[PATCH] afs: Fix updating of i_mode due to 3rd party change

[David Howells]

Fix afs_apply_status() to mask off the irrelevant bits from status->mode
when OR'ing them into i_mode.  This can happen when a 3rd party chmod
occurs.

Also fix afs_inode_init_from_status() to mask off the mode bits when
initialising i_mode.

Fixes: 260a980317da ("[AFS]: Add "directory write" support.")
Reported-by: Al Viro <v...@zeniv.linux.org.uk>
Signed-off-by: David Howells <dhowe...@redhat.com>
---

 fs/afs/inode.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/afs/inode.c b/fs/afs/inode.c
index b0d7b892090d..d68abb9804b6 100644
--- a/fs/afs/inode.c
+++ b/fs/afs/inode.c
@@ -74,6 +74,7 @@ static int afs_inode_init_from_status(struct afs_operation 
*op,
        struct afs_file_status *status = &vp->scb.status;
        struct inode *inode = AFS_VNODE_TO_I(vnode);
        struct timespec64 t;
+       mode_t mode = status->mode & S_IALLUGO;
 
        _enter("{%llx:%llu.%u} %s",
               vp->fid.vid, vp->fid.vnode, vp->fid.unique,
@@ -103,13 +104,13 @@ static int afs_inode_init_from_status(struct 
afs_operation *op,
 
        switch (status->type) {
        case AFS_FTYPE_FILE:
-               inode->i_mode   = S_IFREG | status->mode;
+               inode->i_mode   = S_IFREG | mode;
                inode->i_op     = &afs_file_inode_operations;
                inode->i_fop    = &afs_file_operations;
                inode->i_mapping->a_ops = &afs_fs_aops;
                break;
        case AFS_FTYPE_DIR:
-               inode->i_mode   = S_IFDIR | status->mode;
+               inode->i_mode   = S_IFDIR | mode;
                inode->i_op     = &afs_dir_inode_operations;
                inode->i_fop    = &afs_dir_file_operations;
                inode->i_mapping->a_ops = &afs_dir_aops;
@@ -126,7 +127,7 @@ static int afs_inode_init_from_status(struct afs_operation 
*op,
                        inode->i_fop    = &afs_mntpt_file_operations;
                        inode->i_mapping->a_ops = &afs_fs_aops;
                } else {
-                       inode->i_mode   = S_IFLNK | status->mode;
+                       inode->i_mode   = S_IFLNK | mode;
                        inode->i_op     = &afs_symlink_inode_operations;
                        inode->i_mapping->a_ops = &afs_fs_aops;
                }
@@ -199,7 +200,7 @@ static void afs_apply_status(struct afs_operation *op,
        if (status->mode != vnode->status.mode) {
                mode = inode->i_mode;
                mode &= ~S_IALLUGO;
-               mode |= status->mode;
+               mode |= status->mode & S_IALLUGO;
                WRITE_ONCE(inode->i_mode, mode);
        }