Subject: Re: 答复: [PATCH,v2] arm64: fix the illegal address access in some cases

From: Catalin Marinas <[email-masked]>
Date: Tue, 28 Jul 2020 10:53:29 +0100

On Mon, Jul 27, 2020 at 01:29:36PM +0000, Guodeqing (A) wrote:
> > On Sat, Jul 25, 2020 at 10:08:06AM +0800, guodeqing wrote:
> > > The ihl value of ip header is smaller than 5 in some cases, if the ihl
> > > value is smaller than 5, then the next code will access the illegal
> > > address, and the system will panic. ip_fast_csum() must be able to
> > > handle any value that could fit in the ihl field of the ip protocol header.
> > >
> > > Here I add the check of the ihl value to solve this problem.
> > >
> > > Fixes: 0e455d8e80aa (arm64: Implement optimised IP checksum helpers)
> > > Signed-off-by: guodeqing <[email-masked]>
> > > ---
> > >  arch/arm64/include/asm/checksum.h | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/arch/arm64/include/asm/checksum.h
> > > b/arch/arm64/include/asm/checksum.h
> > > index b6f7bc6..5a7d9ac 100644
> > > --- a/arch/arm64/include/asm/checksum.h
> > > +++ b/arch/arm64/include/asm/checksum.h
> > > @@ -25,6 +25,9 @@ static inline __sum16 ip_fast_csum(const void *iph,
> > unsigned int ihl)
> > >  	__uint128_t tmp;
> > >  	u64 sum;
> > >
> > > +	if (unlikely(ihl < 5))
> > > +		return 1;
> > > +
> > >  	tmp = *(const __uint128_t *)iph;
> > >  	iph += 16;
> > >  	ihl -= 4;
> > 
> > IHL in IPv4 should be at least 5. Do you have a stack trace to show how it got
> > here? Maybe the caller should ensure that the correct size is passed.
> 
> If do the following test,this will cause a panic in a arm64 VM. this
> can be reproduced easily.
> 
> ~# ifconfig eth0 up
> ~# ip netns add ns1
> ~# ip link add gw link eth0 type ipvlan 
> ~# ip addr add 168.16.0.1/24 dev gw 
> ~# ip link set dev gw up 
> ~# ip link add ip1 link eth0 type ipvlan 
> ~# ip link set ip1 netns ns1 
> ~# ip netns exec ns1 ip link set ip1 up 
> ~# ip netns exec ns1 ip addr add 168.16.0.2/24 dev ip1 
> ~# ip netns exec ns1 ip link set lo up 
> ~# ip netns exec ns1 ip addr add 127.0.0.1/8 dev lo 
> ~# ip netns exec ns1 tc qdisc add dev ip1 root netem corrupt 100% 
> ~# ip netns exec ns1 ping 168.16.0.1 PING 168.16.0.1

Thanks for the explanation. The fix looks fine to me.

Acked-by: Catalin Marinas <[email-masked]>

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