On 2019-11-26 08:13:35 [+0100], Joerg Vehlow wrote:
> From: Joerg Vehlow <joerg.vehlow@xxxxxxxxxxx>
>
> During the skb_queue_splice_init the tasklet could have been preempted
> and_skb_queue_tail called, which led to an inconsistent queue.
>
> Affected are all rt kernels up to 5.0.19-rt11 (due to bh rework).
>
> It was found using ipsec stress tests (e.g. ipcomp) in ltp suite.
> Running them in a continous loop triggered the bug in qemu within 5-10 retries.
Acked-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> [ 139.717259] BUG: unable to handle kernel NULL pointer dereference at 0000000000000518
> [ 139.717260] PGD 0 P4D 0
> [ 139.717262] Oops: 0000 [#1] PREEMPT SMP PTI
> [ 139.717273] CPU: 2 PID: 11987 Comm: netstress Not tainted 4.19.59-rt24-preemt-rt #1
> [ 139.717274] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-0-ga698c8995f-prebuilt.qemu.org 04/01/2014
> [ 139.717306] RIP: 0010:xfrm_trans_reinject+0x97/0xd0
> [ 139.717307] Code: 42 eb 45 83 6d b0 01 31 f6 48 8b 42 08 48 c7 42 08 00 00 00 00 48 8b 0a 48 c7 02 00 00 00 00 48 89 41 08 48 89 08 48 8b 42 10 <48> 8b b8 18 05 00 00 48 8b 42 40 e8 d9 e1 4b 00 48 8b 55 a0 48 39
> [ 139.717307] RSP: 0018:ffffc900007b37e8 EFLAGS: 00010246
> [ 139.717308] RAX: 0000000000000000 RBX: ffffc900007b37e8 RCX: ffff88807db206a8
> [ 139.717309] RDX: ffff88807db206a8 RSI: 0000000000000000 RDI: 0000000000000000
> [ 139.717309] RBP: ffffc900007b3848 R08: 0000000000000001 R09: ffffc900007b35c8
> [ 139.717309] R10: ffffea0001dcfc00 R11: 00000000000890c4 R12: ffff88807db20680
> [ 139.717310] R13: 00000000000f4240 R14: 0000000000000000 R15: 0000000000000000
> [ 139.717310] FS: 00007f4643034700(0000) GS:ffff88807db00000(0000) knlGS:0000000000000000
> [ 139.717311] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 139.717337] CR2: 0000000000000518 CR3: 00000000769c6000 CR4: 00000000000006e0
> [ 139.717350] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 139.717350] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [ 139.717350] Call Trace:
> [ 139.717387] tasklet_action_common.isra.18+0x6d/0xd0
> [ 139.717388] tasklet_action+0x1d/0x20
> [ 139.717389] do_current_softirqs+0x196/0x360
> [ 139.717390] __local_bh_enable+0x51/0x60
> [ 139.717397] ip_finish_output2+0x18b/0x3f0
> [ 139.717408] ? task_rq_lock+0x53/0xe0
> [ 139.717415] ip_finish_output+0xbe/0x1b0
> [ 139.717416] ip_output+0x72/0x100
> [ 139.717422] ? ipcomp_output+0x5e/0x280
> [ 139.717424] xfrm_output_resume+0x4b5/0x540
> [ 139.717436] ? refcount_dec_and_test_checked+0x11/0x20
> [ 139.717443] ? kfree_skbmem+0x33/0x80
> [ 139.717444] xfrm_output+0xd7/0x110
> [ 139.717451] xfrm4_output_finish+0x2b/0x30
> [ 139.717452] __xfrm4_output+0x3a/0x50
> [ 139.717453] xfrm4_output+0x40/0xe0
> [ 139.717454] ? xfrm_dst_check+0x174/0x250
> [ 139.717455] ? xfrm4_output+0x40/0xe0
> [ 139.717456] ? xfrm_dst_check+0x174/0x250
> [ 139.717457] ip_local_out+0x3b/0x50
> [ 139.717458] __ip_queue_xmit+0x16b/0x420
> [ 139.717464] ip_queue_xmit+0x10/0x20
> [ 139.717466] __tcp_transmit_skb+0x566/0xad0
> [ 139.717467] tcp_write_xmit+0x3a4/0x1050
> [ 139.717468] __tcp_push_pending_frames+0x35/0xe0
> [ 139.717469] tcp_push+0xdb/0x100
> [ 139.717469] tcp_sendmsg_locked+0x491/0xd70
> [ 139.717470] tcp_sendmsg+0x2c/0x50
> [ 139.717476] inet_sendmsg+0x3e/0xf0
> [ 139.717483] sock_sendmsg+0x3e/0x50
> [ 139.717484] __sys_sendto+0x114/0x1a0
> [ 139.717491] ? __rt_mutex_unlock+0xe/0x10
> [ 139.717492] ? _mutex_unlock+0xe/0x10
> [ 139.717500] ? ksys_write+0xc5/0xe0
> [ 139.717501] __x64_sys_sendto+0x28/0x30
> [ 139.717503] do_syscall_64+0x4d/0x110
> [ 139.717504] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
> Signed-off-by: Joerg Vehlow <joerg.vehlow@xxxxxxxxxxx>
> ---
> net/xfrm/xfrm_input.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/net/xfrm/xfrm_input.c b/net/xfrm/xfrm_input.c
> index 790b514f86b6..4c4e669fcd16 100644
> --- a/net/xfrm/xfrm_input.c
> +++ b/net/xfrm/xfrm_input.c
> @@ -512,12 +512,15 @@ EXPORT_SYMBOL(xfrm_input_resume);
>
> static void xfrm_trans_reinject(unsigned long data)
> {
> + unsigned long flags;
> struct xfrm_trans_tasklet *trans = (void *)data;
> struct sk_buff_head queue;
> struct sk_buff *skb;
>
> __skb_queue_head_init(&queue);
> + spin_lock_irqsave(&trans->queue.lock, flags);
> skb_queue_splice_init(&trans->queue, &queue);
> + spin_unlock_irqrestore(&trans->queue.lock, flags);
>
> while ((skb = __skb_dequeue(&queue)))
> XFRM_TRANS_SKB_CB(skb)->finish(dev_net(skb->dev), NULL, skb);
> @@ -535,7 +538,7 @@ int xfrm_trans_queue(struct sk_buff *skb,
> return -ENOBUFS;
>
> XFRM_TRANS_SKB_CB(skb)->finish = finish;
> - __skb_queue_tail(&trans->queue, skb);
> + skb_queue_tail(&trans->queue, skb);
> tasklet_schedule(&trans->tasklet);
> return 0;
> }
> @@ -560,7 +563,7 @@ void __init xfrm_input_init(void)
> struct xfrm_trans_tasklet *trans;
>
> trans = &per_cpu(xfrm_trans_tasklet, i);
> - __skb_queue_head_init(&trans->queue);
> + skb_queue_head_init(&trans->queue);
> tasklet_init(&trans->tasklet, xfrm_trans_reinject,
> (unsigned long)trans);
> }
> --
> 2.20.1
>
Sebastian
