| Message ID | 20210224100923.51315-1-nixiaoming@huawei.com |
|---|---|
| State | New |
| Headers | show |
| Series | [4.9.258] futex: fix dead code in attach_to_pi_owner() | expand |
On Wed, 24 Feb 2021, Xiaoming Ni wrote: > 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. > > Fixes: 9c3f39860367 ("futex: Cure exit race") > Cc: stable@vger.kernel.org # v4.9.258 > Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com> > --- > kernel/futex.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) To clarify, this is not a wholesale back-port from Mainline. It takes the remaining functional snippet of: ac31c7ff8624409 ("futex: Provide distinct return value when owner is exiting") ... and is the correct fix for this issue. Reviewed-by: Lee Jones <lee.jones@linaro.org> > diff --git a/kernel/futex.c b/kernel/futex.c > index b65dbb5d60bb..0fd785410150 100644 > --- a/kernel/futex.c > +++ b/kernel/futex.c > @@ -1207,11 +1207,11 @@ 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:
On Thu, Feb 25, 2021 at 09:17:38AM +0000, Lee Jones wrote: > On Wed, 24 Feb 2021, Xiaoming Ni wrote: > > > 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. > > > > Fixes: 9c3f39860367 ("futex: Cure exit race") > > Cc: stable@vger.kernel.org # v4.9.258 > > Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com> > > --- > > kernel/futex.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > To clarify, this is not a wholesale back-port from Mainline. > > It takes the remaining functional snippet of: > > ac31c7ff8624409 ("futex: Provide distinct return value when owner is exiting") > > ... and is the correct fix for this issue. > > Reviewed-by: Lee Jones <lee.jones@linaro.org> Thanks, now queued up. greg k-h
diff --git a/kernel/futex.c b/kernel/futex.c index b65dbb5d60bb..0fd785410150 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1207,11 +1207,11 @@ 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:
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. Fixes: 9c3f39860367 ("futex: Cure exit race") Cc: stable@vger.kernel.org # v4.9.258 Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com> --- kernel/futex.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)