From: Christoph Hellwig <hch@xxxxxx>
Date: Fri, 24 Jul 2020 08:48:55 +0200
> This sockopt accepts two kinds of parameters, using struct
> sctp_sack_info and struct sctp_assoc_value. The mentioned commit didn't
> notice an implicit cast from the smaller (latter) struct to the bigger
> one (former) when copying the data from the user space, which now leads
> to an attempt to write beyond the buffer (because it assumes the storing
> buffer is bigger than the parameter itself).
>
> Fix it by allocating a sctp_sack_info on stack and filling it out based
> on the small struct for the compat case.
>
> Changelog stole from an earlier patch from Marcelo Ricardo Leitner.
>
> Fixes: ebb25defdc17 ("sctp: pass a kernel pointer to sctp_setsockopt_delayed_ack")
> Reported-by: syzbot+0e4699d000d8b874d8dc@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Applied, thanks.
