From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.5 required=3.0 tests=BAYES_00,DKIM_ADSP_CUSTOM_MED, DKIM_INVALID,DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 31842C388F7 for ; Thu, 22 Oct 2020 20:14:18 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 45847241A6 for ; Thu, 22 Oct 2020 20:14:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=google.com header.i=@google.com header.b="vObNVdN2" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 45847241A6 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4CHJVH0h6JzDr1c for ; Fri, 23 Oct 2020 07:14:15 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=google.com (client-ip=2607:f8b0:4864:20::541; helo=mail-pg1-x541.google.com; envelope-from=ndesaulniers@google.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=google.com header.i=@google.com header.a=rsa-sha256 header.s=20161025 header.b=vObNVdN2; dkim-atps=neutral Received: from mail-pg1-x541.google.com (mail-pg1-x541.google.com [IPv6:2607:f8b0:4864:20::541]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4CHJR851tyzDqly for ; Fri, 23 Oct 2020 07:11:32 +1100 (AEDT) Received: by mail-pg1-x541.google.com with SMTP id t14so1660026pgg.1 for ; Thu, 22 Oct 2020 13:11:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=GumHU2X+g85YksdsSI4rtK9zksU56rVy/CgxVuW0jEM=; b=vObNVdN2VFhAojESuCXkrxhn1YIwWVv+1XhIW4tZBL+fxMiFOMf/wpbwdQdbTEuqzU didUUL5vkJxiQnySAkNm5bA5dzi4HDPRY/b2q9PCHYr38o1QdWg4eoCCMy0LZ69odEBE EeVL+yKYldv1+Aa2ZS3w6i1XFzR6cyTrr6WpyCHfwh/bI39Aml+4GPRR3PK53sN4m6b3 rUVDazS3OFa6481GJ9+htMab1H1YbLsr5SViapf30nhQCEj8D6AxmtXaycQnaAAFnPK+ ve/0E2puLZtKaH/rY1wRoNU3uLbs1Hp/JNHjorNUJ0gL9lCRxpciXdv4OO2qkM+X3ZVh gy/g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=GumHU2X+g85YksdsSI4rtK9zksU56rVy/CgxVuW0jEM=; b=MP+TFMPxRZdXMM6AqpwaUAxq4tH+URtgGo51zwnpZ53w20ZGdbAjCSqZHtezPS/IfN 3aVBIqO3DY/gLJDgqwTfZgS33iFpYPRNP6S3DF8fWTkwVXpNkIbfVt2m5qqr3QR1Rqdw skszQdDco+q94LRu+hhDP1W5/ZfngNnRaVh9ADuVUARiizIHtz/ueAGacy9RGOl5d7N3 M9CKPXd/+PwaiGxA7VxpF8ZJ9R5n+9QDhD4BtX0nRbdys83qCTsnO/krIiuV1MJdWYvA X2gqF/nspnXAStegRkzbg/3iLxjbreC27XYJ5nRdjv9xG3JxYtGld2id3ZpN6Kid+uJM LPxQ== X-Gm-Message-State: AOAM532Y+384JwCOZ/ACJ8ray0a6zlUQqkXXJkybYmNLMYGAbf9yrq38 FdYQmA72nI30Cli2YKM8TKUKyM8Rr9e8jRwLFKmoRg== X-Google-Smtp-Source: ABdhPJzJwPfOlPnqmI7/5P7ibjxaxjQ3K/49C5Uiz6yY7FpMEBFECdyjYA4Y8meqnBbTveKDbTZgpESx4RovmeoudXg= X-Received: by 2002:a17:90a:740a:: with SMTP id a10mr3865197pjg.32.1603397486718; Thu, 22 Oct 2020 13:11:26 -0700 (PDT) MIME-Version: 1.0 References: <20201022090155.GA1483166@kroah.com>

<5fd6003b-55a6-2c3c-9a28-8fd3a575ca78@redhat.com> <20201022132342.GB8781@lst.de> <8f1fff0c358b4b669d51cc80098dbba1@AcuMS.aculab.com> <20201022192458.GV3576660@ZenIV.linux.org.uk> In-Reply-To: <20201022192458.GV3576660@ZenIV.linux.org.uk> From: Nick Desaulniers Date: Thu, 22 Oct 2020 13:11:14 -0700 Message-ID: Subject: Re: Buggy commit tracked to: "Re: [PATCH 2/9] iov_iter: move rw_copy_check_uvector() into lib/iov_iter.c" To: Al Viro Content-Type: text/plain; charset="UTF-8" X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "linux-aio@kvack.org" , David Hildenbrand , "linux-mips@vger.kernel.org" , David Howells , "linux-mm@kvack.org" , "keyrings@vger.kernel.org" , "sparclinux@vger.kernel.org" , Christoph Hellwig , "linux-arch@vger.kernel.org" , "linux-s390@vger.kernel.org" , "linux-scsi@vger.kernel.org" , "kernel-team@android.com" , Arnd Bergmann , "linux-block@vger.kernel.org" , "io-uring@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Jens Axboe , "linux-parisc@vger.kernel.org" , Greg KH , "linux-kernel@vger.kernel.org" , "linux-security-module@vger.kernel.org" , David Laight , "netdev@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , Andrew Morton , "linuxppc-dev@lists.ozlabs.org" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Thu, Oct 22, 2020 at 12:25 PM Al Viro wrote: > > On Thu, Oct 22, 2020 at 12:04:52PM -0700, Nick Desaulniers wrote: > > > Passing an `unsigned long` as an `unsigned int` does no such > > narrowing: https://godbolt.org/z/TvfMxe (same vice-versa, just tail > > calls, no masking instructions). > > So if rw_copy_check_uvector() is inlined into import_iovec() (looking > > at the mainline@1028ae406999), then children calls of > > `rw_copy_check_uvector()` will be interpreting the `nr_segs` register > > unmodified, ie. garbage in the upper 32b. > > FWIW, > > void f(unsinged long v) > { > if (v != 1) > printf("failed\n"); > } > > void g(unsigned int v) > { > f(v); > } > > void h(unsigned long v) > { > g(v); > } > > main() > { > h(0x100000001); > } A good/analogous example, but things get weird when the leaf node in the call chain is inline asm: https://godbolt.org/z/s19TY5 (I'm not sure that's precisely what's going on here; I'll need to dive more into the calls rw_copy_check_uvector() makes to see if there's inline asm somewhere, pretty sure calls to get_user with `nr_regs` exist). > > must not produce any output on a host with 32bit int and 64bit long, regardless of > the inlining, having functions live in different compilation units, etc. > > Depending upon the calling conventions, compiler might do truncation in caller or > in a callee, but it must be done _somewhere_. -- Thanks, ~Nick Desaulniers