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authorVivek Goyal <vgoyal@redhat.com>2016-07-01 16:34:29 -0400
committerMiklos Szeredi <mszeredi@redhat.com>2016-07-29 12:05:23 +0200
commit754f8cb72b42a3a6100d2bbb1cb885361a7310dd (patch)
tree307370378a607f2882df396417aaebed1ef1f590
parent1175b6b8d96331676f1d436b089b965807f23b4a (diff)
downloadlinux-754f8cb72b42a3a6100d2bbb1cb885361a7310dd.tar.bz2
ovl: do not require mounter to have MAY_WRITE on lower
Now we have two levels of checks in ovl_permission(). overlay inode is checked with the creds of task while underlying inode is checked with the creds of mounter. Looks like mounter does not have to have WRITE access to files on lower/. So remove the MAY_WRITE from access mask for checks on underlying lower inode. This means task should still have the MAY_WRITE permission on lower inode and mounter is not required to have MAY_WRITE. It also solves the problem of read only NFS mounts being used as lower. If __inode_permission(lower_inode, MAY_WRITE) is called on read only NFS, it fails. By resetting MAY_WRITE, check succeeds and case of read only NFS shold work with overlay without having to specify any special mount options (default permission). Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
-rw-r--r--fs/overlayfs/inode.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 5becbaf1cec7..8f7dd547cfb3 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -184,6 +184,8 @@ int ovl_permission(struct inode *inode, int mask)
return err;
old_cred = ovl_override_creds(inode->i_sb);
+ if (!is_upper)
+ mask &= ~(MAY_WRITE | MAY_APPEND);
err = __inode_permission(realinode, mask);
revert_creds(old_cred);