linux-kernel - [PATCH v2 21/29] smb: avoid pointless cred reference count bump

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Message-Id: <20241125-work-cred-v2-21-68b9d38bb5b2@kernel.org>
Date: Mon, 25 Nov 2024 15:10:17 +0100
From: Christian Brauner <brauner@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Amir Goldstein <amir73il@...il.com>, Miklos Szeredi <miklos@...redi.hu>, 
 Al Viro <viro@...iv.linux.org.uk>, Jens Axboe <axboe@...nel.dk>, 
 linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
 Christian Brauner <brauner@...nel.org>
Subject: [PATCH v2 21/29] smb: avoid pointless cred reference count bump

The creds are allocated via prepare_kernel_cred() which has already
taken a reference.

This also removes a pointless check that gives the impression that
override_creds() can ever be called on a task with current->cred NULL.
That's not possible afaict. Remove the check to not imply that there can
be a dangling pointer in current->cred.

Signed-off-by: Christian Brauner <brauner@...nel.org>
---
 fs/smb/server/smb_common.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/fs/smb/server/smb_common.c b/fs/smb/server/smb_common.c
index f1d770a214c8b2c7d7dd4083ef57c7130bbce52c..a92e3081cead250dac89a0dc00fcee8444465b8a 100644
--- a/fs/smb/server/smb_common.c
+++ b/fs/smb/server/smb_common.c
@@ -780,11 +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));
-	if (!work->saved_cred) {
-		abort_creds(cred);
-		return -EINVAL;
-	}
+	work->saved_cred = override_creds(cred);
 	return 0;
 }
 
@@ -796,13 +792,11 @@ int ksmbd_override_fsids(struct ksmbd_work *work)
 void ksmbd_revert_fsids(struct ksmbd_work *work)
 {
 	const struct cred *cred;
-
 	WARN_ON(!work->saved_cred);
 
-	cred = current_cred();
-	put_cred(revert_creds(work->saved_cred));
-	put_cred(cred);
+	cred = revert_creds(work->saved_cred);
 	work->saved_cred = NULL;
+	put_cred(cred);
 }
 
 __le32 smb_map_generic_desired_access(__le32 daccess)

-- 
2.45.2