Re: [PATCH 4/4] x86/kasan: Instrument user memory access API

2016-05-08 Thread Ingo Molnar 

* Andrey Ryabinin  wrote:

> 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.
> 
> Signed-off-by: Andrey Ryabinin 
> Cc: Alexander Potapenko 
> Cc: Dmitry Vyukov 
> Cc: x...@kernel.org
> ---
>  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 --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
> index 3384032..e3472b0 100644
> --- a/lib/strncpy_from_user.c
> +++ b/lib/strncpy_from_user.c
> @@ -1,5 +1,6 @@
>  #include 
>  #include 
> +#include 
>  #include 
>  #include 
>  #include 
> @@ -103,6 +104,7 @@ long strncpy_from_user(char *dst, const char __user *src, 
> long count)
>   if (unlikely(count <= 0))
>   return 0;
>  
> + kasan_check_write(dst, count);
>   max_addr = user_addr_max();
>   src_addr = (unsigned long)src;
>   if (likely(src_addr < max_addr)) {

Please do the check inside the condition, before the user_access_begin(), 
because 
where you've put the check we might still fail and not do a user copy and 
-EFAULT 
out.

With that fixed:

Reviewed-by: Ingo Molnar 

Thanks,

Ingo

Re: [PATCH 4/4] x86/kasan: Instrument user memory access API

2016-05-08 Thread Dmitry Vyukov 
On Fri, May 6, 2016 at 2:45 PM, Andrey Ryabinin  wrote:
> 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.


Reviewed-by: Dmitry Vyukov 

Thanks!


> Signed-off-by: Andrey Ryabinin 
> Cc: Alexander Potapenko 
> Cc: Dmitry Vyukov 
> Cc: x...@kernel.org
> ---
>  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 --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
> index 0b17fad..5dd6d18 100644
> --- a/arch/x86/include/asm/uaccess.h
> +++ b/arch/x86/include/asm/uaccess.h
> @@ -5,6 +5,7 @@
>   */
>  #include 
>  #include 
> +#include 
>  #include 
>  #include 
>  #include 
> @@ -732,6 +733,8 @@ copy_from_user(void *to, const void __user *from, 
> unsigned long n)
>
> 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
> @@ -765,6 +768,8 @@ copy_to_user(void __user *to, const void *from, unsigned 
> long n)
>  {
> int sz = __compiletime_object_size(from);
>
> +   kasan_check_read(from, n);
> +
> might_fault();
>
> /* See the comment in copy_from_user() above. */
> diff --git a/arch/x86/include/asm/uaccess_64.h 
> b/arch/x86/include/asm/uaccess_64.h
> index 3076986..2eac2aa 100644
> --- a/arch/x86/include/asm/uaccess_64.h
> +++ b/arch/x86/include/asm/uaccess_64.h
> @@ -7,6 +7,7 @@
>  #include 
>  #include 
>  #include 
> +#include 
>  #include 
>  #include 
>  #include 
> @@ -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);
>  }
>
> diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
> index 3384032..e3472b0 100644
> --- a/lib/strncpy_from_user.c
> +++ b/lib/strncpy_from_user.c
> @@ -1,5 +1,6 @@
>  #include 
>  #include 
> +#include 
>  #include 
>  #include 
>  #include 
> @@ -103,6 +104,7 @@ long strncpy_from_user(char *dst, const char __user *src, 
> long count)
> if (unlikely(count <= 0))
> return 0;
>
> +   kasan_check_write(dst, count);
> max_addr = user_addr_max();
> src_addr = (unsigned long)src;
> if (likely(src_addr < max_addr)) {
> --
> 2.7.3
>

[PATCH 4/4] x86/kasan: Instrument user memory access API

2016-05-06 Thread Andrey Ryabinin 
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.

Signed-off-by: Andrey Ryabinin 
Cc: Alexander Potapenko 
Cc: Dmitry Vyukov 
Cc: x...@kernel.org
---
 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 --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 0b17fad..5dd6d18 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -5,6 +5,7 @@
  */
 #include 
 #include 
+#include 
 #include 
 #include 
 #include 
@@ -732,6 +733,8 @@ copy_from_user(void *to, const void __user *from, unsigned 
long n)
 
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
@@ -765,6 +768,8 @@ copy_to_user(void __user *to, const void *from, unsigned 
long n)
 {
int sz = __compiletime_object_size(from);
 
+   kasan_check_read(from, n);
+
might_fault();
 
/* See the comment in copy_from_user() above. */
diff --git a/arch/x86/include/asm/uaccess_64.h 
b/arch/x86/include/asm/uaccess_64.h
index 3076986..2eac2aa 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -7,6 +7,7 @@
 #include 
 #include 
 #include 
+#include 
 #include 
 #include 
 #include 
@@ -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);
 }
 
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index 3384032..e3472b0 100644
--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -1,5 +1,6 @@
 #include 
 #include 
+#include 
 #include 
 #include 
 #include 
@@ -103,6 +104,7 @@ long strncpy_from_user(char *dst, const char __user *src, 
long count)
if (unlikely(count <= 0))
return 0;
 
+   kasan_check_write(dst, count);
max_addr = user_addr_max();
src_addr = (unsigned long)src;
if (likely(src_addr < max_addr)) {
-- 
2.7.3