From: Zheng Yejian <zhengyejian1@huawei.com>
To: <gregkh@linuxfoundation.org>, <lee.jones@linaro.org>,
<stable@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Cc: <tglx@linutronix.de>, <cj.chengjian@huawei.com>,
<judy.chenhui@huawei.com>, <zhangjinhao2@huawei.com>,
<nixiaoming@huawei.com>
Subject: [PATCH 4.4 3/3] futex: fix dead code in attach_to_pi_owner()
Date: Tue, 9 Mar 2021 11:06:05 +0800 [thread overview]
Message-ID: <20210309030605.3295183-4-zhengyejian1@huawei.com> (raw)
In-Reply-To: <20210309030605.3295183-1-zhengyejian1@huawei.com>
From: Thomas Gleixner <tglx@linutronix.de>
The handle_exit_race() function is defined in commit 9c3f39860367
("futex: Cure exit race"), which never returns -EBUSY. This results
in a small piece of dead code in the attach_to_pi_owner() function:
int ret = handle_exit_race(uaddr, uval, p); /* Never return -EBUSY */
...
if (ret == -EBUSY)
*exiting = p; /* dead code */
The return value -EBUSY is added to handle_exit_race() in upsteam
commit ac31c7ff8624409 ("futex: Provide distinct return value when
owner is exiting"). This commit was incorporated into v4.9.255, before
the function handle_exit_race() was introduced, whitout Modify
handle_exit_race().
To fix dead code, extract the change of handle_exit_race() from
commit ac31c7ff8624409 ("futex: Provide distinct return value when owner
is exiting"), re-incorporated.
Lee writes:
This commit takes the remaining functional snippet of:
ac31c7ff8624409 ("futex: Provide distinct return value when owner is exiting")
... and is the correct fix for this issue.
Fixes: 9c3f39860367 ("futex: Cure exit race")
Cc: stable@vger.kernel.org # v4.9.258
Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com>
Reviewed-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
---
kernel/futex.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index 116766ef7de6..98c65b3c3a00 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1202,11 +1202,11 @@ static int handle_exit_race(u32 __user *uaddr, u32 uval,
u32 uval2;
/*
- * If the futex exit state is not yet FUTEX_STATE_DEAD, wait
- * for it to finish.
+ * If the futex exit state is not yet FUTEX_STATE_DEAD, tell the
+ * caller that the alleged owner is busy.
*/
if (tsk && tsk->futex_state != FUTEX_STATE_DEAD)
- return -EAGAIN;
+ return -EBUSY;
/*
* Reread the user space value to handle the following situation:
--
2.25.4
next prev parent reply other threads:[~2021-03-09 3:00 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-09 3:06 [PATCH 4.4 0/3] Backport patch series to update Futex from 4.9 Zheng Yejian
2021-03-09 3:06 ` [PATCH 4.4 1/3] futex: Change locking rules Zheng Yejian
2021-03-09 10:40 ` Greg KH
2021-03-09 3:06 ` [PATCH 4.4 2/3] futex: Cure exit race Zheng Yejian
2021-03-09 3:06 ` Zheng Yejian [this message]
2021-03-09 10:40 ` [PATCH 4.4 3/3] futex: fix dead code in attach_to_pi_owner() Greg KH
2021-03-09 18:14 ` Lee Jones
2021-03-10 12:00 ` Greg KH
2021-03-10 13:28 ` Lee Jones
2021-03-10 14:10 ` Greg KH
2021-03-11 1:39 ` Zhengyejian (Zetta)
2021-03-09 10:41 ` [PATCH 4.4 0/3] Backport patch series to update Futex from 4.9 Greg KH
2021-03-11 3:48 ` Zhengyejian (Zetta)
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