buglwIP - A Lightweight TCP/IP stack - Bugs: bug #57374, Assertion "this needs a pbuf...


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bug #57374: Assertion "this needs a pbuf in one piece!" failed

Submitted by:  Hiromasa Ito <vhertz>
Submitted on:  Sat 07 Dec 2019 01:11:02 PM UTC  
Category:  IPv6 Severity:  3 - Normal
Item Group:  Crash Error Status:  None
Privacy:  Public Assigned to:  None
Open/Closed:  Open Planned Release:  None
lwIP version:  Other

Sun 08 Dec 2019 01:35:45 AM UTC, comment #1: 

Sorry, the following sentence is not correct.

> If `p` has only IPv6 datagrams, it can have payloads that are less than IP6_HLEN.


If `p` has only IPv6 payloads, its length can be less than IP6_HLEN.

Hiromasa Ito <vhertz>
Sat 07 Dec 2019 01:11:02 PM UTC, original submission:  

Hi, all.

This is one of the assertion failures I found by fuzzing (to lwIP ver2.1.0.RC1).
The following LWIP_ASSERT() at lwip/src/core/ipv6/ip6_frag.c:784 fails.

LWIP_ASSERT("this needs a pbuf in one piece!", (p->len >= (IP6_HLEN)));

I think this assert is not always true.
If `p` is a pbuf chain, The only first pbuf has the IPv6 header.
If `p` has only IPv6 datagrams, it can have payloads that are less than IP6_HLEN.

You can reproduce this failure with 'crashed_inputs/003' attached to the following message of lwip-devel:

Hiromasa Ito <vhertz>


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