| From 596c949fc4a36913b1d8046a4b299afaed0e24bc Mon Sep 17 00:00:00 2001 |
| From: "danborkmann@iogearbox.net" <danborkmann@iogearbox.net> |
| Date: Fri, 10 Aug 2012 22:48:54 +0000 |
| Subject: [PATCH] af_packet: remove BUG statement in tpacket_destruct_skb |
| |
| commit 7f5c3e3a80e6654cf48dfba7cf94f88c6b505467 upstream. |
| |
| Here's a quote of the comment about the BUG macro from asm-generic/bug.h: |
| |
| Don't use BUG() or BUG_ON() unless there's really no way out; one |
| example might be detecting data structure corruption in the middle |
| of an operation that can't be backed out of. If the (sub)system |
| can somehow continue operating, perhaps with reduced functionality, |
| it's probably not BUG-worthy. |
| |
| If you're tempted to BUG(), think again: is completely giving up |
| really the *only* solution? There are usually better options, where |
| users don't need to reboot ASAP and can mostly shut down cleanly. |
| |
| In our case, the status flag of a ring buffer slot is managed from both sides, |
| the kernel space and the user space. This means that even though the kernel |
| side might work as expected, the user space screws up and changes this flag |
| right between the send(2) is triggered when the flag is changed to |
| TP_STATUS_SENDING and a given skb is destructed after some time. Then, this |
| will hit the BUG macro. As David suggested, the best solution is to simply |
| remove this statement since it cannot be used for kernel side internal |
| consistency checks. I've tested it and the system still behaves /stable/ in |
| this case, so in accordance with the above comment, we should rather remove it. |
| |
| Signed-off-by: Daniel Borkmann <daniel.borkmann@tik.ee.ethz.ch> |
| Signed-off-by: David S. Miller <davem@davemloft.net> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| --- |
| net/packet/af_packet.c | 1 - |
| 1 file changed, 1 deletion(-) |
| |
| diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c |
| index 4096a66f6379..dbe4dd160631 100644 |
| --- a/net/packet/af_packet.c |
| +++ b/net/packet/af_packet.c |
| @@ -812,7 +812,6 @@ static void tpacket_destruct_skb(struct sk_buff *skb) |
| |
| if (likely(po->tx_ring.pg_vec)) { |
| ph = skb_shinfo(skb)->destructor_arg; |
| - BUG_ON(__packet_get_status(po, ph) != TP_STATUS_SENDING); |
| BUG_ON(atomic_read(&po->tx_ring.pending) == 0); |
| atomic_dec(&po->tx_ring.pending); |
| __packet_set_status(po, ph, TP_STATUS_AVAILABLE); |
| -- |
| 1.8.5.2 |
| |
