Messages in this thread | | | From | Eric Dumazet <> | Date | Fri, 28 Jul 2023 12:50:22 +0200 | Subject | Re: [PATCH] ip6mr: Fix skb_under_panic in ip6mr_cache_report() |
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On Fri, Jul 28, 2023 at 12:01 PM Yue Haibing <yuehaibing@huawei.com> wrote: > > skbuff: skb_under_panic: text:ffffffff88771f69 len:56 put:-4 > head:ffff88805f86a800 data:ffff887f5f86a850 tail:0x88 end:0x2c0 dev:pim6reg > ------------[ cut here ]------------ >
> When setup a vlan device on dev pim6reg, DAD ns packet may sent on reg_vif_xmit(). > reg_vif_xmit() > ip6mr_cache_report() > skb_push(skb, -skb_network_offset(pkt));//skb_network_offset(pkt) is 4 > And skb_push declar as this: > void *skb_push(struct sk_buff *skb, unsigned int len); > skb->data -= len; > //0xffff888f5f86a84c - 0xfffffffc = 0xffff887f5f86a850 > skb->data is set to 0xffff887f5f86a850, which is invalid mem addr, lead to skb_push() fails. > > Fixes: 14fb64e1f449 ("[IPV6] MROUTE: Support PIM-SM (SSM).") > Signed-off-by: Yue Haibing <yuehaibing@huawei.com> > --- > net/ipv6/ip6mr.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c > index cc3d5ad17257..ee9c2ff8b0e4 100644 > --- a/net/ipv6/ip6mr.c > +++ b/net/ipv6/ip6mr.c > @@ -1051,9 +1051,9 @@ static int ip6mr_cache_report(const struct mr_table *mrt, struct sk_buff *pkt, > int ret; > > #ifdef CONFIG_IPV6_PIMSM_V2 > + int nhoff = skb_network_offset(pkt); > if (assert == MRT6MSG_WHOLEPKT || assert == MRT6MSG_WRMIFWHOLE) > - skb = skb_realloc_headroom(pkt, -skb_network_offset(pkt) > - +sizeof(*msg)); > + skb = skb_realloc_headroom(pkt, -nhoff + sizeof(*msg)); > else > #endif > skb = alloc_skb(sizeof(struct ipv6hdr) + sizeof(*msg), GFP_ATOMIC); > @@ -1073,7 +1073,8 @@ static int ip6mr_cache_report(const struct mr_table *mrt, struct sk_buff *pkt, > And all this only to mangle msg->im6_msgtype and > to set msg->im6_mbz to "mbz" :-) > */ > - skb_push(skb, -skb_network_offset(pkt)); > + skb->data += nhoff; > + skb->len -= nhoff;
__skb_pull(skb, nhoff);
> > skb_push(skb, sizeof(*msg)); > skb_reset_transport_header(skb); > -- > 2.34.1 >
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