linux-kernel - [PATCH 1/4] ucounts: In set_cred_ucounts assume new->ucounts is non-NULL

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Date:   Mon, 18 Oct 2021 12:55:43 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Alexey Gladkov <legion@...nel.org>
Cc:     Rune Kleveland <rune.kleveland@...omedia.dk>,
        Yu Zhao <yuzhao@...gle.com>,
        Jordan Glover <Golden_Miller83@...tonmail.ch>,
        LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        containers@...ts.linux-foundation.org,
        Hillf Danton <hdanton@...a.com>
Subject: [PATCH 1/4] ucounts: In set_cred_ucounts assume new->ucounts is non-NULL


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.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 kernel/cred.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/cred.c b/kernel/cred.c
index 1ae0b4948a5a..473d17c431f3 100644
--- 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;
 }
-- 
2.20.1