4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Miklos Szeredi <miklos@xxxxxxxxxx>
commit cf9a6784f7c1b5ee2b9159a1246e327c331c5697 upstream.
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@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/overlayfs/inode.c | 13 +++++++++++++
fs/overlayfs/super.c | 2 ++
2 files changed, 15 insertions(+)
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -42,6 +42,19 @@ int ovl_setattr(struct dentry *dentry, s
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;
--- 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>
@@ -910,6 +911,7 @@ static int ovl_fill_super(struct super_b
}
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");
--
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