diff mbox series

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

Message ID 20241124-work-cred-v1-21-f352241c3970@kernel.org (mailing list archive)
State New
Headers show
Series [01/26] tree-wide: s/override_creds()/override_creds_light(get_new_cred())/g | expand

Commit Message

Christian Brauner Nov. 24, 2024, 1:44 p.m. UTC 
No need for the extra reference count bump.

Signed-off-by: Christian Brauner <brauner@kernel.org>
---
 fs/smb/server/smb_common.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

Comments

Al Viro Nov. 24, 2024, 6:37 p.m. UTC | #1 
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@kernel.org>
> ---
>  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?
Christian Brauner Nov. 25, 2024, 11:22 a.m. UTC | #2 
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@kernel.org>
> > ---
> >  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.
diff mbox series

Patch

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;
@@ -799,9 +799,7 @@  void ksmbd_revert_fsids(struct ksmbd_work *work)
 
 	WARN_ON(!work->saved_cred);
 
-	cred = current_cred();
 	put_cred(revert_creds(work->saved_cred));
-	put_cred(cred);
 	work->saved_cred = NULL;
 }