From 96f3135d3e5d3921c8b6eb9bf0f841ec4457f8b5 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 11 Mar 2021 11:26:00 +0800 Subject: futex: fix dead code in attach_to_pi_owner() This patch comes directly from an origin patch (commit 91509e84949fc97e7424521c32a9e227746e0b85) in v4.9. And it is part of a full patch which was originally back-ported to v4.14 as commit e6e00df182908f34360c3c9f2d13cc719362e9c0 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 Reviewed-by: Lee Jones Signed-off-by: Greg Kroah-Hartman Signed-off-by: Zheng Yejian Signed-off-by: Greg Kroah-Hartman --- kernel/futex.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/futex.c b/kernel/futex.c index 4894c0934205..ff5499b0c5b3 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1204,11 +1204,11 @@ 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: -- cgit v1.2.3