ovl: setattr: check permissions before copy-up

Without this copy-up of a file can be forced, even without actually being
allowed to do anything on the file.

[Arnd Bergmann] include <linux/pagemap.h> for PAGE_CACHE_SIZE (used by
MAX_LFS_FILESIZE definition).

Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Cc: <stable@vger.kernel.org>

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 7654631..213a726 100644 (file)
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -45,6 +45,19 @@ int ovl_setattr(struct dentry *dentry, struct iattr *attr)
        int err;
        struct dentry *upperdentry;
 
+       /*
+        * Check for permissions before trying to copy-up.  This is redundant
+        * since it will be rechecked later by ->setattr() on upper dentry.  But
+        * without this, copy-up can be triggered by just about anybody.
+        *
+        * We don't initialize inode->size, which just means that
+        * inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
+        * check for a swapfile (which this won't be anyway).
+        */
+       err = inode_change_ok(dentry->d_inode, attr);
+       if (err)
+               return err;
+
        err = ovl_want_write(dentry);
        if (err)
                goto out;

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index ec31711..b08bf4d 100644 (file)
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -9,6 +9,7 @@
 
 #include <linux/fs.h>
 #include <linux/namei.h>
+#include <linux/pagemap.h>
 #include <linux/xattr.h>
 #include <linux/security.h>
 #include <linux/mount.h>
@@ -936,6 +937,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
        }
 
        sb->s_stack_depth = 0;
+       sb->s_maxbytes = MAX_LFS_FILESIZE;
        if (ufs->config.upperdir) {
                if (!ufs->config.workdir) {
                        pr_err("overlayfs: missing 'workdir'\n");