Re: "Kernel Warn in af_inet" in Linux Kernel Version 2.6.26

[Eric Dumazet <eric.dumazet@gmail.com>]

On 12/2/24 5:30 AM, cheung wall wrote:
> Hello,
>
> I am writing to report a potential vulnerability identified in the
> Linux Kernel version 2.6.26.
> This issue was discovered using our custom vulnerability discovery
> tool.
>
> Affected File:
>
> File: net/ipv4/af_inet.c
>
> Detailed call trace:
>
> [ 1788.473836] KERNEL: assertion (!atomic_read(&sk->sk_wmem_alloc))
> failed at net/ipv4/af_inet.c (155)
> [ 1788.473836] KERNEL: assertion (!sk->sk_wmem_queued) failed at
> net/ipv4/af_inet.c (156)
> [ 1788.473836] KERNEL: assertion (!sk->sk_forward_alloc) failed at
> net/ipv4/af_inet.c (157)
> [ 1788.473836] KERNEL: assertion (!atomic_read(&sk->sk_wmem_alloc))
> failed at net/ipv4/af_inet.c (155)
> [ 1788.473836] KERNEL: assertion (!sk->sk_wmem_queued) failed at
> net/ipv4/af_inet.c (156)
> [ 1788.473862] KERNEL: assertion (!sk->sk_forward_alloc) failed at
> net/ipv4/af_inet.c (157)
>
> Repro C Source Code: https://pastebin.com/qs5y6Bcy
>
> Root Cause:
>
> The root cause of this bug lies in the improper handling of socket
> write memory management in the IPv4 stack, specifically in the
> assertions within net/ipv4/af_inet.c. The PoC triggers a sequence of
> socket operations, including socket, sendto, listen, and accept, with
> crafted input data and parameters. These operations result in
> inconsistent states of the sock structure, where critical fields like
> sk_wmem_alloc, sk_wmem_queued, and sk_forward_alloc are not properly
> cleared or synchronized. The kernel fails to maintain the expected
> invariants for these fields, leading to assertion failures that
> indicate a logical inconsistency in memory allocation or deallocation
> for socket operations. This issue highlights a potential lack of
> proper cleanup or state transition checks in the network stack.


Please do not fuzz old and not supported kernels.

Or do not report to us the issues, _unless_ they also trigger on 
recent/supported kernels.

Thank you.