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Code Issues Releases Wiki Activity

lib: Clarify the return value of strnlen_user() 

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>
This commit is contained in:
Jan Kara 2015-06-03 15:50:35 +02:00 committed by Linus Torvalds
parent 8cd9234c64
commit 226a07ef0a
1 changed files with 8 additions and 1 deletions
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9
lib/strnlen_user.c
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@ -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)
{