From: Thomas Veerman <thomas@minix3.org>
Date: Tue, 20 Nov 2012 13:14:31 +0000 (+0000)
Subject: VFS: change 'last_dir' to match locking assumption
X-Git-Tag: v3.2.1~189
X-Git-Url: http://zhaoyanbai.com/repos/%22http:/www.isc.org/icons/man.dnssec-checkds.html?a=commitdiff_plain;h=de83b2a9d9cb8f97d731db4814869534755dd016;p=minix.git

VFS: change 'last_dir' to match locking assumption

new_node makes the assumption that when it does last_dir on a path, a
successive advance would not yield a lock on a vmnt, because last_dir
already locked the vmnt. This is true except when last_dir resolves
to a directory on the parent vmnt of the file that was the result of
advance. For example,
 # cd /
 # echo foo > home
where home is on a different (sub) partition than / is (default
install). last_dir would resolve to / and advance would resolve to
/home.

With this change, last_dir resolves to the root node on the /home
partition, making the assumption valid again.
---

diff --git a/servers/vfs/open.c b/servers/vfs/open.c
index 0a0edf80f..bd945371c 100644
--- a/servers/vfs/open.c
+++ b/servers/vfs/open.c
@@ -444,9 +444,9 @@ static struct vnode *new_node(struct lookup *resolve, int oflags, mode_t bits)
 		else
 			err_code = r;
 
+		unlock_vmnt(dir_vmp);
 		unlock_vnode(dirp);
 		unlock_vnode(vp);
-		unlock_vmnt(dir_vmp);
 		put_vnode(dirp);
 		return(NULL);
 	}
diff --git a/servers/vfs/path.c b/servers/vfs/path.c
index c19f1e135..63de98f80 100644
--- a/servers/vfs/path.c
+++ b/servers/vfs/path.c
@@ -264,7 +264,9 @@ struct fproc *rfp;
 	symlink.l_vmnt_lock = VMNT_READ;
 	sym_vp = advance(res_vp, &symlink, rfp);
 
-	if (sym_vp != NULL && S_ISLNK(sym_vp->v_mode)) {
+	if (sym_vp == NULL) break;
+
+	if (S_ISLNK(sym_vp->v_mode)) {
 		/* Last component is a symlink, but if we've been asked to not
 		 * resolve it, return now.
 		 */
@@ -310,6 +312,41 @@ struct fproc *rfp;
 
 			continue;
 		}
+	} else {
+		symloop = 0;	/* Not a symlink, so restart counting */
+
+		/* If we're crossing a mount point, return root node of mount
+		 * point on which the file resides. That's the 'real' last
+		 * dir that holds the file we're looking for.
+		 */
+		if (sym_vp->v_fs_e != res_vp->v_fs_e) {
+			assert(sym_vmp != NULL);
+
+			/* Unlock final file, it might have wrong lock types */
+			unlock_vnode(sym_vp);
+			unlock_vmnt(sym_vmp);
+			put_vnode(sym_vp);
+			sym_vp = NULL;
+
+			/* Also unlock and release erroneous result */
+			unlock_vnode(*resolve->l_vnode);
+			unlock_vmnt(*resolve->l_vmp);
+			put_vnode(res_vp);
+
+			/* Relock vmnt and vnode with correct lock types */
+			lock_vmnt(sym_vmp, resolve->l_vmnt_lock);
+			lock_vnode(sym_vmp->m_root_node, resolve->l_vnode_lock);
+			res_vp = sym_vmp->m_root_node;
+			dup_vnode(res_vp);
+			*resolve->l_vnode = res_vp;
+			*resolve->l_vmp = sym_vmp;
+
+			/* We've effectively resolved the final component, so
+			 * change it to current directory to prevent future
+			 * 'advances' of returning erroneous results.
+			 */
+			strlcpy(dir_entry, ".", NAME_MAX+1);
+		}
 	}
 	break;
   } while (symloop < SYMLOOP_MAX);