Re: [bug report] ovl: copy up of disconnected dentries

[Amir Goldstein <amir73il@xxxxxxxxx>]

On Mon, Mar 22, 2021 at 2:18 PM Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>
> Hello Amir Goldstein,
>
> The patch aa3ff3c152ff: "ovl: copy up of disconnected dentries" from
> Oct 15, 2017, leads to the following static checker warning:

Heh! that's fashionably late :)

>
>         fs/overlayfs/copy_up.c:972 ovl_copy_up_flags()
>         warn: 'old_cred' not released on lines: 944.
>
> fs/overlayfs/copy_up.c
>    932  static int ovl_copy_up_flags(struct dentry *dentry, int flags)
>    933  {
>    934          int err = 0;
>    935          const struct cred *old_cred = ovl_override_creds(dentry->d_sb);
>    936          bool disconnected = (dentry->d_flags & DCACHE_DISCONNECTED);
>    937
>    938          /*
>    939           * With NFS export, copy up can get called for a disconnected non-dir.
>    940           * In this case, we will copy up lower inode to index dir without
>    941           * linking it to upper dir.
>    942           */
>    943          if (WARN_ON(disconnected && d_is_dir(dentry)))
>    944                  return -EIO;
>
> Should this call revert_creds(old_cred); before returning?

Yes. Here's a simple fix, care to post it?

Thanks,
Amir.

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 0b2891c6c71e..2846b943e80c 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -932,7 +932,7 @@ static int ovl_copy_up_one(struct dentry *parent,
struct dentry *dentry,
 static int ovl_copy_up_flags(struct dentry *dentry, int flags)
 {
        int err = 0;
-       const struct cred *old_cred = ovl_override_creds(dentry->d_sb);
+       const struct cred *old_cred;
        bool disconnected = (dentry->d_flags & DCACHE_DISCONNECTED);

        /*
@@ -943,6 +943,7 @@ static int ovl_copy_up_flags(struct dentry
*dentry, int flags)
        if (WARN_ON(disconnected && d_is_dir(dentry)))
                return -EIO;

+       old_cred = ovl_override_creds(dentry->d_sb);
        while (!err) {
                struct dentry *next;
                struct dentry *parent = NULL;