src, size, 0);
 }