This is a note to let you know that I've just added the patch titled
bpf: sockmap missing NULL psock check
to the 4.14-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:
bpf-sockmap-missing-null-psock-check.patch
and it can be found in the queue-4.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Wed Feb 28 16:23:28 CET 2018
From: John Fastabend <john.fastabend@xxxxxxxxx>
Date: Thu, 4 Jan 2018 20:02:09 -0800
Subject: bpf: sockmap missing NULL psock check
From: John Fastabend <john.fastabend@xxxxxxxxx>
[ Upstream commit 5731a879d03bdaa00265f8ebc32dfd0e65d25276 ]
Add psock NULL check to handle a racing sock event that can get the
sk_callback_lock before this case but after xchg happens causing the
refcnt to hit zero and sock user data (psock) to be null and queued
for garbage collection.
Also add a comment in the code because this is a bit subtle and
not obvious in my opinion.
Signed-off-by: John Fastabend <john.fastabend@xxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/bpf/sockmap.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -588,8 +588,15 @@ static void sock_map_free(struct bpf_map
write_lock_bh(&sock->sk_callback_lock);
psock = smap_psock_sk(sock);
- smap_list_remove(psock, &stab->sock_map[i]);
- smap_release_sock(psock, sock);
+ /* This check handles a racing sock event that can get the
+ * sk_callback_lock before this case but after xchg happens
+ * causing the refcnt to hit zero and sock user data (psock)
+ * to be null and queued for garbage collection.
+ */
+ if (likely(psock)) {
+ smap_list_remove(psock, &stab->sock_map[i]);
+ smap_release_sock(psock, sock);
+ }
write_unlock_bh(&sock->sk_callback_lock);
}
rcu_read_unlock();
Patches currently in stable-queue which might be from john.fastabend@xxxxxxxxx are
queue-4.14/bpf-sockmap-missing-null-psock-check.patch