[Cluster-devel] [PATCH 2/2] fsck.gfs2: Fix buffer overflow in get_lockproto_table

[Andrew Price <anprice@redhat.com>]

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.

Signed-off-by: Andrew Price <anprice@redhat.com>
---
 gfs2/fsck/initialize.c |   42 ++++++++++++++++++++++--------------------
 1 file changed, 22 insertions(+), 20 deletions(-)

diff --git a/gfs2/fsck/initialize.c b/gfs2/fsck/initialize.c
index f07e0b2..e56161e 100644
--- a/gfs2/fsck/initialize.c
+++ b/gfs2/fsck/initialize.c
@@ -753,12 +753,13 @@ 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");
@@ -771,28 +772,29 @@ 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);
 	}
-- 
1.7.10.4