From: Al Viro <viro@zeniv.linux.org.uk>
To: Sasha Levin <sashal@kernel.org>
Cc: netdev@vger.kernel.org, David Miller <davem@davemloft.net>,
stable@kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH][unix] missing barriers in some of unix_sock ->addr and ->path accesses
Date: Mon, 18 Feb 2019 21:32:46 +0000 [thread overview]
Message-ID: <20190218213246.GV2217@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20190218211434.05DF121773@mail.kernel.org>
On Mon, Feb 18, 2019 at 09:14:33PM +0000, Sasha Levin wrote:
> Hi,
>
> [This is an automated email]
>
> This commit has been processed because it contains a -stable tag.
Ugh... Should've removed Cc; stable from netdev posting; my apologies.
> How should we proceed with this patch?
Wait for it to get into davem's tree, for starters?
Sorry about that, again...
FWIW, further adventures in net/unix land:
unix_dgram_poll() contains
/* connection hasn't started yet? */
if (sk->sk_state == TCP_SYN_SENT)
return mask;
and nothing in there sets TCP_SYN_SENT state (not that it would've made
any sense of AF_UNIX).
unix_poll() contains
/* Connection-based need to check for termination and startup */
if ((sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET) &&
sk->sk_state == TCP_CLOSE)
while it can only be called as ->poll of unix_stream_ops, which means
that sk->sk_type can't be anything other that SOCK_STREAM in there.
static void scan_children(struct sock *x, void (*func)(struct unix_sock *),
struct sk_buff_head *hitlist)
{
if (x->sk_state != TCP_LISTEN) {
scan_inflight(x, func, hitlist);
} else {
...
has no exclusion or barriers to deal with the store of TCP_LISTEN into
->sk_state inside unix_listen(). That one's potentially nasty - we won't
find SCM_RIGHTS already queued to embrios in x's queue until we notice
that x->sk_state == TCP_LISTEN, which can happen between two calls of
scan_children() in the same unix_gc() run. The race is narrow, but not
impossible, AFAICS. Reasonably easy to fix - lift locking the queue
out of scan_inflight(), grab the queue lock before checking if it's
a listener and have unix_listen() either grab the queue lock around the
assignment to ->sk_state, or pump it up and down before dropping
unix_state_lock() (at which point connect() might be able to find it, etc.)
Al, still digging through net/unix...
next prev parent reply other threads:[~2019-02-18 21:32 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-15 20:09 [PATCH][unix] missing barriers in some of unix_sock ->addr and ->path accesses Al Viro
2019-02-18 21:14 ` Sasha Levin
2019-02-18 21:32 ` Al Viro [this message]
2019-02-19 1:30 ` Sasha Levin
2019-02-21 4:07 ` David Miller
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=20190218213246.GV2217@ZenIV.linux.org.uk \
--to=viro@zeniv.linux.org.uk \
--cc=davem@davemloft.net \
--cc=netdev@vger.kernel.org \
--cc=sashal@kernel.org \
--cc=stable@kernel.org \
--cc=stable@vger.kernel.org \
/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.
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).