lib: Clarify the return value of strnlen_user() (226a07ef) · Commits · 戴 / test

strnlen_user() can return a number in a range 0 to count + sizeof(unsigned long) - 1. Clarify the comment at the top of the function so that users don't think the function returns at most count+1. Signed-off-by:

Jan Kara <jack@suse.cz> [ Also added commentary about preferably not using this function ] Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

lib/strnlen_user.c

+8 −1

Original line number	Diff line number	Diff line
		@@ -90,8 +90,15 @@ static inline long do_strnlen_user(const char __user *src, unsigned long count,
		* Get the size of a NUL-terminated string in user space.
		*
		* Returns the size of the string INCLUDING the terminating NUL.
		* If the string is too long, returns 'count+1'.
		* If the string is too long, returns a number larger than @count. User
		* has to check the return value against "> count".
		* On exception (or invalid count), returns 0.
		*
		* NOTE! You should basically never use this function. There is
		* almost never any valid case for using the length of a user space
		* string, since the string can be changed at any time by other
		* threads. Use "strncpy_from_user()" instead to get a stable copy
		* of the string.
		*/
		long strnlen_user(const char __user *str, long count)
		{

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