[PATCH v2] uml: Replace strlcpy with strscpy

From: Azeem Shaikh <azeemshaikh38@gmail.com>
To: Maxim Krasnyansky <maxk@qti.qualcomm.com>,
	Richard Weinberger <richard@nod.at>,
	Anton Ivanov <anton.ivanov@cambridgegreys.com>,
	Johannes Berg <johannes@sipsolutions.net>
Cc: linux-hardening@vger.kernel.org,
	Azeem Shaikh <azeemshaikh38@gmail.com>,
	linux-kernel@vger.kernel.org, linux-um@lists.infradead.org,
	"Jason A. Donenfeld" <Jason@zx2c4.com>,
	kernel test robot <lkp@intel.com>
Subject: [PATCH v2] uml: Replace strlcpy with strscpy
Date: Tue,  6 Jun 2023 18:24:09 +0000	[thread overview]
Message-ID: <20230606182410.3976487-1-azeemshaikh38@gmail.com> (raw)

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().
No return values were used, so direct replacement is safe.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202305311135.zGMT1gYR-lkp@intel.com/
---
v1: https://lore.kernel.org/all/20230530164004.986750-1-azeemshaikh38@gmail.com/

Changes from v1 - added strscpy declaration. v1 does not build.

 arch/um/include/shared/user.h          | 1 +
 arch/um/os-Linux/drivers/tuntap_user.c | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/um/include/shared/user.h b/arch/um/include/shared/user.h
index bda66e5a9d4e..0347a190429c 100644
--- a/arch/um/include/shared/user.h
+++ b/arch/um/include/shared/user.h
@@ -52,6 +52,7 @@ static inline int printk(const char *fmt, ...)
 extern int in_aton(char *str);
 extern size_t strlcpy(char *, const char *, size_t);
 extern size_t strlcat(char *, const char *, size_t);
+extern size_t strscpy(char *, const char *, size_t);
 
 /* Copied from linux/compiler-gcc.h since we can't include it directly */
 #define barrier() __asm__ __volatile__("": : :"memory")
diff --git a/arch/um/os-Linux/drivers/tuntap_user.c b/arch/um/os-Linux/drivers/tuntap_user.c
index 53eb3d508645..2284e9c1cbbb 100644
--- a/arch/um/os-Linux/drivers/tuntap_user.c
+++ b/arch/um/os-Linux/drivers/tuntap_user.c
@@ -146,7 +146,7 @@ static int tuntap_open(void *data)
 		}
 		memset(&ifr, 0, sizeof(ifr));
 		ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
-		strlcpy(ifr.ifr_name, pri->dev_name, sizeof(ifr.ifr_name));
+		strscpy(ifr.ifr_name, pri->dev_name, sizeof(ifr.ifr_name));
 		if (ioctl(pri->fd, TUNSETIFF, &ifr) < 0) {
 			err = -errno;
 			printk(UM_KERN_ERR "TUNSETIFF failed, errno = %d\n",
-- 
2.41.0.rc0.172.g3f132b7071-goog

