/*
 * xfrm4_output.c - Common IPsec encapsulation code for IPv4.
 * Copyright (c) 2004 Herbert Xu <herbert@gondor.apana.org.au>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/if_ether.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/netfilter_ipv4.h>
#include <net/dst.h>
#include <net/ip.h>
#include <net/xfrm.h>
#include <net/icmp.h>

static int xfrm4_tunnel_check_size(struct sk_buff *skb)
{
	int mtu, ret = 0;

	if (IPCB(skb)->flags & IPSKB_XFRM_TUNNEL_SIZE)
		goto out;

	if (!(ip_hdr(skb)->frag_off & htons(IP_DF)) || skb->ignore_df)
		goto out;

	mtu = dst_mtu(skb_dst(skb));
	if (skb->len > mtu) {
		skb->protocol = htons(ETH_P_IP);

		if (skb->sk)
			xfrm_local_error(skb, mtu);
		else
			icmp_send(skb, ICMP_DEST_UNREACH,
				  ICMP_FRAG_NEEDED, htonl(mtu));
		ret = -EMSGSIZE;
	}
out:
	return ret;
}

int xfrm4_extract_output(struct xfrm_state *x, struct sk_buff *skb)
{
	int err;

	err = xfrm4_tunnel_check_size(skb);
	if (err)
		return err;

	XFRM_MODE_SKB_CB(skb)->protocol = ip_hdr(skb)->protocol;

	return xfrm4_extract_header(skb);
}

int xfrm4_prepare_output(struct xfrm_state *x, struct sk_buff *skb)
{
	int err;

	err = xfrm_inner_extract_output(x, skb);
	if (err)
		return err;

	IPCB(skb)->flags |= IPSKB_XFRM_TUNNEL_SIZE;
	skb->protocol = htons(ETH_P_IP);

	return x->outer_mode->output2(x, skb);
}
EXPORT_SYMBOL(xfrm4_prepare_output);

int xfrm4_output_finish(struct sock *sk, struct sk_buff *skb)
{
	memset(IPCB(skb), 0, sizeof(*IPCB(skb)));

#ifdef CONFIG_NETFILTER
	IPCB(skb)->flags |= IPSKB_XFRM_TRANSFORMED;
#endif

	return xfrm_output(sk, skb);
}

static int __xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
	struct xfrm_state *x = skb_dst(skb)->xfrm;

#ifdef CONFIG_NETFILTER
	if (!x) {
		IPCB(skb)->flags |= IPSKB_REROUTED;
		return dst_output(net, sk, skb);
	}
#endif

	return x->outer_mode->afinfo->output_finish(sk, skb);
}

int xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
	return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
			    net, sk, skb, NULL, skb_dst(skb)->dev,
			    __xfrm4_output,
			    !(IPCB(skb)->flags & IPSKB_REROUTED));
}

void xfrm4_local_error(struct sk_buff *skb, u32 mtu)
{
	struct iphdr *hdr;

	hdr = skb->encapsulation ? inner_ip_hdr(skb) : ip_hdr(skb);
	ip_local_error(skb->sk, EMSGSIZE, hdr->daddr,
		       inet_sk(skb->sk)->inet_dport, mtu);
}
/net-next.git/log/?id=926af6273fc683cd98cd0ce7bf0d04a02eed6742'>root</a>/<a href='/cgit.cgi/linux/net-next.git/log/net?id=926af6273fc683cd98cd0ce7bf0d04a02eed6742'>net</a>/<a href='/cgit.cgi/linux/net-next.git/log/net/ipv6?id=926af6273fc683cd98cd0ce7bf0d04a02eed6742'>ipv6</a>/<a href='/cgit.cgi/linux/net-next.git/log/net/ipv6/ip6_tunnel.c?id=926af6273fc683cd98cd0ce7bf0d04a02eed6742'>ip6_tunnel.c</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/cgit.cgi/linux/net-next.git/log/net/ipv6/ip6_tunnel.c?id=926af6273fc683cd98cd0ce7bf0d04a02eed6742&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th><th class='left'>Files</th><th class='left'>Lines</th></tr>
<tr><td><span title='2017-02-01 12:27:33 -0500'>2017-02-01</span></td><td><a href='/cgit.cgi/linux/net-next.git/commit/net/ipv6/ip6_tunnel.c?id=63117f09c768be05a0bf465911297dc76394f686'>ipv6: pointer math error in ip6_tnl_parse_tlv_enc_lim()</a></td><td>Dan Carpenter</td><td>1</td><td><span class='deletions'>-1</span>/<span class='insertions'>+1</span></td></tr>
><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2017-01-29 13:50:06 -0800</td></tr>
<tr><th>committer</th><td>Linus Torvalds &lt;torvalds@linux-foundation.org&gt;</td><td class='right'>2017-01-29 13:50:06 -0800</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/net/netlink?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>39cb2c9a316e77f6dfba96c543e55b6672d5a37e</a> (<a href='/cgit.cgi/linux/net-next.git/patch/net/netlink?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>98fe974ee4e20121253de7f61fc8d01bdb3821c1</a> /<a href='/cgit.cgi/linux/net-next.git/tree/net/netlink?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>net/netlink</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/net/netlink?id=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>2c5d9555d6d937966d79d4c6529a5f7b9206e405</a> (<a href='/cgit.cgi/linux/net-next.git/diff/net/netlink?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e&amp;id2=2c5d9555d6d937966d79d4c6529a5f7b9206e405'>diff</a>)</td></tr></table>
<div class='commit-subject'>drm/i915: Check for NULL i915_vma in intel_unpin_fb_obj()</div><div class='commit-msg'>I've seen this trigger twice now, where the i915_gem_object_to_ggtt()
call in intel_unpin_fb_obj() returns NULL, resulting in an oops
immediately afterwards as the (inlined) call to i915_vma_unpin_fence()
tries to dereference it.

