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 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
netfilter-drop-outermost-socket-lock-in-getsockopt.patch
and it can be found in the queue-4.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 01ea306f2ac2baff98d472da719193e738759d93 Mon Sep 17 00:00:00 2001
From: Paolo Abeni <pabeni@xxxxxxxxxx>
Date: Thu, 8 Feb 2018 12:19:00 +0100
Subject: netfilter: drop outermost socket lock in getsockopt()
From: Paolo Abeni <pabeni@xxxxxxxxxx>
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@xxxxxxxxx>
======================================================
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@xxxxxxxxxxxxxxxxxxxxxxxxx
Suggested-by: Florian Westphal <fw@xxxxxxxxx>
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -1563,10 +1563,7 @@ 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;
@@ -1598,9 +1595,7 @@ 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
@@ -1367,10 +1367,7 @@ 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);
}
@@ -1409,10 +1406,7 @@ 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@xxxxxxxxxx are
queue-4.15/netfilter-drop-outermost-socket-lock-in-getsockopt.patch