udf: Clean up handling of invalid uid/gid

Current code relies on the fact that invalid uid/gid as defined by UDF
2.60 3.3.3.1 and 3.3.3.2 coincides with invalid uid/gid as used by the
user namespaces implementation. Since this is only lucky coincidence,
clean this up to avoid future surprises in case user namespaces
implementation changes. Also this is more robust in presence of valid
(from UDF point of view) uids / gids which do not map into current user
namespace.

Reviewed-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

2 files changed, 15 insertions, 8 deletions

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 9021c15cec17..c80765d62f7e 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -1275,6 +1275,7 @@ static int udf_read_inode(struct inode *inode, bool hidden_inode)
         unsigned int indirections = 0;
         int bs = inode->i_sb->s_blocksize;
         int ret = -EIO;
+        uint32_t uid, gid;
 
 reread:
         if (iloc->partitionReferenceNum >= sbi->s_partitions) {
@@ -1400,15 +1401,19 @@ reread:
 
         ret = -EIO;
         read_lock(&sbi->s_cred_lock);
-        i_uid_write(inode, le32_to_cpu(fe->uid));
-        if (!uid_valid(inode->i_uid) ||
+        uid = le32_to_cpu(fe->uid);
+        if (uid == UDF_INVALID_ID ||
             UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_UID_SET))
-                inode->i_uid = UDF_SB(inode->i_sb)->s_uid;
+                inode->i_uid = sbi->s_uid;
+        else
+                i_uid_write(inode, uid);
 
-        i_gid_write(inode, le32_to_cpu(fe->gid));
-        if (!gid_valid(inode->i_gid) ||
+        gid = le32_to_cpu(fe->gid);
+        if (gid == UDF_INVALID_ID ||
             UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_GID_SET))
-                inode->i_gid = UDF_SB(inode->i_sb)->s_gid;
+                inode->i_gid = sbi->s_gid;
+        else
+                i_gid_write(inode, gid);
 
         if (fe->icbTag.fileType != ICBTAG_FILE_TYPE_DIRECTORY &&
                         sbi->s_fmode != UDF_INVALID_MODE)
@@ -1653,12 +1658,12 @@ static int udf_update_inode(struct inode *inode, int do_sync)
         }
 
         if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_UID_FORGET))
-                fe->uid = cpu_to_le32(-1);
+                fe->uid = cpu_to_le32(UDF_INVALID_ID);
         else
                 fe->uid = cpu_to_le32(i_uid_read(inode));
 
         if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_GID_FORGET))
-                fe->gid = cpu_to_le32(-1);
+                fe->gid = cpu_to_le32(UDF_INVALID_ID);
         else
                 fe->gid = cpu_to_le32(i_gid_read(inode));
 
diff --git a/fs/udf/udfdecl.h b/fs/udf/udfdecl.h
index f5e0fe78979e..68e8a64d22e0 100644
--- a/fs/udf/udfdecl.h
+++ b/fs/udf/udfdecl.h
@@ -48,6 +48,8 @@ extern __printf(3, 4) void _udf_warn(struct super_block *sb,
 #define UDF_EXTENT_LENGTH_MASK  0x3FFFFFFF
 #define UDF_EXTENT_FLAG_MASK    0xC0000000
 
+#define UDF_INVALID_ID ((uint32_t)-1)
+
 #define UDF_NAME_PAD            4
 #define UDF_NAME_LEN            254
 #define UDF_NAME_LEN_CS0        255