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Patch "netlink: Fix autobind race condition that leads to zero port ID" has been added to the 4.1-stable tree

PATCH [email protected] 1 participant 1 message Sep 30, 2015

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This is a note to let you know that I've just added the patch titled

netlink: Fix autobind race condition that leads to zero port ID

to the 4.1-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:
netlink-fix-autobind-race-condition-that-leads-to-zero-port-id.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From foo@baz Wed Sep 30 05:22:23 CEST 2015

From: Herbert Xu <[email protected]>
Date: Fri, 18 Sep 2015 19:16:50 +0800
Subject: netlink: Fix autobind race condition that leads to zero port ID
Status: RO
Content-Length: 3101
Lines: 90

From: Herbert Xu <[email protected]>

[ Upstream commit 1f770c0a09da855a2b51af6d19de97fb955eca85 ]

The commit c0bb07df7d981e4091432754e30c9c720e2c0c78 ("netlink:
Reset portid after netlink_insert failure") introduced a race condition where if two threads try to autobind the same socket one of them may end up with a zero port ID. This led to kernel deadlocks that were observed by multiple people.

This patch reverts that commit and instead fixes it by introducing a separte rhash_portid variable so that the real portid is only set after the socket has been successfully hashed.

Fixes c0bb07df7d98 ("netlink: Reset portid after netlink_insert failure")
Reported-by Tejun Heo <[email protected]>
Reported-by Linus Torvalds <[email protected]>
Signed-off-by Herbert Xu <[email protected]>
Signed-off-by David S. Miller <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 net/netlink/af_netlink.c |   11 ++++++-----
 net/netlink/af_netlink.h |    1 +
 2 files changed, 7 insertions(+), 5 deletions(-)
net/netlink/af_netlink.c +6 -5
@@ -1017,7 +1017,7 @@ static inline int netlink_compare(struct
 	const struct netlink_compare_arg *x = arg->key;
 	const struct netlink_sock *nlk = ptr;
 
-	return nlk->portid != x->portid ||
+	return nlk->rhash_portid != x->portid ||
 	       !net_eq(sock_net(&nlk->sk), read_pnet(&x->pnet));
 }
 

@@ -1043,7 +1043,7 @@ static int __netlink_insert(struct netli
 {
 	struct netlink_compare_arg arg;
 
-	netlink_compare_arg_init(&arg, sock_net(sk), nlk_sk(sk)->portid);
+	netlink_compare_arg_init(&arg, sock_net(sk), nlk_sk(sk)->rhash_portid);
 	return rhashtable_lookup_insert_key(&table->hash, &arg,
 					    &nlk_sk(sk)->node,
 					    netlink_rhashtable_params);

@@ -1105,7 +1105,7 @@ static int netlink_insert(struct sock *s
 	    unlikely(atomic_read(&table->hash.nelems) >= UINT_MAX))
 		goto err;
 
-	nlk_sk(sk)->portid = portid;
+	nlk_sk(sk)->rhash_portid = portid;
 	sock_hold(sk);
 
 	err = __netlink_insert(table, sk);

@@ -1117,10 +1117,11 @@ static int netlink_insert(struct sock *s
 			err = -EOVERFLOW;
 		if (err == -EEXIST)
 			err = -EADDRINUSE;
-		nlk_sk(sk)->portid = 0;
 		sock_put(sk);
 	}
 
+	nlk_sk(sk)->portid = portid;
+
 err:
 	release_sock(sk);
 	return err;

@@ -3167,7 +3168,7 @@ static inline u32 netlink_hash(const voi
 	const struct netlink_sock *nlk = data;
 	struct netlink_compare_arg arg;
 
-	netlink_compare_arg_init(&arg, sock_net(&nlk->sk), nlk->portid);
+	netlink_compare_arg_init(&arg, sock_net(&nlk->sk), nlk->rhash_portid);
 	return jhash2((u32 *)&arg, netlink_compare_arg_len / sizeof(u32), seed);
 }
net/netlink/af_netlink.h +1 -0
@@ -25,6 +25,7 @@ struct netlink_ring {
 struct netlink_sock {
 	/* struct sock has to be the first member of netlink_sock */
 	struct sock		sk;
+	u32			rhash_portid;
 	u32			portid;
 	u32			dst_portid;
 	u32			dst_group;

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/netlink-replace-rhash_portid-with-bound.patch queue-4.1/netlink-fix-autobind-race-condition-that-leads-to-zero-port-id.patch