ANDROID: sdcardfs: Add default_normal option

The default_normal option causes mounts with the gid set to
AID_SDCARD_RW to have user specific gids, as in the normal case.

Signed-off-by: Daniel Rosenberg <drosen@google.com>
Change-Id: I9619b8ac55f41415df943484dc8db1ea986cef6f
Bug: 64672411

fs/sdcardfs/main.c

@@ -33,6 +33,7 @@ enum {
 	Opt_userid,
 	Opt_reserved_mb,
 	Opt_gid_derivation,
+	Opt_default_normal,
 	Opt_err,
 };
 
@@ -45,6 +46,7 @@ static const match_table_t sdcardfs_tokens = {
 	{Opt_userid, "userid=%d"},
 	{Opt_multiuser, "multiuser"},
 	{Opt_gid_derivation, "derive_gid"},
+	{Opt_default_normal, "default_normal"},
 	{Opt_reserved_mb, "reserved_mb=%u"},
 	{Opt_err, NULL}
 };
@@ -68,6 +70,7 @@ static int parse_options(struct super_block *sb, char *options, int silent,
 	opts->reserved_mb = 0;
 	/* by default, gid derivation is off */
 	opts->gid_derivation = false;
+	vfsopts->default_normal = false;
 
 	*debug = 0;
 
@@ -122,6 +125,8 @@ static int parse_options(struct super_block *sb, char *options, int silent,
 		case Opt_gid_derivation:
 			opts->gid_derivation = true;
 			break;
+		case Opt_default_normal:
+			vfsopts->default_normal = true;
 		/* unknown option */
 		default:
 			if (!silent)
@@ -175,6 +180,7 @@ int parse_options_remount(struct super_block *sb, char *options, int silent,
 				return 0;
 			vfsopts->mask = option;
 			break;
+		case Opt_default_normal:
 		case Opt_multiuser:
 		case Opt_userid:
 		case Opt_fsuid:

fs/sdcardfs/sdcardfs.h

@@ -224,6 +224,7 @@ struct sdcardfs_mount_options {
 struct sdcardfs_vfsmount_options {
 	gid_t gid;
 	mode_t mask;
+	bool default_normal;
 };
 
 extern int parse_options_remount(struct super_block *sb, char *options, int silent,
@@ -415,7 +416,7 @@ static inline int get_gid(struct vfsmount *mnt,
 {
 	struct sdcardfs_vfsmount_options *opts = mnt->data;
 
-	if (opts->gid == AID_SDCARD_RW)
+	if (opts->gid == AID_SDCARD_RW && !opts->default_normal)
 		/* As an optimization, certain trusted system components only run
 		 * as owner but operate across all users. Since we're now handing
 		 * out the sdcard_rw GID only to trusted apps, we're okay relaxing

fs/sdcardfs/super.c

@@ -304,6 +304,8 @@ static int sdcardfs_show_options(struct vfsmount *mnt, struct seq_file *m,
 		seq_printf(m, ",userid=%u", opts->fs_user_id);
 	if (opts->gid_derivation)
 		seq_puts(m, ",derive_gid");
+	if (vfsopts->default_normal)
+		seq_puts(m, ",default_normal");
 	if (opts->reserved_mb != 0)
 		seq_printf(m, ",reserved=%uMB", opts->reserved_mb);