linux-kernel - [PATCH v2 1/3] kasan: move checks to do_strncpy_from

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Message-Id: <20241013130211.3067196-2-snovitoll@gmail.com>
Date: Sun, 13 Oct 2024 18:02:09 +0500
From: Sabyrzhan Tasbolatov <snovitoll@...il.com>
To: andreyknvl@...il.com
Cc: akpm@...ux-foundation.org,
	dvyukov@...gle.com,
	glider@...gle.com,
	kasan-dev@...glegroups.com,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	ryabinin.a.a@...il.com,
	snovitoll@...il.com,
	vincenzo.frascino@....com,
	elver@...gle.com,
	corbet@....net,
	alexs@...nel.org,
	siyanteng@...ngson.cn,
	2023002089@...k.tyut.edu.cn,
	workflows@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: [PATCH v2 1/3] kasan: move checks to do_strncpy_from_user

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")
Signed-off-by: Sabyrzhan Tasbolatov <snovitoll@...il.com>
---
 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