cluster: RHEL6 - fsck.gfs2: Fix buffer overflow in get_lockproto_table

[Andrew Price]

Gitweb:       
http://git.fedorahosted.org/git/?p=cluster.git;a=commitdiff;h=f796ee87527...
Commit:        f796ee8752712e9e523e1516bb9165b274552753
Parent:        638deec0ccbf45862eee97294f09ba9d6b3f56d0
Author:        Andrew Price <anprice(a)redhat.com&gt;
AuthorDate:    Sat Jul 7 22:03:24 2012 +0100
Committer:     Andrew Price <anprice(a)redhat.com&gt;
CommitterDate: Thu Aug 16 21:54:56 2012 +0100

fsck.gfs2: Fix buffer overflow in get_lockproto_table

Coverity discovered a buffer overflow in this function where an overly
long cluster name in cluster.conf could cause a crash while repairing
the superblock. This patch fixes the bug by making sure the lock table
is composed sensibly, limiting the fsname to 16 chars as documented, and
only allowing the cluster name (which doesn't seem to have a documented
max size) to use the remaining space in the locktable name string.

Resolves: rhbz#838945

Signed-off-by: Andrew Price <anprice(a)redhat.com&gt;
---
 gfs2/fsck/initialize.c |   42 ++++++++++++++++++++++--------------------
 1 files changed, 22 insertions(+), 20 deletions(-)

diff --git a/gfs2/fsck/initialize.c b/gfs2/fsck/initialize.c
index 28fe03d..558fd03 100644
--- a/gfs2/fsck/initialize.c
+++ b/gfs2/fsck/initialize.c
@@ -750,12 +750,13 @@ static int init_system_inodes(struct gfs2_sbd *sdp)
 static int get_lockproto_table(struct gfs2_sbd *sdp)
 {
 	FILE *fp;
-	char line[PATH_MAX], *p, *p2;
-	char fsname[PATH_MAX];
+	char line[PATH_MAX];
+	char *cluname, *end;
+	const char *fsname, *cfgfile = "/etc/cluster/cluster.conf";
 
 	memset(sdp->lockproto, 0, sizeof(sdp->lockproto));
 	memset(sdp->locktable, 0, sizeof(sdp->locktable));
-	fp = fopen("/etc/cluster/cluster.conf", "rt");
+	fp = fopen(cfgfile, "rt");
 	if (!fp) {
 		/* no cluster.conf; must be a stand-alone file system */
 		strcpy(sdp->lockproto, "lock_nolock");
@@ -768,28 +769,29 @@ static int get_lockproto_table(struct gfs2_sbd *sdp)
 	log_warn(_("Lock protocol assumed to be: " GFS2_DEFAULT_LOCKPROTO
 		   "\n"));
 	strcpy(sdp->lockproto, GFS2_DEFAULT_LOCKPROTO);
+
 	while (fgets(line, sizeof(line) - 1, fp)) {
-		p = strstr(line,"<cluster name=");
-		if (p) {
-			p += 15;
-			p2 = strchr(p,'"');
-			strncpy(sdp->locktable, p, p2 - p);
+		cluname = strstr(line,"<cluster name=");
+		if (cluname) {
+			cluname += 15;
+			end = strchr(cluname,'"');
+			if (end)
+				*end = '\0';
 			break;
 		}
 	}
-	if (sdp->locktable[0] == '\0') {
-		log_err(_("Error: Unable to determine cluster name from "
-			  "/etc/cluster.conf\n"));
+	if (cluname == NULL || end == NULL || end - cluname < 1) {
+		log_err(_("Error: Unable to determine cluster name from %s\n"),
+		                                                      cfgfile);
 	} else {
-		memset(fsname, 0, sizeof(fsname));
-		p = strrchr(opts.device, '/');
-		if (p) {
-			p++;
-			strncpy(fsname, p, sizeof(fsname));
-		} else
-			strcpy(fsname, "repaired");
-		strcat(sdp->locktable, ":");
-		strcat(sdp->locktable, fsname);
+		fsname = strrchr(opts.device, '/');
+		if (fsname)
+			fsname++;
+		else
+			fsname = "repaired";
+		snprintf(sdp->locktable, sizeof(sdp->locktable), "%.*s:%.16s",
+		         (int)(sizeof(sdp->locktable) - strlen(fsname) - 2),
+		         cluname, fsname);
 		log_warn(_("Lock table determined to be: %s\n"),
 			 sdp->locktable);
 	}