[PATCH net 0/2] wireguard patches for 5.18-rc4

[PATCH net 0/2] wireguard patches for 5.18-rc4

[Jason A. Donenfeld]

Hi Davekub,

Here are two small wireguard fixes for 5.18-rc4:

1) We enable ACPI in the QEMU test harness, so that multiple CPUs are
   actually used on x86 for testing for races.

2) Sending skbs with metadata dsts attached resulted in a null pointer
   dereference, triggerable from executing eBPF programs. The fix is a
   oneliner, changing a skb_dst() null check into a skb_valid_dst()
   boolean check.

Thanks,
Jason


Jason A. Donenfeld (1):
  wireguard: selftests: enable ACPI for SMP

Nikolay Aleksandrov (1):
  wireguard: device: check for metadata_dst with skb_valid_dst()

 drivers/net/wireguard/device.c                            | 3 ++-
 tools/testing/selftests/wireguard/qemu/arch/i686.config   | 1 +
 tools/testing/selftests/wireguard/qemu/arch/x86_64.config | 1 +
 3 files changed, 4 insertions(+), 1 deletion(-)

-- 
2.35.1

[PATCH net 1/2] wireguard: selftests: enable ACPI for SMP

[Jason A. Donenfeld]

It turns out that by having CONFIG_ACPI=n, we've been failing to boot
additional CPUs, and so these systems were functionally UP. The code
bloat is unfortunate for build times, but I don't see an alternative. So
this commit sets CONFIG_ACPI=y for x86_64 and i686 configs.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 tools/testing/selftests/wireguard/qemu/arch/i686.config   | 1 +
 tools/testing/selftests/wireguard/qemu/arch/x86_64.config | 1 +
 2 files changed, 2 insertions(+)

diff --git a/tools/testing/selftests/wireguard/qemu/arch/i686.config b/tools/testing/selftests/wireguard/qemu/arch/i686.config
index a85025d7206e..a9b4fe795048 100644
--- a/tools/testing/selftests/wireguard/qemu/arch/i686.config
+++ b/tools/testing/selftests/wireguard/qemu/arch/i686.config
@@ -1,3 +1,4 @@
+CONFIG_ACPI=y
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_CMDLINE_BOOL=y
diff --git a/tools/testing/selftests/wireguard/qemu/arch/x86_64.config b/tools/testing/selftests/wireguard/qemu/arch/x86_64.config
index 00a1ef4869d5..45dd53a0d760 100644
--- a/tools/testing/selftests/wireguard/qemu/arch/x86_64.config
+++ b/tools/testing/selftests/wireguard/qemu/arch/x86_64.config
@@ -1,3 +1,4 @@
+CONFIG_ACPI=y
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_CMDLINE_BOOL=y
-- 
2.35.1

[PATCH net 2/2] wireguard: device: check for metadata_dst with skb_valid_dst()

[Jason A. Donenfeld]

From: Nikolay Aleksandrov <razor@blackwall.org>

When we try to transmit an skb with md_dst attached through wireguard
we hit a null pointer dereference in wg_xmit() due to the use of
dst_mtu() which calls into dst_blackhole_mtu() which in turn tries to
dereference dst->dev.

Since wireguard doesn't use md_dsts we should use skb_valid_dst(), which
checks for DST_METADATA flag, and if it's set, then falls back to
wireguard's device mtu. That gives us the best chance of transmitting
the packet; otherwise if the blackhole netdev is used we'd get
ETH_MIN_MTU.

