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Thu, 22 Oct 2020 13:54:20 -0400 Received: from mail-pl1-x642.google.com (mail-pl1-x642.google.com [IPv6:2607:f8b0:4864:20::642]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 00A71C0613D8 for ; Thu, 22 Oct 2020 10:54:19 -0700 (PDT) Received: by mail-pl1-x642.google.com with SMTP id w11so1351667pll.8 for ; Thu, 22 Oct 2020 10:54:19 -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=fN98WKFQMgEXMlp8i3NGUVnGVw+6y+e2V0ke9rhUWSA=; b=BKV40KcFYv/RT7WI/LzYvQYye/7QuyEZeVOFKBpWDRGSNerYyXtKTvLxKg7AQQyR6a B6ov6UgSF+CT0yFZ5Kpm//JhG6JX+erMmrvxUD0nM2EPok7DJ1dyb0csZXVH+J57G76o JEKNKLPukNE3mXje8tahLR4x5JyOobyLEq7zPqSmgsU53Cxt6nYjuHUBVcdVMcbrcilK K/V95Mavbng7Vx66laYlk4QUwTrTI6xWi8qckIoCQ5E2cwAi2ki1g0yQJTA0k1YggZ8N +hx8KG1AyjINmebjC8dKCAdqeNm9iI1l37J/7olC9z6B/lTJyWVJjteE9X9SnKXuuDmh S8ew== 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=fN98WKFQMgEXMlp8i3NGUVnGVw+6y+e2V0ke9rhUWSA=; b=e4QOAk/FBzdiCYOKaxgcy3ukzL7uLPnQjM5agZy0QA/ReCSOdpAgSdm5H8L+T9S5zA ly3UX6v1onorPw+8YILGQbLkNrcfSTMWWESpL5QziwKSCVZ8wDwVP8jPWfBxBqHSXZyc ArFhL606D6gDNgNUPe4arxppxVtGjXcop5Ae+PFu6JloFugjudOdkVXPTHnWsaUzH2wE PN1iC5DRkac32RzZoqNNWYkKs2uEIa76rEdpp+jYo+7X6bhR82e6QcDwJulEC9eM18py 1QuFZgj9UymLNAdD++t7Th6ipS3ypu9nZbMZktUGtYRYJcqWkHAteeJ3pDEgyN1NdjYF QFJw== X-Gm-Message-State: AOAM531+SWOZd/Xf5ou4VbkXVHQahNWlmaeyCR0VsLmZSdxKtEfCWFZc Ghhgxn4u14Bp5lBM90/vfnLcTQ6R6mgE6f21Iu0Nmw== X-Google-Smtp-Source: ABdhPJwKMlfWHWIfBAFNm3K11R3iXcLN/39e27pMOK/669Q9lQtbTX5Z9LF4v87HnqXK2It7QLj5rkKD4/EUsxOxOjE= X-Received: by 2002:a17:902:c40b:b029:d3:def2:d90f with SMTP id k11-20020a170902c40bb02900d3def2d90fmr3352248plk.29.1603389258899; Thu, 22 Oct 2020 10:54:18 -0700 (PDT) MIME-Version: 1.0 References: <20201021233914.GR3576660@ZenIV.linux.org.uk> <20201022082654.GA1477657@kroah.com> <80a2e5fa-718a-8433-1ab0-dd5b3e3b5416@redhat.com> <5d2ecb24db1e415b8ff88261435386ec@AcuMS.aculab.com> <20201022090155.GA1483166@kroah.com> <5fd6003b-55a6-2c3c-9a28-8fd3a575ca78@redhat.com> <20201022132342.GB8781@lst.de> <8f1fff0c358b4b669d51cc80098dbba1@AcuMS.aculab.com> In-Reply-To: <8f1fff0c358b4b669d51cc80098dbba1@AcuMS.aculab.com> From: Nick Desaulniers Date: Thu, 22 Oct 2020 10:54:06 -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: David Laight Cc: Christoph Hellwig , David Hildenbrand , Greg KH , Al Viro , "kernel-team@android.com" , Andrew Morton , Jens Axboe , Arnd Bergmann , David Howells , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-mips@vger.kernel.org" , "linux-parisc@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-s390@vger.kernel.org" , "sparclinux@vger.kernel.org" , "linux-block@vger.kernel.org" , "linux-scsi@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-aio@kvack.org" , "io-uring@vger.kernel.org" , "linux-arch@vger.kernel.org" , "linux-mm@kvack.org" , "netdev@vger.kernel.org" , "keyrings@vger.kernel.org" , "linux-security-module@vger.kernel.org" Content-Type: multipart/mixed; boundary="0000000000003743e505b2462753" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org --0000000000003743e505b2462753 Content-Type: text/plain; charset="UTF-8" On Thu, Oct 22, 2020 at 9:35 AM David Laight wrote: > > From: Christoph Hellwig > > Sent: 22 October 2020 14:24 > > > > On Thu, Oct 22, 2020 at 11:36:40AM +0200, David Hildenbrand wrote: > > > My thinking: if the compiler that calls import_iovec() has garbage in > > > the upper 32 bit > > > > > > a) gcc will zero it out and not rely on it being zero. > > > b) clang will not zero it out, assuming it is zero. > > > > > > But > > > > > > a) will zero it out when calling the !inlined variant > > > b) clang will zero it out when calling the !inlined variant > > > > > > When inlining, b) strikes. We access garbage. That would mean that we > > > have calling code that's not generated by clang/gcc IIUC. > > > > Most callchains of import_iovec start with the assembly syscall wrappers. > > Wait... > readv(2) defines: > ssize_t readv(int fd, const struct iovec *iov, int iovcnt); > > But the syscall is defined as: > > SYSCALL_DEFINE3(readv, unsigned long, fd, const struct iovec __user *, vec, > unsigned long, vlen) > { > return do_readv(fd, vec, vlen, 0); > } > > I'm guessing that nothing actually masks the high bits that come > from an application that is compiled with clang? > > The vlen is 'unsigned long' through the first few calls. > So unless there is a non-inlined function than takes vlen > as 'int' the high garbage bits from userspace are kept. Yeah, that's likely a bug: https://godbolt.org/z/KfsPKs > > Which makes it a bug in the kernel C syscall wrappers. > They need to explicitly mask the high bits of 32bit > arguments on arm64 but not x86-64. Why not x86-64? Wouldn't it be *any* LP64 ISA? Attaching a patch that uses the proper width, but I'm pretty sure there's still a signedness issue . Greg, would you mind running this through the wringer? > > What does the ARM EABI say about register parameters? AAPCS is the ABI for 64b ARM, IIUC, which is the ISA GKH is reporting the problem against. IIUC, EABI is one of the 32b ABIs. aarch64 is LP64 just like x86_64. -- Thanks, ~Nick Desaulniers --0000000000003743e505b2462753 Content-Type: application/octet-stream; name="0001-fs-fix-up-type-confusion-in-readv-writev.patch" Content-Disposition: attachment; filename="0001-fs-fix-up-type-confusion-in-readv-writev.patch" Content-Transfer-Encoding: base64 Content-ID: X-Attachment-Id: f_kgl4e4rn0 RnJvbSBhYWUyNmIxM2ZmYjllMzhiYjQ2YjhjODU5ODU3NjFiNWYxOTZiNmY2IE1vbiBTZXAgMTcg MDA6MDA6MDAgMjAwMQpGcm9tOiBOaWNrIERlc2F1bG5pZXJzIDxuZGVzYXVsbmllcnNAZ29vZ2xl LmNvbT4KRGF0ZTogVGh1LCAyMiBPY3QgMjAyMCAxMDoyMzo0NyAtMDcwMApTdWJqZWN0OiBbUEFU Q0hdIGZzOiBmaXggdXAgdHlwZSBjb25mdXNpb24gaW4gcmVhZHYvd3JpdGV2CgpUaGUgc3lzY2Fs bCBpbnRlcmZhY2UgZG9lc24ndCBtYXRjaCB1cCB3aXRoIHRoZSBpbnRlcmZhY2UgbGliYyBpcyB1 c2luZwpvciB0aGF0J3MgZGVmaW5lZCBpbiB0aGUgbWFudWFsIHBhZ2VzLgoKc3NpemVfdCByZWFk dihpbnQgZmQsIGNvbnN0IHN0cnVjdCBpb3ZlYyAqaW92LCBpbnQgaW92Y250KTsKc3NpemVfdCB3 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