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Message-ID: <CAMbhsRQf1QJHRJH+Mc8dLkU5i_V+SCAv=ADM+AawywG+14zgtg@mail.gmail.com>
Date: Tue, 8 Sep 2026 13:56:14 -0700
From: Colin Cross <ccross@...roid.com>
To: musl@...ts.openwall.com
Subject: Re: Fix deadlock in timer_create when syscall fails
On Sun, Sep 6, 2026 at 11:57 AM Alexey Izbyshev <izbyshev@...ras.ru> wrote:
>
> On 2026-09-03 10:00, Szabolcs Nagy wrote:
> >
> > it seems
> >
> > commit 3ad3fa962efee12067d68c3405a537dce156a7ac
> > fix thread leak on timer_create(SIGEV_THREAD) failure
> >
> > (ab)used self->cancel to mark timer_create failures, because
> > the obvious self->timer_id < 0 can also mean deleted timer.
> > then
> >
> > commit cde213f9c3ac1aa168581222edee6a6642113323
> > timer_create: replace pthread barrier with semaphores for thread
> > start
> >
> > changed the sync to two sems, introducing the cancel deadlock,
>
> and other issues:
> * sem_wait call now clobbers errno set by timer_create.
> * if sem_wait is cancelled, the timer and its thread are leaked, and the
> thread may also access args past its lifetime.
I've attached v3 that fixes these two issues as well by disabling
cancellation around the semaphore operations in the parent thread and
saving the return value of SYS_timer_create.
Download attachment "0001-SIGEV_THREAD-timers-fix-deadlock-when-timer_create-s.patch" of type "application/x-patch" (3687 bytes)
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