linux-kernel - [PATCH 5.15 179/196] ucounts: In set_cred_ucounts assume new->ucounts is non-NULL

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Date:   Mon, 21 Feb 2022 09:50:11 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Yu Zhao <yuzhao@...gle.com>,
        Alexey Gladkov <legion@...nel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 5.15 179/196] ucounts: In set_cred_ucounts assume new->ucounts is non-NULL

From: Eric W. Biederman <ebiederm@...ssion.com>

commit 99c31f9feda41d0f10d030dc04ba106c93295aa2 upstream.

Any cred that is destined for use by commit_creds must have a non-NULL
cred->ucounts field.  Only curing credential construction is a NULL
cred->ucounts valid.  Only abort_creds, put_cred, and put_cred_rcu
needs to deal with a cred with a NULL ucount.  As set_cred_ucounts is
non of those case don't confuse people by handling something that can
not happen.

Link: https://lkml.kernel.org/r/871r4irzds.fsf_-_@disp2133
Tested-by: Yu Zhao <yuzhao@...gle.com>
Reviewed-by: Alexey Gladkov <legion@...nel.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/cred.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -676,15 +676,14 @@ int set_cred_ucounts(struct cred *new)
 	 * This optimization is needed because alloc_ucounts() uses locks
 	 * for table lookups.
 	 */
-	if (old_ucounts && old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->euid))
+	if (old_ucounts->ns == new->user_ns && uid_eq(old_ucounts->uid, new->euid))
 		return 0;
 
 	if (!(new_ucounts = alloc_ucounts(new->user_ns, new->euid)))
 		return -EAGAIN;
 
 	new->ucounts = new_ucounts;
-	if (old_ucounts)
-		put_ucounts(old_ucounts);
+	put_ucounts(old_ucounts);
 
 	return 0;
 }