linux-kernel - [PATCH 5.14 095/169] ucounts: Proper error handling in set_cred

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Date:   Mon, 25 Oct 2021 21:14:36 +0200
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 5.14 095/169] ucounts: Proper error handling in set_cred_ucounts

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

commit 34dc2fd6e6908499b669c7b45320cddf38b332e1 upstream.

Instead of leaking the ucounts in new if alloc_ucounts fails, store
the result of alloc_ucounts into a temporary variable, which is later
assigned to new->ucounts.

Cc: stable@...r.kernel.org
Fixes: 905ae01c4ae2 ("Add a reference to ucounts for each cred")
Link: https://lkml.kernel.org/r/87pms2s0v8.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, 3 insertions(+), 2 deletions(-)

--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -667,7 +667,7 @@ int set_cred_ucounts(struct cred *new)
 {
 	struct task_struct *task = current;
 	const struct cred *old = task->real_cred;
-	struct ucounts *old_ucounts = new->ucounts;
+	struct ucounts *new_ucounts, *old_ucounts = new->ucounts;
 
 	if (new->user == old->user && new->user_ns == old->user_ns)
 		return 0;
@@ -679,9 +679,10 @@ int set_cred_ucounts(struct cred *new)
 	if (old_ucounts && 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)))
+	if (!(new_ucounts = alloc_ucounts(new->user_ns, new->euid)))
 		return -EAGAIN;
 
+	new->ucounts = new_ucounts;
 	if (old_ucounts)
 		put_ucounts(old_ucounts);