Subject: Re: [PATCH v3] net: sctp: fix KMSAN uninit-value in sctp_inq_pop

From: Simon Horman <[email-masked]>
Date: Tue, 28 Oct 2025 15:14:28 +0000

On Sun, Oct 26, 2025 at 10:03:12PM +0530, Ranganath V N wrote:
> Fix an issue detected by syzbot:
> 
> KMSAN reported an uninitialized-value access in sctp_inq_pop
> BUG: KMSAN: uninit-value in sctp_inq_pop
> 
> The issue is actually caused by skb trimming via sk_filter() in sctp_rcv().
> In the reproducer, skb->len becomes 1 after sk_filter(), which bypassed the
> original check:
> 
>         if (skb->len < sizeof(struct sctphdr) + sizeof(struct sctp_chunkhdr) +
>                        skb_transport_offset(skb))
> To handle this safely, a new check should be performed after sk_filter().
> 
> Reported-by: [email-masked]
> Tested-by: [email-masked]
> Closes: https://syzkaller.appspot.com/bug?extid=d101e12bccd4095460e7
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Suggested-by: Xin Long <[email-masked]>
> Signed-off-by: Ranganath V N <[email-masked]>
> ---
> KMSAN reported an uninitialized-value access in sctp_inq_pop
> ---
> Changes in v3:
> - fixes the patch format like fixes and closes tags.
> - Link to v2: https://lore.kernel.org/r/[email-masked]

Thanks for the update. This version looks good to me.
And I assume it is for net.

Reviewed-by: Simon Horman <[email-masked]>