On Sat, Sep 19, 2020 at 12:12:11AM +0000, Henry Ptasinski wrote:

When calculating ancestor_size with IPv6 enabled, simply using
sizeof(struct ipv6_pinfo) doesn't account for extra bytes needed for
alignment in the struct sctp6_sock. On x86, there aren't any extra
bytes, but on ARM the ipv6_pinfo structure is aligned on an 8-byte
boundary so there were 4 pad bytes that were omitted from the
ancestor_size calculation.  This would lead to corruption of the
pd_lobby pointers, causing an oops when trying to free the sctp
structure on socket close.

Fixes: 636d25d557d1 ("sctp: not copy sctp_sock pd_lobby in sctp_copy_descendant")
Signed-off-by: Henry Ptasinski <redacted>

Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

...

 {
-	int ancestor_size = sizeof(struct inet_sock) +
-			    sizeof(struct sctp_sock) -
-			    offsetof(struct sctp_sock, pd_lobby);
-
-	if (sk_from->sk_family == PF_INET6)
-		ancestor_size += sizeof(struct ipv6_pinfo);
+	size_t ancestor_size = sizeof(struct inet_sock);
 
+	ancestor_size += sk_from->sk_prot->obj_size;

Heh, of course. Nice one.

+	ancestor_size -= offsetof(struct sctp_sock, pd_lobby);
 	__inet_sk_copy_descendant(sk_to, sk_from, ancestor_size);
 }
 
-- 
2.28.0.681.g6f77f65b4e-goog