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>
diff --git a/fs/dcache.c b/fs/dcache.c
index 265e0ce..ca02c13 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2833,9 +2833,9 @@
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--) {
