udf: Protect default inode credentials by rwlock

Superblock carries credentials (uid, gid, etc.) which are used as default
values in __udf_read_inode() when media does not provide these. These
credentials can change during remount so we protect them by a rwlock so that
each inode gets a consistent set of credentials.
Signed-off-by: Jan Kara <jack@suse.cz>

fs/udf/inode.c

@@ -1201,6 +1201,7 @@ static void udf_fill_inode(struct inode *inode, struct buffer_head *bh)
 		return;
 	}
 
+	read_lock(&sbi->s_cred_lock);
 	inode->i_uid = le32_to_cpu(fe->uid);
 	if (inode->i_uid == -1 ||
 	    UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_UID_IGNORE) ||
@@ -1213,13 +1214,6 @@ static void udf_fill_inode(struct inode *inode, struct buffer_head *bh)
 	    UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_GID_SET))
 		inode->i_gid = UDF_SB(inode->i_sb)->s_gid;
 
-	inode->i_nlink = le16_to_cpu(fe->fileLinkCount);
-	if (!inode->i_nlink)
-		inode->i_nlink = 1;
-
-	inode->i_size = le64_to_cpu(fe->informationLength);
-	iinfo->i_lenExtents = inode->i_size;
-
 	if (fe->icbTag.fileType != ICBTAG_FILE_TYPE_DIRECTORY &&
 			sbi->s_fmode != UDF_INVALID_MODE)
 		inode->i_mode = sbi->s_fmode;
@@ -1229,6 +1223,14 @@ static void udf_fill_inode(struct inode *inode, struct buffer_head *bh)
 	else
 		inode->i_mode = udf_convert_permissions(fe);
 	inode->i_mode &= ~sbi->s_umask;
+	read_unlock(&sbi->s_cred_lock);
+
+	inode->i_nlink = le16_to_cpu(fe->fileLinkCount);
+	if (!inode->i_nlink)
+		inode->i_nlink = 1;
+
+	inode->i_size = le64_to_cpu(fe->informationLength);
+	iinfo->i_lenExtents = inode->i_size;
 
 	if (iinfo->i_efe == 0) {
 		inode->i_blocks = le64_to_cpu(fe->logicalBlocksRecorded) <<

fs/udf/super.c

@@ -568,12 +568,14 @@ static int udf_remount_fs(struct super_block *sb, int *flags, char *options)
 		return -EINVAL;
 
 	lock_kernel();
+	write_lock(&sbi->s_cred_lock);
 	sbi->s_flags = uopt.flags;
 	sbi->s_uid   = uopt.uid;
 	sbi->s_gid   = uopt.gid;
 	sbi->s_umask = uopt.umask;
 	sbi->s_fmode = uopt.fmode;
 	sbi->s_dmode = uopt.dmode;
+	write_unlock(&sbi->s_cred_lock);
 
 	if (sbi->s_lvid_bh) {
 		int write_rev = le16_to_cpu(udf_sb_lvidiu(sbi)->minUDFWriteRev);
@@ -1960,6 +1962,7 @@ static int udf_fill_super(struct super_block *sb, void *options, int silent)
 	sbi->s_fmode = uopt.fmode;
 	sbi->s_dmode = uopt.dmode;
 	sbi->s_nls_map = uopt.nls_map;
+	rwlock_init(&sbi->s_cred_lock);
 
 	if (uopt.session == 0xFFFFFFFF)
 		sbi->s_session = udf_get_last_session(sb);

fs/udf/udf_sb.h

@@ -129,6 +129,8 @@ struct udf_sb_info {
 	uid_t			s_uid;
 	mode_t			s_fmode;
 	mode_t			s_dmode;
+	/* Lock protecting consistency of above permission settings */
+	rwlock_t		s_cred_lock;
 
 	/* Root Info */
 	struct timespec		s_record_time;