[PATCH RESEND v3 1/3] kasan: move checks to do_strncpy_from_user

[Sabyrzhan Tasbolatov]

Since in the commit 2865baf54077("x86: support user address masking instead
of non-speculative conditional") do_strncpy_from_user() is called from
multiple places, we should sanitize the kernel *dst memory and size
which were done in strncpy_from_user() previously.

Fixes: 2865baf54077 ("x86: support user address masking instead of non-speculative conditional")
Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@xxxxxxxxx>
---
 lib/strncpy_from_user.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index 989a12a6787..f36ad821176 100644
--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -31,6 +31,9 @@ static __always_inline long do_strncpy_from_user(char *dst, const char __user *s
 	const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
 	unsigned long res = 0;
 
+	kasan_check_write(dst, count);
+	check_object_size(dst, count, false);
+
 	if (IS_UNALIGNED(src, dst))
 		goto byte_at_a_time;
 
@@ -142,8 +145,6 @@ long strncpy_from_user(char *dst, const char __user *src, long count)
 		if (max > count)
 			max = count;
 
-		kasan_check_write(dst, count);
-		check_object_size(dst, count, false);
 		if (user_read_access_begin(src, max)) {
 			retval = do_strncpy_from_user(dst, src, count, max);
 			user_read_access_end();
-- 
2.34.1