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>

3 files changed, 14 insertions, 7 deletions

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 9656907f4b81..fa3c1541151c 100644
--- a/fs/udf/inode.c
+++ b/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) <<
diff --git a/fs/udf/super.c b/fs/udf/super.c
index e54960c0e960..f06cc67cf864 100644
--- a/fs/udf/super.c
+++ b/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);
diff --git a/fs/udf/udf_sb.h b/fs/udf/udf_sb.h
index 9f38a6ca4fd5..4858c191242b 100644
--- a/fs/udf/udf_sb.h
+++ b/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;