From: Andrew Deason <adeason@sinenomine.net>
Date: Wed, 22 Jun 2011 18:44:38 +0000 (-0500)
Subject: afs: Ensure afs_calc_inum yields nonzero ino
X-Git-Tag: upstream/1.6.2_pre2^2~192
X-Git-Url: https://git.michaelhowe.org/gitweb/?a=commitdiff_plain;h=e7ea7af6573cd03859b357387a3ee666e2a6ded5;p=packages%2Fo%2Fopenafs.git

afs: Ensure afs_calc_inum yields nonzero ino

afs_calc_inum can currently yield an inode of 0 if MD5-based inode
numbers are turned on. Some userspace applications (and for some
platforms, maybe even the kernel) make certain assumptions about the
inode number for a file; in particular for example, 'ls' will not
display a file with inode 0 in a normal directory listing.

So, read the md5 digest until we get a non-zero result. Fall back to
the non-md5 calculation if we still somehow end up with a 0.

While this case may at first glance seem to be extremely rare, in
practice it can occur, as the current calculation for volume
538313506, vnode 26178 does actually yield a 0.

Reviewed-on: http://gerrit.openafs.org/4901
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 39083fe1edab784fcd75eacbdaaf7f6affa14c9f)

Change-Id: I3d06a4b5dc76934b24ced883b1985bced35c893a
Reviewed-on: http://gerrit.openafs.org/7276
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementix.org>
---

diff --git a/src/afs/afs_util.c b/src/afs/afs_util.c
index 2b20a94ba..daf86ff4c 100644
--- a/src/afs/afs_util.c
+++ b/src/afs/afs_util.c
@@ -372,18 +372,32 @@ afs_data_pointer_to_int32(const void *p)
 afs_int32
 afs_calc_inum(afs_int32 volume, afs_int32 vnode)
 {
-    afs_int32 ino, vno = vnode;
+    afs_int32 ino = 0, vno = vnode;
     char digest[16];
     struct afs_md5 ct;
 
     if (afs_new_inum) {
+	int offset;
 	AFS_MD5_Init(&ct);
 	AFS_MD5_Update(&ct, &volume, 4);
 	AFS_MD5_Update(&ct, &vnode, 4);
 	AFS_MD5_Final(digest, &ct);
-	memcpy(&ino, digest, sizeof(afs_int32));
-	ino ^= (ino ^ vno) & 1;
-    } else {
+
+	/* Userspace may react oddly to an inode number of 0 or 1, so keep
+	 * reading more of the md5 digest if we get back one of those.
+	 * Make sure not to read beyond the end of the digest; if we somehow
+	 * still have a 0, we will fall through to the non-md5 calculation. */
+	for (offset = 0;
+	     (ino == 0 || ino == 1) &&
+	      offset + sizeof(ino) <= sizeof(digest);
+	     offset++) {
+
+	    memcpy(&ino, &digest[offset], sizeof(ino));
+	    ino ^= (ino ^ vno) & 1;
+	    ino &= 0x7fffffff;      /* Assumes 32 bit ino_t ..... */
+	}
+    }
+    if (ino == 0 || ino == 1) {
 	ino = (volume << 16) + vnode;
     }
     ino &= 0x7fffffff;      /* Assumes 32 bit ino_t ..... */