commit 68a1fdbb upstream.

The ASN.1 parser does not necessarily set the sinfo field,
this patch prevents a NULL pointer dereference on broken
input.

Fixes: 99db4435 ("PKCS#7: Appropriately restrict authenticated attributes and content type")
Signed-off-by: Eric Sesterhenn <eric.sesterhenn@x41-dsec.de>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>