From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx # v4.9.258
Signed-off-by: Xiaoming Ni <nixiaoming@xxxxxxxxxx>
Reviewed-by: Lee Jones <lee.jones@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Zheng Yejian <zhengyejian1@xxxxxxxxxx>
---
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
