5e5dc33d5d
The following panic is observed when bringing up (veth_open) a veth device that has an XDP program attached. [ 61.519185] kernel BUG at net/core/dev.c:6442! [ 61.519456] invalid opcode: 0000 [#1] PREEMPT SMP PTI [ 61.519752] CPU: 0 PID: 408 Comm: ip Tainted: G W 6.1.0-rc2-185930-gd9095f92950b-dirty #26 [ 61.520288] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 [ 61.520806] RIP: 0010:napi_enable+0x3d/0x40 [ 61.521077] Code: f6 f6 80 61 08 00 00 02 74 0d 48 83 bf 88 01 00 00 00 74 03 80 cd 01 48 89 d0 f0 48 0f b1 4f 10 48 39 c2 75 c8 c3 cc cc cc cc <0f> 0b 90 48 8b 87 b0 00 00 00 48 81 c7 b0 00 00 00 45 31 c0 48 39 [ 61.522226] RSP: 0018:ffffbc9800cc36f8 EFLAGS: 00010246 [ 61.522557] RAX: 0000000000000001 RBX: 0000000000000300 RCX: 0000000000000001 [ 61.523004] RDX: 0000000000000010 RSI: ffffffff8b0de852 RDI: ffff9f03848e5000 [ 61.523452] RBP: 0000000000000000 R08: 0000000000000800 R09: 0000000000000000 [ 61.523899] R10: ffff9f0384a96800 R11: ffffffffffa48061 R12: ffff9f03849c3000 [ 61.524345] R13: 0000000000000300 R14: ffff9f03848e5000 R15: 0000001000000100 [ 61.524792] FS: 00007f58cb64d2c0(0000) GS:ffff9f03bbc00000(0000) knlGS:0000000000000000 [ 61.525301] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 61.525673] CR2: 00007f6cc629b498 CR3: 000000010498c000 CR4: 00000000000006f0 [ 61.526121] Call Trace: [ 61.526284] <TASK> [ 61.526425] __veth_napi_enable_range+0xd6/0x230 [ 61.526723] veth_enable_xdp+0xd0/0x160 [ 61.526969] veth_open+0x2e/0xc0 [ 61.527180] __dev_open+0xe2/0x1b0 [ 61.527405] __dev_change_flags+0x1a1/0x210 [ 61.527673] dev_change_flags+0x1c/0x60 This happens because we are calling veth_napi_enable() on already enabled queues. The root cause is in commit 2e0de6366ac16 changed the control logic dropping this case, if (priv->_xdp_prog) { err = veth_enable_xdp(dev); if (err) return err; - } else if (veth_gro_requested(dev)) { + /* refer to the logic in veth_xdp_set() */ + if (!rtnl_dereference(peer_rq->napi)) { + err = veth_napi_enable(peer); + if (err) + return err; + } so that now veth_napi_enable is called if the peer has not yet initialiazed its peer_rq->napi. The issue is this will happen even if the NIC is not up. Then in veth_enable_xdp just above we have similar path, veth_enable_xdp napi_already_on = (dev->flags & IFF_UP) && rcu_access_pointer(rq->napi) err = veth_enable_xdp_range(dev, 0, dev->real_num_rx_queues, napi_already_on); The trouble is an xdp prog is assigned before bringing the device up each of the veth_open path will enable the peers xdp napi structs. But then when we bring the peer up it will similar try to enable again because from veth_open the IFF_UP flag is not set until after the op in __dev_open so we believe napi_alread_on = false. To fix this just drop the IFF_UP test and rely on checking if the napi struct is enabled. This also matches the peer check in veth_xdp for disabling. To reproduce run ./test_xdp_meta.sh I found adding Cilium/Tetragon tests for XDP. Fixes: 2e0de6366ac16 ("veth: Avoid drop packets when xdp_redirect performs") Signed-off-by: John Fastabend <john.fastabend@gmail.com> Link: https://lore.kernel.org/r/20221108221650.808950-2-john.fastabend@gmail.com Acked-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.