From: Rich Felker <dalias@libc.org>
To: Alexey Izbyshev <izbyshev@ispras.ru>
Cc: musl@lists.openwall.com
Subject: Re: [musl] Potentially infinite loop in posix_spawn'ed child
Date: Mon, 24 May 2021 16:33:30 -0400 [thread overview]
Message-ID: <20210524203329.GB2546@brightrain.aerifal.cx> (raw)
In-Reply-To: <985e15962c164eb3076752d6ee4c05fe@ispras.ru>
On Mon, May 24, 2021 at 01:09:21PM +0300, Alexey Izbyshev wrote:
> Hi,
>
> I've noticed the following loop at https://git.musl-libc.org/cgit/musl/tree/src/process/posix_spawn.c#n159:
>
> exec(args->path, args->argv, args->envp);
> ret = -errno;
>
> fail:
> /* Since sizeof errno < PIPE_BUF, the write is atomic. */
> ret = -ret;
> if (ret) while (__syscall(SYS_write, p, &ret, sizeof ret) < 0);
> _exit(127);
>
> Is there any reason that write is done in a loop? If SIGPIPE is
> blocked or ignored and the parent dies before this point, the child
> will spin in it forever.
I suppose the special case of EPIPE should be considered here as no
need to inform the parent. Are there any other errors that should be
treated specially?
> A test case is attached. It overrides execve() to abuse it as a
> callback, avoiding reliance on timings.
As noted that's undefined but it's completely reasonable as a way to
do the testing. Using seccomp to make the parent die might be slightly
less hackish but it doesn't matter. Thanks for the report.
Rich
next prev parent reply other threads:[~2021-05-24 20:33 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-24 10:09 Alexey Izbyshev
2021-05-24 15:40 ` Szabolcs Nagy
2021-05-24 16:50 ` Alexey Izbyshev
2021-05-24 20:33 ` Rich Felker [this message]
2021-05-25 6:30 ` Alexey Izbyshev
2021-05-25 14:32 ` Rich Felker
2024-02-29 14:03 ` Alexey Izbyshev
2024-02-29 15:35 ` Rich Felker
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