disable most mode changes on non-unix/non-cifsacl mounts

CIFS currently allows you to change the mode of an inode on a share that
doesn't have unix extensions enabled, and isn't using cifsacl. The inode
in this case *only* has its mode changed in memory on the client. This
is problematic since it can change any time the inode is purged from the
cache.

This patch makes cifs_setattr silently ignore most mode changes when
unix extensions and cifsacl support are not enabled, and when the share
is not mounted with the "dynperm" option. The exceptions are:

When a mode change would remove all write access to an inode we turn on
the ATTR_READONLY bit on the server and remove all write bits from the
inode's mode in memory.

When a mode change would add a write bit to an inode that previously had
them all turned off, it turns off the ATTR_READONLY bit on the server,
and resets the mode back to what it would normally be (generally, the
file_mode or dir_mode of the share).

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 26 insertions, 12 deletions

diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
index fe752fdb26c3..722be543ceec 100644
--- a/fs/cifs/inode.c
+++ b/fs/cifs/inode.c
@@ -1575,7 +1575,7 @@ int cifs_setattr(struct dentry *direntry, struct iattr *attrs)
                 attrs->ia_valid &= ~ATTR_MODE;
 
         if (attrs->ia_valid & ATTR_MODE) {
-                cFYI(1, ("Mode changed to 0x%x", attrs->ia_mode));
+                cFYI(1, ("Mode changed to 0%o", attrs->ia_mode));
                 mode = attrs->ia_mode;
         }
 
@@ -1590,18 +1590,18 @@ int cifs_setattr(struct dentry *direntry, struct iattr *attrs)
 #ifdef CONFIG_CIFS_EXPERIMENTAL
                 if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_ACL)
                         rc = mode_to_acl(inode, full_path, mode);
-                else if ((mode & S_IWUGO) == 0) {
-#else
-                if ((mode & S_IWUGO) == 0) {
+                else
 #endif
-                        /* not writeable */
-                        if ((cifsInode->cifsAttrs & ATTR_READONLY) == 0) {
-                                set_dosattr = true;
-                                time_buf.Attributes =
-                                        cpu_to_le32(cifsInode->cifsAttrs |
-                                                    ATTR_READONLY);
-                        }
-                } else if (cifsInode->cifsAttrs & ATTR_READONLY) {
+                if (((mode & S_IWUGO) == 0) &&
+                    (cifsInode->cifsAttrs & ATTR_READONLY) == 0) {
+                        set_dosattr = true;
+                        time_buf.Attributes = cpu_to_le32(cifsInode->cifsAttrs |
+                                                          ATTR_READONLY);
+                        /* fix up mode if we're not using dynperm */
+                        if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_DYNPERM) == 0)
+                                attrs->ia_mode = inode->i_mode & ~S_IWUGO;
+                } else if ((mode & S_IWUGO) &&
+                           (cifsInode->cifsAttrs & ATTR_READONLY)) {
                         /* If file is readonly on server, we would
                         not be able to write to it - so if any write
                         bit is enabled for user or group or other we
@@ -1612,6 +1612,20 @@ int cifs_setattr(struct dentry *direntry, struct iattr *attrs)
                         /* Windows ignores set to zero */
                         if (time_buf.Attributes == 0)
                                 time_buf.Attributes |= cpu_to_le32(ATTR_NORMAL);
+
+                        /* reset local inode permissions to normal */
+                        if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_DYNPERM)) {
+                                attrs->ia_mode &= ~(S_IALLUGO);
+                                if (S_ISDIR(inode->i_mode))
+                                        attrs->ia_mode |=
+                                                cifs_sb->mnt_dir_mode;
+                                else
+                                        attrs->ia_mode |=
+                                                cifs_sb->mnt_file_mode;
+                        }
+                } else if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_DYNPERM)) {
+                        /* ignore mode change - ATTR_READONLY hasn't changed */
+                        attrs->ia_valid &= ~ATTR_MODE;
                 }
         }