mld_newpack() doesn't allow to allocate high order page, just order-0 allocation is allowed. If headroom size is too large, a kernel panic could occur in skb_put().
Test commands: ip netns add A ip netns add B ip link add veth0 type veth peer name veth1 ip link set veth0 netns A ip link set veth1 netns B ip netns exec A ip link set lo up ip netns exec A ip link set veth0 up ip netns exec A ip link add ip6tnl100 type ip6tnl local 2001:db8:99::1 \ remote 2001:db8:99::2 ip netns exec A ip -6 a a 2001:db8:100::1/64 dev ip6tnl100 ip netns exec A ip link set ip6tnl100 up for i in {99..1} do let A=$i-1 ip netns exec A ip link add ip6tnl$i type ip6tnl local \ 2001:db8:$A::1 remote 2001:db8:$A::2 ip netns exec A ip -6 a a 2001:db8:$i::1/64 dev ip6tnl$i ip netns exec A ip link set ip6tnl$i up done ip netns exec A ip -6 a a 2001:db8:0::1/64 dev veth0 ip netns exec B ip link set lo up ip netns exec B ip link set veth1 up ip netns exec B ip link add ip6tnl100 type ip6tnl local 2001:db8:99::2 \ remote 2001:db8:99::1 ip netns exec B ip -6 a a 2001:db8:100::2/64 dev ip6tnl100 ip netns exec B ip link set ip6tnl100 up for i in {99..1} do let B=$i-1 ip netns exec B ip link add ip6tnl$i type ip6tnl local \ 2001:db8:$B::2 remote 2001:db8:$B::1 ip netns exec B ip -6 a a 2001:db8:$i::2/64 dev ip6tnl$i ip netns exec B ip link set ip6tnl$i up done ip netns exec B ip -6 a a 2001:db8:0::2/64 dev veth1 Splat looks like: [ 104.047694][ T104] skbuff: skb_over_panic: text:ffffffffb0c31a92 len:56 put:8 head:ffff888009609000 data:ffff888009609e90 tail:0xec8 end:0xec0 dev:ip6gre4b [ 104.053431][ T104] ------------[ cut here ]------------ [ 104.055733][ T104] kernel BUG at net/core/skbuff.c:109! [ 104.058014][ T104] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI [ 104.060761][ T104] CPU: 4 PID: 104 Comm: kworker/4:1 Not tainted 5.10.0+ #811 [ 104.064000][ T104] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 [ 104.068077][ T104] Workqueue: ipv6_addrconf addrconf_dad_work [ 104.070096][ T104] RIP: 0010:skb_panic+0x15d/0x15f [ 104.072335][ T104] Code: 98 fe 4c 8b 4c 24 10 53 8b 4d 70 45 89 e0 48 c7 c7 60 8b 78 b1 41 57 41 56 41 55 48 8b 54 24 20 48 8b 74 24 28 e8 b5 40 f9 ff <0f> 0b 48 8b 6c 24 20 89 34 24 e8 08 c9 98 fe 8b 34 24 48 c7 c1 80 [ 104.079948][ T104] RSP: 0018:ffff888102557870 EFLAGS: 00010282 [ 104.082361][ T104] RAX: 0000000000000088 RBX: ffff888101c7c000 RCX: 0000000000000000 [ 104.085878][ T104] RDX: 0000000000000088 RSI: 0000000000000008 RDI: ffffed10204aaf05 [ 104.088906][ T104] RBP: ffff8881165f60c0 R08: ffffed102338018d R09: ffffed102338018d [ 104.092111][ T104] R10: ffff888119c00c67 R11: ffffed102338018c R12: 0000000000000008 [ 104.095291][ T104] R13: ffff888009609e90 R14: 0000000000000ec8 R15: 0000000000000ec0 [ 104.098023][ T104] FS: 0000000000000000(0000) GS:ffff888119a00000(0000) knlGS:0000000000000000 [ 104.101532][ T104] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 104.103972][ T104] CR2: 000055a06421b7cc CR3: 000000010d55a002 CR4: 00000000003706e0 [ 104.107058][ T104] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 104.110048][ T104] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 104.113020][ T104] Call Trace: [ 104.114253][ T104] ? mld_newpack+0x4d2/0x8f0 [ 104.115875][ T104] ? mld_newpack+0x4d2/0x8f0 [ 104.117389][ T104] skb_put.cold.104+0x22/0x22 [ 104.118940][ T104] mld_newpack+0x4d2/0x8f0 [ 104.120389][ T104] ? ip6_mc_hdr.isra.25.constprop.47+0x600/0x600 [ 104.122466][ T104] ? register_lock_class+0x1910/0x1910 [ 104.124256][ T104] ? mark_lock.part.46+0xef/0x1c20 [ 104.125925][ T104] add_grhead.isra.32+0x280/0x380 [ 104.127574][ T104] add_grec+0xb13/0xdc0 [ 104.128952][ T104] ? rcu_read_lock_bh_held+0xa0/0xa0 [ ... ] Allowing high order page allocation could fix this problem. Fixes: 72e09ad107e7 ("ipv6: avoid high order allocations") Signed-off-by: Taehee Yoo <ap420...@gmail.com> --- net/ipv6/mcast.c | 3 --- 1 file changed, 3 deletions(-) diff --git a/net/ipv6/mcast.c b/net/ipv6/mcast.c index 6c8604390266..2cab0c563214 100644 --- a/net/ipv6/mcast.c +++ b/net/ipv6/mcast.c @@ -1601,10 +1601,7 @@ static struct sk_buff *mld_newpack(struct inet6_dev *idev, unsigned int mtu) IPV6_TLV_PADN, 0 }; /* we assume size > sizeof(ra) here */ - /* limit our allocations to order-0 page */ - size = min_t(int, size, SKB_MAX_ORDER(0, 0)); skb = sock_alloc_send_skb(sk, size, 1, &err); - if (!skb) return NULL; -- 2.17.1