[Cluster-devel] [PATCH RHEL6] libgfs2: Use a matching context mount option in mount_gfs2_meta

[Andrew Price <anprice@redhat.com>]

On a system with SELinux enabled, if a gfs2 file system is mounted with
a context= option, the tools gfs2_quota, gfs2_tool, gfs2_grow and
gfs2_jadd will fail with "Device or resource busy". This is due to
SELinux failing the mount due to a mismatched context ("SELinux: mount
invalid.  Same superblock, different security settings").

In order to work around this, parse the context option of the gfs2 mount
point in is_pathname_mounted() and use it in mount_gfs2_meta().

Resolves: rhbz#1121693

Signed-off-by: Andrew Price <anprice@redhat.com>
---
 gfs2/libgfs2/libgfs2.h |  1 +
 gfs2/libgfs2/misc.c    | 21 ++++++++++++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/gfs2/libgfs2/libgfs2.h b/gfs2/libgfs2/libgfs2.h
index 9c20f11..25286d1 100644
--- a/gfs2/libgfs2/libgfs2.h
+++ b/gfs2/libgfs2/libgfs2.h
@@ -217,6 +217,7 @@ struct gfs2_sbd {
 
 	int device_fd;
 	int path_fd;
+	char *secontext;
 
 	uint64_t sb_addr;
 
diff --git a/gfs2/libgfs2/misc.c b/gfs2/libgfs2/misc.c
index 8e0ca6f..5ef4a2a 100644
--- a/gfs2/libgfs2/misc.c
+++ b/gfs2/libgfs2/misc.c
@@ -100,6 +100,24 @@ int compute_constants(struct gfs2_sbd *sdp)
 	return 0;
 }
 
+/**
+ * Returns a duplicate of the 'context' mount option, or NULL if not found.
+ */
+static char *copy_context_opt(struct mntent *mnt)
+{
+	char *ctx, *end;
+
+	ctx = hasmntopt(mnt, "context");
+	if (ctx == NULL)
+		return NULL;
+
+	end = strchr(ctx, ',');
+	if (end == NULL)
+		return NULL;
+
+	return strndup(ctx, end - ctx);
+}
+
 int is_pathname_mounted(struct gfs2_sbd *sdp, int *ro_mount)
 {
 	FILE *fp;
@@ -161,6 +179,7 @@ int is_pathname_mounted(struct gfs2_sbd *sdp, int *ro_mount)
 		return 0;
 	if (hasmntopt(mnt, MNTOPT_RO))
                *ro_mount = 1;
+	sdp->secontext = copy_context_opt(mnt);
 	return 1; /* mounted */
 }
 
@@ -319,7 +338,7 @@ int mount_gfs2_meta(struct gfs2_sbd *sdp)
 	sigaction(SIGCONT, &sa, NULL);
 	sigaction(SIGUSR1, &sa, NULL);
 	sigaction(SIGUSR2, &sa, NULL);
-	ret = mount(sdp->path_name, sdp->metafs_path, "gfs2meta", 0, NULL);
+	ret = mount(sdp->path_name, sdp->metafs_path, "gfs2meta", 0, sdp->secontext);
 	if (ret) {
 		rmdir(sdp->metafs_path);
 		return -1;
-- 
1.9.3