It seems to be some race condition where the object is going away at
shutdown time, since both times happened when shutting down the X
server.  The call chains were different:

 - VT ioctl(KDSETMODE, KD_TEXT):

    intel_cleanup_plane_fb+0x5b/0xa0 [i915]
    drm_atomic_helper_cleanup_planes+0x6f/0x90 [drm_kms_helper]
    intel_atomic_commit_tail+0x749/0xfe0 [i915]
    intel_atomic_commit+0x3cb/0x4f0 [i915]
    drm_atomic_commit+0x4b/0x50 [drm]
    restore_fbdev_mode+0x14c/0x2a0 [drm_kms_helper]
    drm_fb_helper_restore_fbdev_mode_unlocked+0x34/0x80 [drm_kms_helper]
    drm_fb_helper_set_par+0x2d/0x60 [drm_kms_helper]
    intel_fbdev_set_par+0x18/0x70 [i915]
    fb_set_var+0x236/0x460
    fbcon_blank+0x30f/0x350
    do_unblank_screen+0xd2/0x1a0
    vt_ioctl+0x507/0x12a0
    tty_ioctl+0x355/0xc30
    do_vfs_ioctl+0xa3/0x5e0
    SyS_ioctl+0x79/0x90
    entry_SYSCALL_64_fastpath+0x13/0x94

 - i915 unpin_work workqueue:

    intel_unpin_work_fn+0x58/0x140 [i915]
    process_one_work+0x1f1/0x480
    worker_thread+0x48/0x4d0
    kthread+0x101/0x140

and this patch purely papers over the issue by adding a NULL pointer
check and a WARN_ON_ONCE() to avoid the oops that would then generally
make the machine unresponsive.

Other callers of i915_gem_object_to_ggtt() seem to also check for the
returned pointer being NULL and warn about it, so this clearly has
happened before in other places.

[ Reported it originally to the i915 developers on Jan 8, applying the
  ugly workaround on my own now after triggering the problem for the
  second time with no feedback.

  This is likely to be the same bug reported as

     https://bugs.freedesktop.org/show_bug.cgi?id=98829
     https://bugs.freedesktop.org/show_bug.cgi?id=99134

  which has a patch for the underlying problem, but it hasn't gotten to
  me, so I'm applying the workaround. ]

Cc: Daniel Vetter &lt;daniel.vetter@intel.com&gt;
Cc: Jani Nikula &lt;jani.nikula@linux.intel.com&gt;
Cc: Ville Syrjälä &lt;ville.syrjala@linux.intel.com&gt;
Cc: Chris Wilson &lt;chris@chris-wilson.co.uk&gt;
Cc: Maarten Lankhorst &lt;maarten.lankhorst@linux.intel.com&gt;
Cc: Tvrtko Ursulin &lt;tvrtko.ursulin@intel.com&gt;
Cc: Imre Deak &lt;imre.deak@intel.com&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>Diffstat</a> (limited to 'net/netlink')</div><table summary='diffstat' class='diffstat'>