linux-kernel - [PATCH 10/10] string.h: Validate memtostr*()/strtomem*() arguments more carefully

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Message-Id: <20250207010022.749952-10-kees@kernel.org>
Date: Thu,  6 Feb 2025 17:00:19 -0800
From: Kees Cook <kees@...nel.org>
To: Andy Shevchenko <andy@...nel.org>
Cc: Kees Cook <kees@...nel.org>,
	linux-hardening@...r.kernel.org,
	Sathya Prakash <sathya.prakash@...adcom.com>,
	Sreekanth Reddy <sreekanth.reddy@...adcom.com>,
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	Sumit Saxena <sumit.saxena@...adcom.com>,
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	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Nilesh Javali <njavali@...vell.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
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Subject: [PATCH 10/10] string.h: Validate memtostr*()/strtomem*() arguments more carefully

Since these functions handle moving between C strings and non-C strings,
they should check for the appropriate presence/lack of the nonstring
attribute on arguments.

Signed-off-by: Kees Cook <kees@...nel.org>
---
Cc: Andy Shevchenko <andy@...nel.org>
Cc: linux-hardening@...r.kernel.org
---
 include/linux/string.h | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/include/linux/string.h b/include/linux/string.h
index fc5ae145bd78..26491a2f8010 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -412,8 +412,10 @@ void memcpy_and_pad(void *dest, size_t dest_len, const void *src, size_t count,
  */
 #define strtomem_pad(dest, src, pad)	do {				\
 	const size_t _dest_len = __must_be_byte_array(dest) +		\
+				 __must_be_noncstr(dest) +		\
 				 ARRAY_SIZE(dest);			\
-	const size_t _src_len = __builtin_object_size(src, 1);		\
+	const size_t _src_len = __must_be_cstr(src) +			\
+				__builtin_object_size(src, 1);		\
 									\
 	BUILD_BUG_ON(!__builtin_constant_p(_dest_len) ||		\
 		     _dest_len == (size_t)-1);				\
@@ -436,8 +438,10 @@ void memcpy_and_pad(void *dest, size_t dest_len, const void *src, size_t count,
  */
 #define strtomem(dest, src)	do {					\
 	const size_t _dest_len = __must_be_byte_array(dest) +		\
+				 __must_be_noncstr(dest) +		\
 				 ARRAY_SIZE(dest);			\
-	const size_t _src_len = __builtin_object_size(src, 1);		\
+	const size_t _src_len = __must_be_cstr(src) +			\
+				__builtin_object_size(src, 1);		\
 									\
 	BUILD_BUG_ON(!__builtin_constant_p(_dest_len) ||		\
 		     _dest_len == (size_t)-1);				\
@@ -456,8 +460,10 @@ void memcpy_and_pad(void *dest, size_t dest_len, const void *src, size_t count,
  */
 #define memtostr(dest, src)	do {					\
 	const size_t _dest_len = __must_be_byte_array(dest) +		\
+				 __must_be_cstr(dest) +			\
 				 ARRAY_SIZE(dest);			\
-	const size_t _src_len = __builtin_object_size(src, 1);		\
+	const size_t _src_len = __must_be_noncstr(src) +		\
+				__builtin_object_size(src, 1);		\
 	const size_t _src_chars = strnlen(src, _src_len);		\
 	const size_t _copy_len = min(_dest_len - 1, _src_chars);	\
 									\
@@ -482,8 +488,10 @@ void memcpy_and_pad(void *dest, size_t dest_len, const void *src, size_t count,
  */
 #define memtostr_pad(dest, src)		do {				\
 	const size_t _dest_len = __must_be_byte_array(dest) +		\
+				 __must_be_cstr(dest) +			\
 				 ARRAY_SIZE(dest);			\
-	const size_t _src_len = __builtin_object_size(src, 1);		\
+	const size_t _src_len = __must_be_noncstr(src) +		\
+				__builtin_object_size(src, 1);		\
 	const size_t _src_chars = strnlen(src, _src_len);		\
 	const size_t _copy_len = min(_dest_len - 1, _src_chars);	\
 									\
-- 
2.34.1