This is a note to let you know that I've just added the patch titled
netfilter: drop outermost socket lock in getsockopt()
to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: netfilter-drop-outermost-socket-lock-in-getsockopt.patch and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 01ea306f2ac2baff98d472da719193e738759d93 Mon Sep 17 00:00:00 2001
From: Paolo Abeni pabeni@redhat.com Date: Thu, 8 Feb 2018 12:19:00 +0100 Subject: netfilter: drop outermost socket lock in getsockopt()
From: Paolo Abeni pabeni@redhat.com
commit 01ea306f2ac2baff98d472da719193e738759d93 upstream.
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: Reviewed-by: Xin Long lucien.xin@gmail.com
====================================================== 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.
v1 -> v2: fix bad subj, added relavant 'fixes' tag
Fixes: 22265a5c3c10 ("netfilter: xt_TEE: resolve oif using netdevice notifiers") 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 fw@strlen.de Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/ipv4/ip_sockglue.c | 7 +------ net/ipv6/ipv6_sockglue.c | 10 ++-------- 2 files changed, 3 insertions(+), 14 deletions(-)
--- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -1527,10 +1527,7 @@ int ip_getsockopt(struct sock *sk, int l 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; @@ -1562,9 +1559,7 @@ int compat_ip_getsockopt(struct sock *sk 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; --- a/net/ipv6/ipv6_sockglue.c +++ b/net/ipv6/ipv6_sockglue.c @@ -1340,10 +1340,7 @@ int ipv6_getsockopt(struct sock *sk, int 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); } @@ -1382,10 +1379,7 @@ int compat_ipv6_getsockopt(struct sock * 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); }
Patches currently in stable-queue which might be from pabeni@redhat.com are
queue-4.4/netfilter-drop-outermost-socket-lock-in-getsockopt.patch