From: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Subject: 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@xxxxxxxxxxxxx: move kasan check under the condition] Link: http://lkml.kernel.org/r/1462869209-21096-1-git-send-email-aryabinin@xxxxxxxxxxxxx Link: http://lkml.kernel.org/r/1462538722-1574-4-git-send-email-aryabinin@xxxxxxxxxxxxx Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> Cc: Alexander Potapenko <glider@xxxxxxxxxx> Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/x86/include/asm/uaccess.h | 5 +++++ arch/x86/include/asm/uaccess_64.h | 7 +++++++ lib/strncpy_from_user.c | 2 ++ 3 files changed, 14 insertions(+) diff -puN arch/x86/include/asm/uaccess.h~x86-kasan-instrument-user-memory-access-api arch/x86/include/asm/uaccess.h --- a/arch/x86/include/asm/uaccess.h~x86-kasan-instrument-user-memory-access-api +++ a/arch/x86/include/asm/uaccess.h @@ -5,6 +5,7 @@ */ #include <linux/errno.h> #include <linux/compiler.h> +#include <linux/kasan-checks.h> #include <linux/thread_info.h> #include <linux/string.h> #include <asm/asm.h> @@ -721,6 +722,8 @@ copy_from_user(void *to, const void __us might_fault(); + kasan_check_write(to, n); + /* * While we would like to have the compiler do the checking for us * even in the non-constant size case, any false positives there are @@ -754,6 +757,8 @@ copy_to_user(void __user *to, const void { int sz = __compiletime_object_size(from); + kasan_check_read(from, n); + might_fault(); /* See the comment in copy_from_user() above. */ diff -puN arch/x86/include/asm/uaccess_64.h~x86-kasan-instrument-user-memory-access-api arch/x86/include/asm/uaccess_64.h --- a/arch/x86/include/asm/uaccess_64.h~x86-kasan-instrument-user-memory-access-api +++ a/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, con 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); } diff -puN lib/strncpy_from_user.c~x86-kasan-instrument-user-memory-access-api lib/strncpy_from_user.c --- a/lib/strncpy_from_user.c~x86-kasan-instrument-user-memory-access-api +++ a/lib/strncpy_from_user.c @@ -1,5 +1,6 @@ #include <linux/compiler.h> #include <linux/export.h> +#include <linux/kasan-checks.h> #include <linux/uaccess.h> #include <linux/kernel.h> #include <linux/errno.h> @@ -109,6 +110,7 @@ long strncpy_from_user(char *dst, const unsigned long max = max_addr - src_addr; long retval; + kasan_check_write(dst, count); user_access_begin(); retval = do_strncpy_from_user(dst, src, count, max); user_access_end(); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