 [  263.693506] BUG: kernel NULL pointer dereference, address: 00000000000000e0
 [  263.693908] #PF: supervisor read access in kernel mode
 [  263.694174] #PF: error_code(0x0000) - not-present page
 [  263.694424] PGD 0 P4D 0
 [  263.694653] Oops: 0000 [#1] PREEMPT SMP NOPTI
 [  263.694876] CPU: 5 PID: 951 Comm: mausezahn Kdump: loaded Not tainted 5.18.0-rc1+ #522
 [  263.695190] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1.fc35 04/01/2014
 [  263.695529] RIP: 0010:dst_blackhole_mtu+0x17/0x20
 [  263.695770] Code: 00 00 00 0f 1f 44 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 8b 47 10 48 83 e0 fc 8b 40 04 85 c0 75 09 48 8b 07 <8b> 80 e0 00 00 00 c3 66 90 0f 1f 44 00 00 48 89 d7 be 01 00 00 00
 [  263.696339] RSP: 0018:ffffa4a4422fbb28 EFLAGS: 00010246
 [  263.696600] RAX: 0000000000000000 RBX: ffff8ac9c3553000 RCX: 0000000000000000
 [  263.696891] RDX: 0000000000000401 RSI: 00000000fffffe01 RDI: ffffc4a43fb48900
 [  263.697178] RBP: ffffa4a4422fbb90 R08: ffffffff9622635e R09: 0000000000000002
 [  263.697469] R10: ffffffff9b69a6c0 R11: ffffa4a4422fbd0c R12: ffff8ac9d18b1a00
 [  263.697766] R13: ffff8ac9d0ce1840 R14: ffff8ac9d18b1a00 R15: ffff8ac9c3553000
 [  263.698054] FS:  00007f3704c337c0(0000) GS:ffff8acaebf40000(0000) knlGS:0000000000000000
 [  263.698470] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 [  263.698826] CR2: 00000000000000e0 CR3: 0000000117a5c000 CR4: 00000000000006e0
 [  263.699214] Call Trace:
 [  263.699505]  <TASK>
 [  263.699759]  wg_xmit+0x411/0x450
 [  263.700059]  ? bpf_skb_set_tunnel_key+0x46/0x2d0
 [   263.700382]  ? dev_queue_xmit_nit+0x31/0x2b0
 [  263.700719]  dev_hard_start_xmit+0xd9/0x220
 [  263.701047]  __dev_queue_xmit+0x8b9/0xd30
 [  263.701344]  __bpf_redirect+0x1a4/0x380
 [  263.701664]  __dev_queue_xmit+0x83b/0xd30
 [  263.701961]  ? packet_parse_headers+0xb4/0xf0
 [  263.702275]  packet_sendmsg+0x9a8/0x16a0
 [  263.702596]  ? _raw_spin_unlock_irqrestore+0x23/0x40
 [  263.702933]  sock_sendmsg+0x5e/0x60
 [  263.703239]  __sys_sendto+0xf0/0x160
 [  263.703549]  __x64_sys_sendto+0x20/0x30
 [  263.703853]  do_syscall_64+0x3b/0x90
 [  263.704162]  entry_SYSCALL_64_after_hwframe+0x44/0xae
 [  263.704494] RIP: 0033:0x7f3704d50506
 [  263.704789] Code: 48 c7 c0 ff ff ff ff eb b7 66 2e 0f 1f 84 00 00 00 00 00 90 41 89 ca 64 8b 04 25 18 00 00 00 85 c0 75 11 b8 2c 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 72 c3 90 55 48 83 ec 30 44 89 4c 24 2c 4c 89
 [  263.705652] RSP: 002b:00007ffe954b0b88 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
 [  263.706141] RAX: ffffffffffffffda RBX: 0000558bb259b490 RCX: 00007f3704d50506
 [  263.706544] RDX: 000000000000004a RSI: 0000558bb259b7b2 RDI: 0000000000000003
 [  263.706952] RBP: 0000000000000000 R08: 00007ffe954b0b90 R09: 0000000000000014
 [  263.707339] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe954b0b90
 [  263.707735] R13: 000000000000004a R14: 0000558bb259b7b2 R15: 0000000000000001
 [  263.708132]  </TASK>
 [  263.708398] Modules linked in: bridge netconsole bonding [last unloaded: bridge]
 [  263.708942] CR2: 00000000000000e0

Cc: stable@vger.kernel.org
Fixes: e7096c131e51 ("net: WireGuard secure network tunnel")
Link: https://github.com/cilium/cilium/issues/19428
Reported-by: Martynas Pumputis <m@lambda.lt>
Signed-off-by: Nikolay Aleksandrov <razor@blackwall.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
 drivers/net/wireguard/device.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/wireguard/device.c b/drivers/net/wireguard/device.c
index 0fad1331303c..aa9a7a5970fd 100644
--- a/drivers/net/wireguard/device.c
+++ b/drivers/net/wireguard/device.c
@@ -19,6 +19,7 @@
 #include <linux/if_arp.h>
 #include <linux/icmp.h>
 #include <linux/suspend.h>
+#include <net/dst_metadata.h>
 #include <net/icmp.h>
 #include <net/rtnetlink.h>
 #include <net/ip_tunnels.h>
@@ -167,7 +168,7 @@ static netdev_tx_t wg_xmit(struct sk_buff *skb, struct net_device *dev)
 		goto err_peer;
 	}
 
-	mtu = skb_dst(skb) ? dst_mtu(skb_dst(skb)) : dev->mtu;
+	mtu = skb_valid_dst(skb) ? dst_mtu(skb_dst(skb)) : dev->mtu;
 
 	__skb_queue_head_init(&packets);
 	if (!skb_is_gso(skb)) {
-- 
2.35.1

Re: [PATCH net 0/2] wireguard patches for 5.18-rc4

[Jakub Kicinski]

On Thu, 21 Apr 2022 15:48:03 +0200 Jason A. Donenfeld wrote:
> Hi Davekub,

YES :D

> Here are two small wireguard fixes for 5.18-rc4:

Missed the PR, sadly. Paolo was handling it and he's on EU time.