netdev - Re: [PATCH net] sctp: break out if skb_header_pointer returns NULL in sctp_rcv

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Message-ID: <YU0vSytl5kjXYe9k@t14s.localdomain>
Date:   Thu, 23 Sep 2021 22:52:11 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     network dev <netdev@...r.kernel.org>, davem@...emloft.net,
        kuba@...nel.org, linux-sctp@...r.kernel.org
Subject: Re: [PATCH net] sctp: break out if skb_header_pointer returns NULL
 in sctp_rcv_ootb

On Thu, Sep 23, 2021 at 12:05:04AM -0400, Xin Long wrote:
> We should always check if skb_header_pointer's return is NULL before
> using it, otherwise it may cause null-ptr-deref, as syzbot reported:
> 
>   KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
>   RIP: 0010:sctp_rcv_ootb net/sctp/input.c:705 [inline]
>   RIP: 0010:sctp_rcv+0x1d84/0x3220 net/sctp/input.c:196
>   Call Trace:
>   <IRQ>
>    sctp6_rcv+0x38/0x60 net/sctp/ipv6.c:1109
>    ip6_protocol_deliver_rcu+0x2e9/0x1ca0 net/ipv6/ip6_input.c:422
>    ip6_input_finish+0x62/0x170 net/ipv6/ip6_input.c:463
>    NF_HOOK include/linux/netfilter.h:307 [inline]
>    NF_HOOK include/linux/netfilter.h:301 [inline]
>    ip6_input+0x9c/0xd0 net/ipv6/ip6_input.c:472
>    dst_input include/net/dst.h:460 [inline]
>    ip6_rcv_finish net/ipv6/ip6_input.c:76 [inline]
>    NF_HOOK include/linux/netfilter.h:307 [inline]
>    NF_HOOK include/linux/netfilter.h:301 [inline]
>    ipv6_rcv+0x28c/0x3c0 net/ipv6/ip6_input.c:297
> 
> Fixes: 3acb50c18d8d ("sctp: delay as much as possible skb_linearize")
> Reported-by: syzbot+581aff2ae6b860625116@...kaller.appspotmail.com
> Signed-off-by: Xin Long <lucien.xin@...il.com>

Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>