linux-kernel - [PATCH] sched: core: remove access_ok() before copy_to

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Message-Id: <20220815142137.29982-1-91tuocao@gmail.com>
Date:   Mon, 15 Aug 2022 22:21:37 +0800
From:   Tuo Cao <91tuocao@...il.com>
To:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org
Cc:     dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
        linux-kernel@...r.kernel.org, 91tuocao@...il.com
Subject: [PATCH] sched: core: remove access_ok() before copy_to_user()

If usize > ksize, usize may be not valid and if(!access_ok()) will return
-EFAULT. But ksize may be valid, copy_to_user() should be executed.And
also, copy_to_user() will calls access_ok() to test whether a block of
memory is a valid user space address.

Signed-off-by: Tuo Cao <91tuocao@...il.com>
---
 kernel/sched/core.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ee28253c9ac0..fe6a65a54626 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7975,9 +7975,6 @@ sched_attr_copy_to_user(struct sched_attr __user *uattr,
 {
 	unsigned int ksize = sizeof(*kattr);
 
-	if (!access_ok(uattr, usize))
-		return -EFAULT;
-
 	/*
 	 * sched_getattr() ABI forwards and backwards compatibility:
 	 *
-- 
2.17.1