From: l00219569 <lisi...@huawei.com> If fanout_add is preempted after running po-> fanout = match and before running __fanout_link, it will cause BUG_ON when __unregister_prot_hook call __fanout_unlink
so, we need add mutex_lock(&fanout_mutex) to __unregister_prot_hook or add spin_lock(&po->bind_lock) before po-> fanout = match this is a patch for add po->bind_lock in fanout_add test on linux 4.1.12: ./trinity -c setsockopt -C 2 -X & BUG: failure at net/packet/af_packet.c:1414/__fanout_unlink()! Kernel panic - not syncing: BUG! CPU: 2 PID: 2271 Comm: trinity-c0 Tainted: G W O 4.1.12 #1 Hardware name: Hisilicon PhosphorHi1382 FPGA (DT) Call trace: [<ffffffc000209414>] dump_backtrace+0x0/0xf8 [<ffffffc00020952c>] show_stack+0x20/0x28 [<ffffffc000635574>] dump_stack+0xac/0xe4 [<ffffffc000633fb8>] panic+0xf8/0x268 [<ffffffc0005fa778>] __unregister_prot_hook+0xa0/0x144 [<ffffffc0005fba48>] packet_set_ring+0x280/0x5b4 [<ffffffc0005fc33c>] packet_setsockopt+0x320/0x950 [<ffffffc000554a04>] SyS_setsockopt+0xa4/0xd4 Signed-off-by: nixiaoming <nixiaom...@huawei.com> Tested-by: wudesheng <dede...@huawei.com> --- net/packet/af_packet.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 54a18a8..7a52a3b 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1446,12 +1446,16 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags) default: return -EINVAL; } - - if (!po->running) + spin_lock(&po->bind_lock); + if (!po->running) { + spin_unlock(&po->bind_lock); return -EINVAL; + } - if (po->fanout) + if (po->fanout) { + spin_unlock(&po->bind_lock); return -EALREADY; + } mutex_lock(&fanout_mutex); match = NULL; @@ -1501,6 +1505,7 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags) } out: mutex_unlock(&fanout_mutex); + spin_unlock(&po->bind_lock); return err; } -- 2.10.1