Commit 76624175 authored Feb 07, 2017 by Mark Rutland Committed by Will Deacon Feb 08, 2017

arm64: uaccess: consistently check object sizes



Currently in arm64's copy_{to,from}_user, we only check the
source/destination object size if access_ok() tells us the user access
is permissible.

However, in copy_from_user() we'll subsequently zero any remainder on
the destination object. If we failed the access_ok() check, that applies
to the whole object size, which we didn't check.

To ensure that we catch that case, this patch hoists check_object_size()
to the start of copy_from_user(), matching __copy_from_user() and
__copy_to_user(). To make all of our uaccess copy primitives consistent,
the same is done to copy_to_user().

Cc: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

parent 21bdbb71

arch/arm64/include/asm/uaccess.h

+2 −2

Original line number	Diff line number	Diff line
		@@ -379,9 +379,9 @@ static inline unsigned long __must_check copy_from_user(void *to, const void __u
		{
		unsigned long res = n;
		kasan_check_write(to, n);
		check_object_size(to, n, false);

		if (access_ok(VERIFY_READ, from, n)) {
		check_object_size(to, n, false);
		res = __arch_copy_from_user(to, from, n);
		}
		if (unlikely(res))
		@@ -392,9 +392,9 @@ static inline unsigned long __must_check copy_from_user(void *to, const void __u
		static inline unsigned long __must_check copy_to_user(void __user to, const void from, unsigned long n)
		{
		kasan_check_read(from, n);
		check_object_size(from, n, true);

		if (access_ok(VERIFY_WRITE, to, n)) {
		check_object_size(from, n, true);
		n = __arch_copy_to_user(to, from, n);
		}
		return n;