Patch "get_rock_ridge_filename(): handle malformed NM entries" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

get_rock_ridge_filename(): handle malformed NM entries

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
get_rock_ridge_filename-handle-malformed-nm-entries.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Al Viro <[email protected]>
Date: Thu, 5 May 2016 16:25:35 -0400
Subject: get_rock_ridge_filename(): handle malformed NM entries

From: Al Viro <[email protected]>

commit 99d825822eade8d827a1817357cbf3f889a552d6 upstream.

Payloads of NM entries are not supposed to contain NUL. When we run into such, only the part prior to the first NUL goes into the concatenation (i.e. the directory entry name being encoded by a bunch of NM entries). We do stop when the amount collected so far + the claimed amount in the current NM entry exceed 254. So far, so good, but what we return as the total length is the sum of *claimed* sizes, not the actual amount collected. And that can grow pretty large - not unlimited, since you'd need to put CE entries in between to be able to get more than the maximum that could be contained in one isofs directory entry / continuation chunk and we are stop once we'd encountered 32 CEs, but you can get about 8Kb easily. And that's what will be passed to readdir callback as the name length. 8Kb __copy_to_user() from a buffer allocated by __get_free_page()

---
 fs/isofs/rock.c |   13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

@@ -203,6 +203,8 @@ int get_rock_ridge_filename(struct iso_d
 	int retnamlen = 0;
 	int truncate = 0;
 	int ret = 0;
+	char *p;
+	int len;
 
 	if (!ISOFS_SB(inode->i_sb)->s_rock)
 		return 0;

@@ -267,12 +269,17 @@ repeat:
 					rr->u.NM.flags);
 				break;
 			}
-			if ((strlen(retname) + rr->len - 5) >= 254) {
+			len = rr->len - 5;
+			if (retnamlen + len >= 254) {
 				truncate = 1;
 				break;
 			}
-			strncat(retname, rr->u.NM.name, rr->len - 5);
-			retnamlen += rr->len - 5;
+			p = memchr(rr->u.NM.name, '\0', len);
+			if (unlikely(p))
+				len = p - rr->u.NM.name;
+			memcpy(retname + retnamlen, rr->u.NM.name, len);
+			retnamlen += len;
+			retname[retnamlen] = '\0';
 			break;
 		case SIG('R', 'E'):
 			kfree(rs.buffer);

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/get_rock_ridge_filename-handle-malformed-nm-entries.patch queue-4.4/atomic_open-fix-the-handling-of-create_error.patch