From: Martin KaFai Lau <[email protected]>
Date: Mon, 18 May 2020 17:13:34 -0700
> The commit 637bc8bbe6c0 ("inet: reset tb->fastreuseport when adding a
> reuseport sk")
> added a bind-address cache in tb->fast*. The tb->fast* caches the address
> of a sk which has successfully been binded with SO_REUSEPORT ON. The idea
> is to avoid the expensive conflict search in inet_csk_bind_conflict().
>
> There is an issue with wildcard matching where sk_reuseport_match() should
> have returned false but it is currently returning true. It ends up
> hiding bind conflict. For example,
>
> bind("[::1]:443"); /* without SO_REUSEPORT. Succeed. */
> bind("[::2]:443"); /* with SO_REUSEPORT. Succeed. */
> bind("[::]:443"); /* with SO_REUSEPORT. Still Succeed where it shouldn't
> */
>
> The last bind("[::]:443") with SO_REUSEPORT on should have failed because
> it should have a conflict with the very first bind("[::1]:443") which
> has SO_REUSEPORT off. However, the address "[::2]" is cached in
> tb->fast* in the second bind. In the last bind, the sk_reuseport_match()
> returns true because the binding sk's wildcard addr "[::]" matches with
> the "[::2]" cached in tb->fast*.
>
> The correct bind conflict is reported by removing the second
> bind such that tb->fast* cache is not involved and forces the
> bind("[::]:443") to go through the inet_csk_bind_conflict():
>
> bind("[::1]:443"); /* without SO_REUSEPORT. Succeed. */
> bind("[::]:443"); /* with SO_REUSEPORT. -EADDRINUSE */
>
> The expected behavior for sk_reuseport_match() is, it should only allow
> the "cached" tb->fast* address to be used as a wildcard match but not
> the address of the binding sk. To do that, the current
> "bool match_wildcard" arg is split into
> "bool match_sk1_wildcard" and "bool match_sk2_wildcard".
>
> This change only affects the sk_reuseport_match() which is only
> used by inet_csk (e.g. TCP).
> The other use cases are calling inet_rcv_saddr_equal() and
> this patch makes it pass the same "match_wildcard" arg twice to
> the "ipv[46]_rcv_saddr_equal(..., match_wildcard, match_wildcard)".
>
> Cc: Josef Bacik <[email protected]>
> Fixes: 637bc8bbe6c0 ("inet: reset tb->fastreuseport when adding a reuseport
> sk")
> Signed-off-by: Martin KaFai Lau <[email protected]>
Applied and queued up for -stable, thanks.
