From: Rich Felker <dalias@libc.org>
To: musl@lists.openwall.com
Subject: Re: [PATCH] fix deadlock in synccall after threaded fork
Date: Mon, 1 Jul 2019 10:12:02 -0400 [thread overview]
Message-ID: <20190701141202.GQ1506@brightrain.aerifal.cx> (raw)
In-Reply-To: <20190701034428.62764-1-samuel@sholland.org>
On Sun, Jun 30, 2019 at 10:44:28PM -0500, Samuel Holland wrote:
> synccall may be called by AS-safe functions such as setuid/setgid after
> fork. although fork() resets libc.threads_minus_one, causing synccall to
> take the single-threaded path, synccall still takes the thread list
> lock. This lock may be held by another thread if for example fork()
> races with pthread_create(). After fork(), the value of the lock is
> meaningless, so clear it.
> ---
> src/process/fork.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/src/process/fork.c b/src/process/fork.c
> index 11286ef4..fb42478a 100644
> --- a/src/process/fork.c
> +++ b/src/process/fork.c
> @@ -28,6 +28,7 @@ pid_t fork(void)
> self->robust_list.off = 0;
> self->robust_list.pending = 0;
> self->next = self->prev = self;
> + __thread_list_lock = 0;
> libc.threads_minus_1 = 0;
> }
> __restore_sigs(&set);
> --
> 2.21.0
Thanks! Committing this with a maintainer's note referencing the
commits that caused the regression and a further remark on why it's
safe/correct to make this change.
Rich
prev parent reply other threads:[~2019-07-01 14:12 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-01 3:44 Samuel Holland
2019-07-01 14:12 ` Rich Felker [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190701141202.GQ1506@brightrain.aerifal.cx \
--to=dalias@libc.org \
--cc=musl@lists.openwall.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/musl/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).