[PATCH 08/17] mount_service: read fuse.conf to enable allow_other for unprivileged mounts

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

Now that we've hoisted the fuse.conf parsing and enforcement code into a
shared file, we can make fuservicemount use the same config file for the
same kinds of parsing.  This will enable distros to install
fuservicemount as a setuid program so that unprivileged userspace can
also access containerized fuse servers.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 util/mount_service.c |   19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)


diff --git a/util/mount_service.c b/util/mount_service.c
index 2e541f67277ee5..9f6feab902f89d 100644
--- a/util/mount_service.c
+++ b/util/mount_service.c
@@ -31,6 +31,7 @@
 #include "fuse_i.h"
 #include "fuse_service_priv.h"
 #include "mount_service.h"
+#include "fuser_conf.h"
 
 struct mount_service {
 	/* prefix for printing error messages */
@@ -199,7 +200,7 @@ static int mount_service_send_hello(struct mount_service *mo)
 	};
 	ssize_t size;
 
-	if (getuid() == 0)
+	if (getuid() == 0 || user_allow_other)
 		hello.flags |= htonl(FUSE_SERVICE_FLAG_ALLOW_OTHER);
 
 	size = sendmsg(mo->sockfd, &msg, MSG_EOR | MSG_NOSIGNAL);
@@ -813,6 +814,20 @@ static int mount_service_handle_mntopts_cmd(struct mount_service *mo,
 			*equals = 0;
 		}
 
+		if (getuid() != 0 && !user_allow_other &&
+		    (!strcmp(tok, "allow_other") ||
+		     !strcmp(tok, "allow_root"))) {
+			fprintf(stderr,
+"%s: option %s only allowed if 'user_allow_other' is set in %s\n",
+				mo->msgtag, tok, FUSE_CONF);
+			return mount_service_send_reply(mo, EPERM);
+		}
+		if (!strcmp(tok, "blkdev") && getuid() != 0) {
+			fprintf(stderr, "%s: option blkdev is privileged\n",
+				mo->msgtag);
+			return mount_service_send_reply(mo, EPERM);
+		}
+
 #ifdef HAVE_NEW_MOUNT_API
 		if (mo->fsopenfd >= 0) {
 			int ret;
@@ -1347,6 +1362,8 @@ int mount_service_main(int argc, char *argv[])
 	else
 		mo.msgtag = "mount.service";
 
+	read_conf(mo.msgtag);
+
 	ret = mount_service_init(&mo, argc, argv);
 	if (ret)
 		return EXIT_FAILURE;