From: Nikolay Aleksandrov nikolay@cumulusnetworks.com
[ Upstream commit 7eb9d7675c08937cd11d32b0b40442d4d731c5ee ]
We need to calculate the skb size correctly otherwise we risk triggering skb_over_panic[1]. The issue is that data_len is added to the skb in a nl attribute, but we don't account for its header size (nlattr 4 bytes) and alignment. We account for it when calculating the total size in the > PSAMPLE_MAX_PACKET_SIZE comparison correctly, but not when allocating after that. The fix is simple - use nla_total_size() for data_len when allocating.
To reproduce: $ tc qdisc add dev eth1 clsact $ tc filter add dev eth1 egress matchall action sample rate 1 group 1 trunc 129 $ mausezahn eth1 -b bcast -a rand -c 1 -p 129 < skb_over_panic BUG(), tail is 4 bytes past skb->end >
[1] Trace: [ 50.459526][ T3480] skbuff: skb_over_panic: text:(____ptrval____) len:196 put:136 head:(____ptrval____) data:(____ptrval____) tail:0xc4 end:0xc0 dev:<NULL> [ 50.474339][ T3480] ------------[ cut here ]------------ [ 50.481132][ T3480] kernel BUG at net/core/skbuff.c:108! [ 50.486059][ T3480] invalid opcode: 0000 [#1] PREEMPT SMP [ 50.489463][ T3480] CPU: 3 PID: 3480 Comm: mausezahn Not tainted 5.4.0-rc7 #108 [ 50.492844][ T3480] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-2.fc30 04/01/2014 [ 50.496551][ T3480] RIP: 0010:skb_panic+0x79/0x7b [ 50.498261][ T3480] Code: bc 00 00 00 41 57 4c 89 e6 48 c7 c7 90 29 9a 83 4c 8b 8b c0 00 00 00 50 8b 83 b8 00 00 00 50 ff b3 c8 00 00 00 e8 ae ef c0 fe <0f> 0b e8 2f df c8 fe 48 8b 55 08 44 89 f6 4c 89 e7 48 c7 c1 a0 22 [ 50.504111][ T3480] RSP: 0018:ffffc90000447a10 EFLAGS: 00010282 [ 50.505835][ T3480] RAX: 0000000000000087 RBX: ffff888039317d00 RCX: 0000000000000000 [ 50.507900][ T3480] RDX: 0000000000000000 RSI: ffffffff812716e1 RDI: 00000000ffffffff [ 50.509820][ T3480] RBP: ffffc90000447a60 R08: 0000000000000001 R09: 0000000000000000 [ 50.511735][ T3480] R10: ffffffff81d4f940 R11: 0000000000000000 R12: ffffffff834a22b0 [ 50.513494][ T3480] R13: ffffffff82c10433 R14: 0000000000000088 R15: ffffffff838a8084 [ 50.515222][ T3480] FS: 00007f3536462700(0000) GS:ffff88803eac0000(0000) knlGS:0000000000000000 [ 50.517135][ T3480] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 50.518583][ T3480] CR2: 0000000000442008 CR3: 000000003b222000 CR4: 00000000000006e0 [ 50.520723][ T3480] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 50.522709][ T3480] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 50.524450][ T3480] Call Trace: [ 50.525214][ T3480] skb_put.cold+0x1b/0x1b [ 50.526171][ T3480] psample_sample_packet+0x1d3/0x340 [ 50.527307][ T3480] tcf_sample_act+0x178/0x250 [ 50.528339][ T3480] tcf_action_exec+0xb1/0x190 [ 50.529354][ T3480] mall_classify+0x67/0x90 [ 50.530332][ T3480] tcf_classify+0x72/0x160 [ 50.531286][ T3480] __dev_queue_xmit+0x3db/0xd50 [ 50.532327][ T3480] dev_queue_xmit+0x18/0x20 [ 50.533299][ T3480] packet_sendmsg+0xee7/0x2090 [ 50.534331][ T3480] sock_sendmsg+0x54/0x70 [ 50.535271][ T3480] __sys_sendto+0x148/0x1f0 [ 50.536252][ T3480] ? tomoyo_file_ioctl+0x23/0x30 [ 50.537334][ T3480] ? ksys_ioctl+0x5e/0xb0 [ 50.540068][ T3480] __x64_sys_sendto+0x2a/0x30 [ 50.542810][ T3480] do_syscall_64+0x73/0x1f0 [ 50.545383][ T3480] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 50.548477][ T3480] RIP: 0033:0x7f35357d6fb3 [ 50.551020][ T3480] Code: 48 8b 0d 18 90 20 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d f9 d3 20 00 00 75 13 49 89 ca b8 2c 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 34 c3 48 83 ec 08 e8 eb f6 ff ff 48 89 04 24 [ 50.558547][ T3480] RSP: 002b:00007ffe0c7212c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002c [ 50.561870][ T3480] RAX: ffffffffffffffda RBX: 0000000001dac010 RCX: 00007f35357d6fb3 [ 50.565142][ T3480] RDX: 0000000000000082 RSI: 0000000001dac2a2 RDI: 0000000000000003 [ 50.568469][ T3480] RBP: 00007ffe0c7212f0 R08: 00007ffe0c7212d0 R09: 0000000000000014 [ 50.571731][ T3480] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000082 [ 50.574961][ T3480] R13: 0000000001dac2a2 R14: 0000000000000001 R15: 0000000000000003 [ 50.578170][ T3480] Modules linked in: sch_ingress virtio_net [ 50.580976][ T3480] ---[ end trace 61a515626a595af6 ]---
CC: Yotam Gigi yotamg@mellanox.com CC: Jiri Pirko jiri@mellanox.com CC: Jamal Hadi Salim jhs@mojatatu.com CC: Simon Horman simon.horman@netronome.com CC: Roopa Prabhu roopa@cumulusnetworks.com Fixes: 6ae0a6286171 ("net: Introduce psample, a new genetlink channel for packet sampling") Signed-off-by: Nikolay Aleksandrov nikolay@cumulusnetworks.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/psample/psample.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/net/psample/psample.c +++ b/net/psample/psample.c @@ -223,7 +223,7 @@ void psample_sample_packet(struct psampl data_len = PSAMPLE_MAX_PACKET_SIZE - meta_len - NLA_HDRLEN - NLA_ALIGNTO;
- nl_skb = genlmsg_new(meta_len + data_len, GFP_ATOMIC); + nl_skb = genlmsg_new(meta_len + nla_total_size(data_len), GFP_ATOMIC); if (unlikely(!nl_skb)) return;