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/inode.c

@@ -648,7 +648,7 @@ static int sdcardfs_permission(struct vfsmount *mnt, struct inode *inode, int ma
 	 */
 	copy_attrs(&tmp, inode);
 	tmp.i_uid = make_kuid(&init_user_ns, top->d_uid);
-	tmp.i_gid = make_kgid(&init_user_ns, get_gid(mnt, top));
+	tmp.i_gid = make_kgid(&init_user_ns, get_gid(mnt, inode->i_sb, top));
 	tmp.i_mode = (inode->i_mode & S_IFMT)
 			| get_mode(mnt, SDCARDFS_I(inode), top);
 	data_put(top);
@@ -727,7 +727,7 @@ static int sdcardfs_setattr(struct vfsmount *mnt, struct dentry *dentry, struct
 	 */
 	copy_attrs(&tmp, inode);
 	tmp.i_uid = make_kuid(&init_user_ns, top->d_uid);
-	tmp.i_gid = make_kgid(&init_user_ns, get_gid(mnt, top));
+	tmp.i_gid = make_kgid(&init_user_ns, get_gid(mnt, dentry->d_sb, top));
 	tmp.i_mode = (inode->i_mode & S_IFMT)
 			| get_mode(mnt, SDCARDFS_I(inode), top);
 	tmp.i_size = i_size_read(inode);
@@ -829,6 +829,7 @@ static int sdcardfs_fillattr(struct vfsmount *mnt,
 {
 	struct sdcardfs_inode_info *info = SDCARDFS_I(inode);
 	struct sdcardfs_inode_data *top = top_data_get(info);
+	struct super_block *sb = inode->i_sb;
 
 	if (!top)
 		return -EINVAL;
@@ -838,7 +839,7 @@ static int sdcardfs_fillattr(struct vfsmount *mnt,
 	stat->mode = (inode->i_mode  & S_IFMT) | get_mode(mnt, info, top);
 	stat->nlink = inode->i_nlink;
 	stat->uid = make_kuid(&init_user_ns, top->d_uid);
-	stat->gid = make_kgid(&init_user_ns, get_gid(mnt, top));
+	stat->gid = make_kgid(&init_user_ns, get_gid(mnt, sb, top));
 	stat->rdev = inode->i_rdev;
 	stat->size = i_size_read(inode);
 	stat->atime = inode->i_atime;

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;
+	opts->default_normal = false;
 
 	*debug = 0;
 
@@ -122,6 +125,9 @@ 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:
+			opts->default_normal = true;
+			break;
 		/* unknown option */
 		default:
 			if (!silent)
@@ -175,6 +181,7 @@ 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

@@ -220,6 +220,7 @@ struct sdcardfs_mount_options {
 	userid_t fs_user_id;
 	bool multiuser;
 	bool gid_derivation;
+	bool default_normal;
 	unsigned int reserved_mb;
 };
 
@@ -413,11 +414,13 @@ static inline void set_top(struct sdcardfs_inode_info *info,
 }
 
 static inline int get_gid(struct vfsmount *mnt,
+		struct super_block *sb,
 		struct sdcardfs_inode_data *data)
 {
-	struct sdcardfs_vfsmount_options *opts = mnt->data;
+	struct sdcardfs_vfsmount_options *vfsopts = mnt->data;
+	struct sdcardfs_sb_info *sbi = SDCARDFS_SB(sb);
 
-	if (opts->gid == AID_SDCARD_RW)
+	if (vfsopts->gid == AID_SDCARD_RW && !sbi->options.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
@@ -426,7 +429,7 @@ static inline int get_gid(struct vfsmount *mnt,
 		 */
 		return AID_SDCARD_RW;
 	else
-		return multiuser_get_uid(data->userid, opts->gid);
+		return multiuser_get_uid(data->userid, vfsopts->gid);
 }
 
 static inline int get_mode(struct vfsmount *mnt,

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 (opts->default_normal)
+		seq_puts(m, ",default_normal");
 	if (opts->reserved_mb != 0)
 		seq_printf(m, ",reserved=%uMB", opts->reserved_mb);