make prepend_name() work correctly when called with negative *buflen

In all callchains leading to prepend_name(), the value left in *buflen
is eventually discarded unused if prepend_name() has returned a negative.
So we are free to do what prepend() does, and subtract from *buflen
*before* checking for underflow (which turns into checking the sign
of subtraction result, of course).

Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2014-03-23 00:28:40 -04:00
parent 99aea68134
commit e825196d48
1 changed files with 2 additions and 2 deletions

View File

@ -2833,9 +2833,9 @@ static int prepend_name(char **buffer, int *buflen, struct qstr *name)
u32 dlen = ACCESS_ONCE(name->len);
char *p;
if (*buflen < dlen + 1)
return -ENAMETOOLONG;
*buflen -= dlen + 1;
if (*buflen < 0)
return -ENAMETOOLONG;
p = *buffer -= dlen + 1;
*p++ = '/';
while (dlen--) {