libmount: add fsconfig() btrfs workaround

The new kernel mount API is not properly implemented in all FS
drivers. See strace output:

fsconfig(3, FSCONFIG_SET_STRING, "source", "/dev/sda", 0) = 0
fsconfig(3, FSCONFIG_SET_STRING, "context", "system_u:object_r:root_t:s0", 0) = 0
fsconfig(3, FSCONFIG_CMD_CREATE, NULL, NULL, 0) = -1 EINVAL (Invalid argument)

Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Signed-off-by: Karel Zak <kzak@redhat.com>

4 files changed, 26 insertions, 2 deletions

diff --git a/libmount/src/context.c b/libmount/src/context.c
index 972853b3f..8db6b6950 100644
--- a/libmount/src/context.c
+++ b/libmount/src/context.c
@@ -165,6 +165,7 @@ int mnt_reset_context(struct libmnt_context *cxt)
 	cxt->mountdata = NULL;
 	cxt->flags = MNT_FL_DEFAULT;
 	cxt->noautofs = 1;
+	cxt->has_selinux_opt = 0;
 
 	cxt->map_linux = mnt_get_builtin_optmap(MNT_LINUX_MAP);
 	cxt->map_userspace = mnt_get_builtin_optmap(MNT_USERSPACE_MAP);
@@ -288,6 +289,7 @@ struct libmnt_context *mnt_copy_context(struct libmnt_context *o)
 	n->table_fltrcb_data = o->table_fltrcb_data;
 
 	n->noautofs = o->noautofs;
+	n->has_selinux_opt = o->has_selinux_opt;
 
 	return n;
 failed:
diff --git a/libmount/src/context_mount.c b/libmount/src/context_mount.c
index d81741ea5..7491ec205 100644
--- a/libmount/src/context_mount.c
+++ b/libmount/src/context_mount.c
@@ -169,6 +169,9 @@ static int fix_optstr(struct libmnt_context *cxt)
 					rc = mnt_opt_set_quoted_value(opt, raw);
 				if (raw)
 					freecon(raw);
+
+				/* temporary for broken fsconfig() syscall */
+				cxt->has_selinux_opt = 1;
 			}
 			if (rc)
 				goto done;
diff --git a/libmount/src/hook_mount.c b/libmount/src/hook_mount.c
index 09a1f3f32..c60c3513b 100644
--- a/libmount/src/hook_mount.c
+++ b/libmount/src/hook_mount.c
@@ -120,7 +120,7 @@ static int configure_superblock(struct libmnt_context *cxt,
 	struct libmnt_opt *opt;
 	int rc;
 
-	DBG(HOOK, ul_debugobj(hs, " configure FS"));
+	DBG(HOOK, ul_debugobj(hs, " config FS"));
 
 	ol = mnt_context_get_optlist(cxt);
 	if (!ol)
@@ -150,6 +150,7 @@ static int configure_superblock(struct libmnt_context *cxt,
 			return -errno;
 	}
 
+	DBG(HOOK, ul_debugobj(hs, " config done [rc=0]"));
 	return 0;
 }
 
@@ -231,7 +232,7 @@ static int hook_create_mount(struct libmnt_context *cxt,
 	if (!src)
 		return -EINVAL;
 
-	DBG(HOOK, ul_debugobj(hs, "create FS instance"));
+	DBG(HOOK, ul_debugobj(hs, "init FS"));
 
 	rc = fsconfig(api->fd_fs, FSCONFIG_SET_STRING, "source", src, 0);
 	set_syscall_status(cxt, "fsconfig", rc == 0);
@@ -239,6 +240,7 @@ static int hook_create_mount(struct libmnt_context *cxt,
 	if (!rc)
 		rc = configure_superblock(cxt, hs, api->fd_fs);
 	if (!rc) {
+		DBG(HOOK, ul_debugobj(hs, "create FS"));
 		rc = fsconfig(api->fd_fs, FSCONFIG_CMD_CREATE, NULL, NULL, 0);
 		set_syscall_status(cxt, "fsconfig", rc == 0);
 	}
@@ -551,6 +553,22 @@ static int hook_prepare(struct libmnt_context *cxt,
 	assert(cxt);
 	assert(hs == &hookset_mount);
 
+	/*
+	 * The current kernel btrfs driver does not completely implement
+	 * fsconfig() as it does not work with selinux stuff.
+	 *
+	 * Don't use the new mount API in this situation. Let's hope this issue
+	 * is temporary.
+	 */
+	{
+		const char *type = mnt_fs_get_fstype(cxt->fs);
+
+		if (type && strcmp(type, "btrfs") == 0 && cxt->has_selinux_opt) {
+			DBG(HOOK, ul_debugobj(hs, "don't use new API (btrfs issue)"));
+			return 0;
+		}
+	}
+
 	DBG(HOOK, ul_debugobj(hs, "prepare mount"));
 
 	ol = mnt_context_get_optlist(cxt);
diff --git a/libmount/src/mountP.h b/libmount/src/mountP.h
index 0d341c65a..80015f94c 100644
--- a/libmount/src/mountP.h
+++ b/libmount/src/mountP.h
@@ -427,6 +427,7 @@ struct libmnt_context
 
 	unsigned int	enabled_textdomain : 1;	/* bindtextdomain() called */
 	unsigned int	noautofs : 1;		/* ignore autofs mounts */
+	unsigned int	has_selinux_opt : 1;	/* temporary for broken fsconfig() syscall */
 
 	struct list_head	hooksets_datas;	/* global hooksets data */
 	struct list_head	hooksets_hooks;	/* global hooksets data */