Merge from NetBSD:

Fix a problem in previous: we can't blindly assume that we have
wincnt entries available at the offset the file has been found. If the dos
directory entry is not preceded by appropriate number of long name
entries (happens e.g. when the filesystem is corrupted, or when
the filename complies to DOS rules and doesn't use any long name entry),
we would overwrite random directory entries.

There are still some problems, the whole thing has to be revisited and solved
right.

Submitted by:	Xin LI

1 files changed, 18 insertions, 3 deletions

diff --git a/sys/fs/msdosfs/msdosfs_lookup.c b/sys/fs/msdosfs/msdosfs_lookup.c
index 1492098..446f0b2 100644
--- a/sys/fs/msdosfs/msdosfs_lookup.c
+++ b/sys/fs/msdosfs/msdosfs_lookup.c
@@ -114,7 +114,7 @@ msdosfs_lookup(ap)
 	int unlen;
 
 	int wincnt = 1;
-	int chksum = -1;
+	int chksum = -1, chksum_ok;
 	int olddos = 1;
 	cnp->cn_flags &= ~PDIRUNLOCK;
 
@@ -283,7 +283,8 @@ msdosfs_lookup(ap)
 				/*
 				 * Check for a checksum or name match
 				 */
-				if (chksum != winChksum(dep->deName)
+				chksum_ok = (chksum == winChksum(dep->deName));
+				if (!chksum_ok
 				    && (!olddos || bcmp(dosfilename, dep->deName, 11))) {
 					chksum = -1;
 					continue;
@@ -298,7 +299,21 @@ msdosfs_lookup(ap)
 				 * this lookup.
 				 */
 				dp->de_fndoffset = diroff;
-				dp->de_fndcnt = wincnt - 1;
+				if (chksum_ok && nameiop == RENAME) {
+					/*
+					 * Target had correct long name
+					 * directory entries, reuse them
+					 * as needed.
+					 */
+					dp->de_fndcnt = wincnt - 1;
+				} else {
+					/*
+					 * Long name directory entries
+					 * not present or corrupt, can only
+					 * reuse dos directory entry.
+					 */
+					dp->de_fndcnt = 0;
+				}
 
 				goto found;
 			}