cifs: Fix cifs_limit_bvec_subset() to correctly check the maxmimum size

Fix cifs_limit_bvec_subset() so that it limits the span to the maximum
specified and won't return with a size greater than max_size.

Fixes: d08089f ("cifs: Change the I/O paths to use an iterator rather than a page list")
Cc: [email protected] # 6.3
Reported-by: Shyam Prasad N <[email protected]>
Reviewed-by: Shyam Prasad N <[email protected]>
Signed-off-by: David Howells <[email protected]>
cc: Steve French <[email protected]>
cc: Rohith Surabattula <[email protected]>
cc: Paulo Alcantara <[email protected]>
cc: Tom Talpey <[email protected]>
cc: Jeff Layton <[email protected]>
cc: [email protected]
cc: [email protected]
Signed-off-by: Steve French <[email protected]>

Author: dhowells

fs/cifs/file.c

@@ -3353,9 +3353,10 @@ static size_t cifs_limit_bvec_subset(const struct iov_iter *iter, size_t max_siz
 	while (n && ix < nbv) {
 		len = min3(n, bvecs[ix].bv_len - skip, max_size);
 		span += len;
+		max_size -= len;
 		nsegs++;
 		ix++;
-		if (span >= max_size || nsegs >= max_segs)
+		if (max_size == 0 || nsegs >= max_segs)
 			break;
 		skip = 0;
 		n -= len;