lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Tue, 1 Jan 2013 21:17:28 +0000 From: Eric Wong <normalperson@...t.net> To: Eric Dumazet <eric.dumazet@...il.com> Cc: linux-kernel@...r.kernel.org, Hans Verkuil <hans.verkuil@...co.com>, Jiri Olsa <jolsa@...hat.com>, Jonathan Corbet <corbet@....net>, Al Viro <viro@...iv.linux.org.uk>, Davide Libenzi <davidel@...ilserver.org>, Hans de Goede <hdegoede@...hat.com>, Mauro Carvalho Chehab <mchehab@...radead.org>, David Miller <davem@...emloft.net>, Andrew Morton <akpm@...ux-foundation.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Andreas Voellmy <andreas.voellmy@...e.edu>, "Junchang(Jason) Wang" <junchang.wang@...e.edu>, netdev@...r.kernel.org, linux-fsdevel@...r.kernel.org Subject: Re: [PATCH] poll: prevent missed events if _qproc is NULL Eric Wong <normalperson@...t.net> wrote: > Eric Dumazet <eric.dumazet@...il.com> wrote: > > commit 626cf236608505d376e4799adb4f7eb00a8594af should not have this > > side effect, at least for poll()/select() functions. The epoll() changes > > I am not yet very confident. > > I have a better explanation of the epoll problem below. > > An alternate version (limited to epoll) would be: > > diff --git a/fs/eventpoll.c b/fs/eventpoll.c > index cd96649..ca5f3d0 100644 > --- a/fs/eventpoll.c > +++ b/fs/eventpoll.c > @@ -1299,6 +1299,7 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even > * Get current event bits. We can safely use the file* here because > * its usage count has been increased by the caller of this function. > */ > + smp_mb(); > revents = epi->ffd.file->f_op->poll(epi->ffd.file, &pt); > > /* > > > I suspect a race already existed before this commit, it would be nice to > > track it properly. > > I don't believe this race existed before that change. I was wrong, rereading 626cf236608505d376e4799adb4f7eb00a8594af, I think this race existed before. Perhaps my alternate patch above is a better fix. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists