From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xin Long Subject: Re: [PATCH net] netfilter: on setsockopt() acquire sock lock only in the required scope Date: Thu, 8 Feb 2018 19:04:45 +0800 Message-ID: References: <0faf65d7a9b102fbe107d1bb75b5d97e4622ee3e.1518084409.git.pabeni@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: network dev , "David S. Miller" , Florian Westphal , netfilter-devel@vger.kernel.org To: Paolo Abeni Return-path: Received: from mail-qk0-f194.google.com ([209.85.220.194]:34074 "EHLO mail-qk0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750806AbeBHLEq (ORCPT ); Thu, 8 Feb 2018 06:04:46 -0500 In-Reply-To: <0faf65d7a9b102fbe107d1bb75b5d97e4622ee3e.1518084409.git.pabeni@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, Feb 8, 2018 at 6:38 PM, Paolo Abeni wrote: > The Syzbot reported a possible deadlock in the netfilter area caused by > rtnl lock, xt lock and socket lock being acquired with a different order > on different code paths, leading to the following backtrace: > > ====================================================== > WARNING: possible circular locking dependency detected > 4.15.0+ #301 Not tainted > ------------------------------------------------------ > syzkaller233489/4179 is trying to acquire lock: > (rtnl_mutex){+.+.}, at: [<0000000048e996fd>] rtnl_lock+0x17/0x20 > net/core/rtnetlink.c:74 > > but task is already holding lock: > (&xt[i].mutex){+.+.}, at: [<00000000328553a2>] > xt_find_table_lock+0x3e/0x3e0 net/netfilter/x_tables.c:1041 > > which lock already depends on the new lock. > === > > Since commit 3f34cfae1230 ("netfilter: on sockopt() acquire sock lock > only in the required scope"), we already acquire the socket lock in > the innermost scope, where needed. In such commit I forgot to remove > the outer-most socket lock from the getsockopt() path, this commit > addresses the issues dropping it now. > > Fixes: 202f59afd441 ("netfilter: ipt_CLUSTERIP: do not hold dev") > Fixes: 3f34cfae1230 ("netfilter: on sockopt() acquire sock lock only in the required scope") > Reported-by: syzbot+ddde1c7b7ff7442d7f2d@syzkaller.appspotmail.com > Suggested-by: Florian Westphal > Signed-off-by: Paolo Abeni > --- > net/ipv4/ip_sockglue.c | 7 +------ > net/ipv6/ipv6_sockglue.c | 10 ++-------- > 2 files changed, 3 insertions(+), 14 deletions(-) > > diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c > index 008be04ac1cc..9c41a0cef1a5 100644 > --- a/net/ipv4/ip_sockglue.c > +++ b/net/ipv4/ip_sockglue.c > @@ -1567,10 +1567,7 @@ int ip_getsockopt(struct sock *sk, int level, > if (get_user(len, optlen)) > return -EFAULT; > > - lock_sock(sk); > - err = nf_getsockopt(sk, PF_INET, optname, optval, > - &len); > - release_sock(sk); > + err = nf_getsockopt(sk, PF_INET, optname, optval, &len); > if (err >= 0) > err = put_user(len, optlen); > return err; > @@ -1602,9 +1599,7 @@ int compat_ip_getsockopt(struct sock *sk, int level, int optname, > if (get_user(len, optlen)) > return -EFAULT; > > - lock_sock(sk); > err = compat_nf_getsockopt(sk, PF_INET, optname, optval, &len); > - release_sock(sk); > if (err >= 0) > err = put_user(len, optlen); > return err; > diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c > index d78d41fc4b1a..24535169663d 100644 > --- a/net/ipv6/ipv6_sockglue.c > +++ b/net/ipv6/ipv6_sockglue.c > @@ -1367,10 +1367,7 @@ int ipv6_getsockopt(struct sock *sk, int level, int optname, > if (get_user(len, optlen)) > return -EFAULT; > > - lock_sock(sk); > - err = nf_getsockopt(sk, PF_INET6, optname, optval, > - &len); > - release_sock(sk); > + err = nf_getsockopt(sk, PF_INET6, optname, optval, &len); > if (err >= 0) > err = put_user(len, optlen); > } > @@ -1409,10 +1406,7 @@ int compat_ipv6_getsockopt(struct sock *sk, int level, int optname, > if (get_user(len, optlen)) > return -EFAULT; > > - lock_sock(sk); > - err = compat_nf_getsockopt(sk, PF_INET6, > - optname, optval, &len); > - release_sock(sk); > + err = compat_nf_getsockopt(sk, PF_INET6, optname, optval, &len); > if (err >= 0) > err = put_user(len, optlen); > } > -- > 2.14.3 > Patch looks good to me, the better way to fix this deadlock, just the subject should be 'getsockopt' instead. Thanks.