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Date: Sun, 12 Feb 2023 22:35:39 +0300
From: Alexey Izbyshev <izbyshev@...ras.ru>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] mq_notify: fix close/recv race on failure path
On 2023-02-12 21:23, Alexey Izbyshev wrote:
> On 2023-02-12 03:32, Rich Felker wrote:
> diff --git a/src/mq/mq_notify.c b/src/mq/mq_notify.c
> index a42888d2..8eac71ed 100644
> --- a/src/mq/mq_notify.c
> +++ b/src/mq/mq_notify.c
> @@ -10,6 +10,8 @@
> struct args {
> sem_t sem;
> int sock;
> + mqd_t mqd;
> + int err;
> const struct sigevent *sev;
> };
>
> @@ -21,8 +23,21 @@ static void *start(void *p)
> int s = args->sock;
> void (*func)(union sigval) = args->sev->sigev_notify_function;
> union sigval val = args->sev->sigev_value;
> + struct sigevent sev2;
> + static const char zeros[32];
> + int err = 0;
>
> + sev2.sigev_notify = SIGEV_THREAD;
> + sev2.sigev_signo = s;
> + sev2.sigev_value.sival_ptr = (void *)&zeros;
> +
> + err = 0;
>
> This assignment is redundant.
>
> Maybe this hunk could be simplified by getting rid of err and simply
> doing "args->err = -__syscall(SYS_mq_notify, args->mqd, &sev2)".
>
Never mind, err is needed because we can't access args->err after
sem_post.
Alexey
> Except for this nit, the patches look good to me, thanks!
>
> Alexey
>
> + if (syscall(SYS_mq_notify, args->mqd, &sev2) < 0)
> + err = errno;
> + args->err = err;
> sem_post(&args->sem);
> + if (err) return 0;
> +
> n = recv(s, buf, sizeof(buf), MSG_NOSIGNAL|MSG_WAITALL);
> close(s);
> if (n==sizeof buf && buf[sizeof buf - 1] == 1)
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