linux-kernel - [PATCH v4 3/3] binder: use euid from cred instead of using task

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Message-Id: <20211007004629.1113572-4-tkjos@google.com>
Date:   Wed,  6 Oct 2021 17:46:29 -0700
From:   Todd Kjos <tkjos@...gle.com>
To:     gregkh@...uxfoundation.org, arve@...roid.com, tkjos@...roid.com,
        maco@...roid.com, christian@...uner.io, jmorris@...ei.org,
        serge@...lyn.com, paul@...l-moore.com,
        stephen.smalley.work@...il.com, eparis@...isplace.org,
        keescook@...omium.org, jannh@...gle.com, jeffv@...gle.com,
        zohar@...ux.ibm.com, linux-security-module@...r.kernel.org,
        selinux@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Cc:     joel@...lfernandes.org, kernel-team@...roid.com,
        Todd Kjos <tkjos@...gle.com>, stable@...r.kernel.org
Subject: [PATCH v4 3/3] binder: use euid from cred instead of using task

Set a transaction's sender_euid from the 'struct cred'
saved at binder_open() instead of looking up the euid
from the binder proc's 'struct task'. This ensures
the euid is associated with the security context that
of the task that opened binder.

Fixes: 457b9a6f09f0 ("Staging: android: add binder driver")
Signed-off-by: Todd Kjos <tkjos@...gle.com>
Suggested-by: Stephen Smalley <stephen.smalley.work@...il.com>
Cc: stable@...r.kernel.org # 4.4+
---
v3: added this patch to series

 drivers/android/binder.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 989afd0804ca..26382e982c5e 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2711,7 +2711,7 @@ static void binder_transaction(struct binder_proc *proc,
 		t->from = thread;
 	else
 		t->from = NULL;
-	t->sender_euid = task_euid(proc->tsk);
+	t->sender_euid = proc->cred->euid;
 	t->to_proc = target_proc;
 	t->to_thread = target_thread;
 	t->code = tr->code;
-- 
2.33.0.800.g4c38ced690-goog