Re: [PATCH stable v5.4 2/2] IPv6: reply ICMP error if the first fragment don't include all headers

[Greg KH]

On Sat, Jan 30, 2021 at 05:24:52PM +0530, Aviraj CJ wrote:
> From: Hangbin Liu <liuhangbin@xxxxxxxxx>
> 
> commit 2efdaaaf883a143061296467913c01aa1ff4b3ce upstream.
> 
> Based on RFC 8200, Section 4.5 Fragment Header:
> 
>   -  If the first fragment does not include all headers through an
>      Upper-Layer header, then that fragment should be discarded and
>      an ICMP Parameter Problem, Code 3, message should be sent to
>      the source of the fragment, with the Pointer field set to zero.
> 
> Checking each packet header in IPv6 fast path will have performance impact,
> so I put the checking in ipv6_frag_rcv().
> 
> As the packet may be any kind of L4 protocol, I only checked some common
> protocols' header length and handle others by (offset + 1) > skb->len.
> Also use !(frag_off & htons(IP6_OFFSET)) to catch atomic fragments
> (fragmented packet with only one fragment).
> 
> When send ICMP error message, if the 1st truncated fragment is ICMP message,
> icmp6_send() will break as is_ineligible() return true. So I added a check
> in is_ineligible() to let fragment packet with nexthdr ICMP but no ICMP header
> return false.
> 
> Signed-off-by: Hangbin Liu <liuhangbin@xxxxxxxxx>
> Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
> Signed-off-by: Aviraj CJ <acj@xxxxxxxxx>
> ---
>  net/ipv6/icmp.c       |  8 +++++++-
>  net/ipv6/reassembly.c | 33 ++++++++++++++++++++++++++++++++-
>  2 files changed, 39 insertions(+), 2 deletions(-)

Both now queued up, thanks.

greg k-h