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Date: Tue, 19 Feb 2019 10:23:07 +1100
From: "Tobin C. Harding" <tobin@...nel.org>
To: Kees Cook <keescook@...omium.org>
Cc: "Tobin C. Harding" <tobin@...nel.org>,
Shuah Khan <shuah@...nel.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
kernel-hardening@...ts.openwall.com,
linux-kernel@...r.kernel.org
Subject: [PATCH 5/6] lib: Fix function documentation for strncpy_from_user
Current function documentation for strncpy_from_user() is incorrect. If
@count (size of destination buffer) is less than the length of the user
string the function does _not_ return @count but rather returns -EFAULT.
Document correctly the function return value, also add note that string
may be left non-null terminated.
Signed-off-by: Tobin C. Harding <tobin@...nel.org>
---
lib/strncpy_from_user.c | 17 +++++++----------
1 file changed, 7 insertions(+), 10 deletions(-)
diff --git a/lib/strncpy_from_user.c b/lib/strncpy_from_user.c
index 58eacd41526c..11fe9a4a00fd 100644
--- a/lib/strncpy_from_user.c
+++ b/lib/strncpy_from_user.c
@@ -82,22 +82,19 @@ static inline long do_strncpy_from_user(char *dst, const char __user *src, long
}
/**
- * strncpy_from_user: - Copy a NUL terminated string from userspace.
+ * strncpy_from_user() - Copy a NUL terminated string from userspace.
* @dst: Destination address, in kernel space. This buffer must be at
* least @count bytes long.
* @src: Source address, in user space.
- * @count: Maximum number of bytes to copy, including the trailing NUL.
+ * @count: Maximum number of bytes to copy, including the trailing %NUL.
*
* Copies a NUL-terminated string from userspace to kernel space.
*
- * On success, returns the length of the string (not including the trailing
- * NUL).
- *
- * If access to userspace fails, returns -EFAULT (some data may have been
- * copied).
- *
- * If @count is smaller than the length of the string, copies @count bytes
- * and returns @count.
+ * Return: If access to userspace fails, returns -EFAULT. Otherwise,
+ * return the number of characters copied excluding the trailing
+ * %NUL, if the length of the user string exceeds @count return
+ * -EFAULT (in which case @dst will be left without a %NUL
+ * terminator).
*/
long strncpy_from_user(char *dst, const char __user *src, long count)
{
--
2.20.1
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