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

[Simon Horman]

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: syzbot+d101e12bccd4095460e7@xxxxxxxxxxxxxxxxxxxxxxxxx
> Tested-by: syzbot+d101e12bccd4095460e7@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=d101e12bccd4095460e7
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Suggested-by: Xin Long <lucien.xin@xxxxxxxxx>
> Signed-off-by: Ranganath V N <vnranganath.20@xxxxxxxxx>
> ---
> 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/20251024-kmsan_fix-v2-1-dc393cfb9071@xxxxxxxxx

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

Reviewed-by: Simon Horman <horms@xxxxxxxxxx>