From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AD25F1879 for ; Tue, 4 Jul 2023 08:51:04 +0000 (UTC) Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C6050E47 for ; Tue, 4 Jul 2023 01:51:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1688460661; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=zdyxwyfyCuKz7/7BHOPg3TNF1zFyGIHGDllKl8O41gE=; b=jWLJsInSvF2oQRYBtZVnQXYo9ad8f3p/vbrHwX22TaNyURQwDp3CAakXpet1GOrR6vl5Lx 2/E1HvdC13vRogDhmmIfberkUnhEQUO7qIV8SA9sAwEaKGY/+7ez5GtY2e7m8YiPMSZFIF /AxUbjnbd0wnYF6BxGVyY4TGIjYJ6Ik= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-472-75wUcZQuO5O7AiS-mVACww-1; Tue, 04 Jul 2023 04:50:58 -0400 X-MC-Unique: 75wUcZQuO5O7AiS-mVACww-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5FE6F1044590; Tue, 4 Jul 2023 08:50:58 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.42.28.195]) by smtp.corp.redhat.com (Postfix) with ESMTP id 14DE62166B34; Tue, 4 Jul 2023 08:50:38 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: To: Ondrej Mosnacek Cc: dhowells@redhat.com, Linux Crypto Mailing List , Herbert Xu , Paolo Abeni , netdev@vger.kernel.org Subject: Re: Regression bisected to "crypto: af_alg: Convert af_alg_sendpage() to use MSG_SPLICE_PAGES" Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <1357759.1688460637.1@warthog.procyon.org.uk> Date: Tue, 04 Jul 2023 09:50:37 +0100 Message-ID: <1357760.1688460637@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H4,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE, T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net One problem with libkcapi is that it's abusing vmsplice(). It must not use vmsplice(SPLICE_F_GIFT) on a buffer that's in the heap. To quote the manual page: The user pages are a gift to the kernel. The application may not modify this memory ever, otherwise the page cache and on- disk data may differ. Gifting pages to the kernel means that a subsequent splice(2) SPLICE_F_MOVE can successfully move the pages; if this flag is not specified, then a subsequent splice(2) SPLICE_F_MOVE must copy the pages. Data must also be properly page aligned, both in memory and length. Basically, this can destroy the integrity of the process's heap as the allocator may have metadata there that then gets excised. If I remove the flag, it still crashes, so that's not the only problem. David