On Fri, May 6, 2016 at 2:45 PM, Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> 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 <dvyukov@xxxxxxxxxx> Thanks! > Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx> > Cc: Alexander Potapenko <glider@xxxxxxxxxx> > Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > Cc: x86@xxxxxxxxxx > --- > 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 <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> > @@ -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 <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); > } > > 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 <linux/compiler.h> > #include <linux/export.h> > +#include <linux/kasan-checks.h> > #include <linux/uaccess.h> > #include <linux/kernel.h> > #include <linux/errno.h> > @@ -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 > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>