Re: [PATCH 21/26] smb: avoid pointless cred reference count bump

From: Christian Brauner
Date: Mon Nov 25 2024 - 07:25:53 EST


On Sun, Nov 24, 2024 at 06:37:43PM +0000, Al Viro wrote:
> On Sun, Nov 24, 2024 at 02:44:07PM +0100, Christian Brauner wrote:
> > No need for the extra reference count bump.
> >
> > Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
> > ---
> > fs/smb/server/smb_common.c | 4 +---
> > 1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/fs/smb/server/smb_common.c b/fs/smb/server/smb_common.c
> > index f1d770a214c8b2c7d7dd4083ef57c7130bbce52c..a3f96804f84f03c22376769dffdf60cd66f5e3d2 100644
> > --- a/fs/smb/server/smb_common.c
> > +++ b/fs/smb/server/smb_common.c
> > @@ -780,7 +780,7 @@ int __ksmbd_override_fsids(struct ksmbd_work *work,
> > cred->cap_effective = cap_drop_fs_set(cred->cap_effective);
> >
> > WARN_ON(work->saved_cred);
> > - work->saved_cred = override_creds(get_new_cred(cred));
> > + work->saved_cred = override_creds(cred);
> > if (!work->saved_cred) {
> > abort_creds(cred);
> > return -EINVAL;
>
> Won't that leave a dangling pointer?

Afaict, the whole check doesn't make sense because I don't see how
override_creds() could be called on a task with current->cred == NULL.
There's no way to opt out of having current->cred set.