From: Sean Tranchetti stranche@codeaurora.org
[ Upstream commit fc2d5cfdcfe2ab76b263d91429caa22451123085 ]
Attempting to avoid cloning the skb when broadcasting by inflating the refcount with sock_hold/sock_put while under RCU lock is dangerous and violates RCU principles. It leads to subtle race conditions when attempting to free the SKB, as we may reference sockets that have already been freed by the stack.
Unable to handle kernel paging request at virtual address 6b6b6b6b6b6c4b [006b6b6b6b6b6c4b] address between user and kernel address ranges Internal error: Oops: 96000004 [#1] PREEMPT SMP task: fffffff78f65b380 task.stack: ffffff8049a88000 pc : sock_rfree+0x38/0x6c lr : skb_release_head_state+0x6c/0xcc Process repro (pid: 7117, stack limit = 0xffffff8049a88000) Call trace: sock_rfree+0x38/0x6c skb_release_head_state+0x6c/0xcc skb_release_all+0x1c/0x38 __kfree_skb+0x1c/0x30 kfree_skb+0xd0/0xf4 pfkey_broadcast+0x14c/0x18c pfkey_sendmsg+0x1d8/0x408 sock_sendmsg+0x44/0x60 ___sys_sendmsg+0x1d0/0x2a8 __sys_sendmsg+0x64/0xb4 SyS_sendmsg+0x34/0x4c el0_svc_naked+0x34/0x38 Kernel panic - not syncing: Fatal exception
Suggested-by: Eric Dumazet eric.dumazet@gmail.com Signed-off-by: Sean Tranchetti stranche@codeaurora.org Signed-off-by: Steffen Klassert steffen.klassert@secunet.com Signed-off-by: Sasha Levin sashal@kernel.org --- net/key/af_key.c | 40 +++++++++++++++------------------------- 1 file changed, 15 insertions(+), 25 deletions(-)
diff --git a/net/key/af_key.c b/net/key/af_key.c index 9d61266526e7..7da629d59717 100644 --- a/net/key/af_key.c +++ b/net/key/af_key.c @@ -196,30 +196,22 @@ static int pfkey_release(struct socket *sock) return 0; }
-static int pfkey_broadcast_one(struct sk_buff *skb, struct sk_buff **skb2, - gfp_t allocation, struct sock *sk) +static int pfkey_broadcast_one(struct sk_buff *skb, gfp_t allocation, + struct sock *sk) { int err = -ENOBUFS;
- sock_hold(sk); - if (*skb2 == NULL) { - if (refcount_read(&skb->users) != 1) { - *skb2 = skb_clone(skb, allocation); - } else { - *skb2 = skb; - refcount_inc(&skb->users); - } - } - if (*skb2 != NULL) { - if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) { - skb_set_owner_r(*skb2, sk); - skb_queue_tail(&sk->sk_receive_queue, *skb2); - sk->sk_data_ready(sk); - *skb2 = NULL; - err = 0; - } + if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) + return err; + + skb = skb_clone(skb, allocation); + + if (skb) { + skb_set_owner_r(skb, sk); + skb_queue_tail(&sk->sk_receive_queue, skb); + sk->sk_data_ready(sk); + err = 0; } - sock_put(sk); return err; }
@@ -234,7 +226,6 @@ static int pfkey_broadcast(struct sk_buff *skb, gfp_t allocation, { struct netns_pfkey *net_pfkey = net_generic(net, pfkey_net_id); struct sock *sk; - struct sk_buff *skb2 = NULL; int err = -ESRCH;
/* XXX Do we need something like netlink_overrun? I think @@ -253,7 +244,7 @@ static int pfkey_broadcast(struct sk_buff *skb, gfp_t allocation, * socket. */ if (pfk->promisc) - pfkey_broadcast_one(skb, &skb2, GFP_ATOMIC, sk); + pfkey_broadcast_one(skb, GFP_ATOMIC, sk);
/* the exact target will be processed later */ if (sk == one_sk) @@ -268,7 +259,7 @@ static int pfkey_broadcast(struct sk_buff *skb, gfp_t allocation, continue; }
- err2 = pfkey_broadcast_one(skb, &skb2, GFP_ATOMIC, sk); + err2 = pfkey_broadcast_one(skb, GFP_ATOMIC, sk);
/* Error is cleared after successful sending to at least one * registered KM */ @@ -278,9 +269,8 @@ static int pfkey_broadcast(struct sk_buff *skb, gfp_t allocation, rcu_read_unlock();
if (one_sk != NULL) - err = pfkey_broadcast_one(skb, &skb2, allocation, one_sk); + err = pfkey_broadcast_one(skb, allocation, one_sk);
- kfree_skb(skb2); kfree_skb(skb); return err; }