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=-4.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 0C525C433E2 for ; Wed, 20 May 2020 11:11:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D25B7207D3 for ; Wed, 20 May 2020 11:11:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589973094; bh=CZO2oVmSFplMBz9Hp/Ib++cLu93ut1vlEwhwSgDctvg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=lIlsO2yu/F02rXO8n5C9fHB4KjxMe7LUSoXmJd9eE8XCopZVzjOE72oVxlPHglCPS Vwh5laiBVlWg30ZcM4PCNVv1/EcydZo4LO+qCajDl5X2/C+Un9o7nX/UVy4DIsTX7k NrflsN1Knp5ooWLpaTpKWNHIn7WcQIA/tD0RZbHg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726868AbgETLLe (ORCPT ); Wed, 20 May 2020 07:11:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:56474 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726859AbgETLLc (ORCPT ); Wed, 20 May 2020 07:11:32 -0400 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6429E207C4; Wed, 20 May 2020 11:11:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1589973091; bh=CZO2oVmSFplMBz9Hp/Ib++cLu93ut1vlEwhwSgDctvg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=0JQBodzpZZsofv0Hjk8g+YCto+yzr1HnJmp8bkaaHFsZdNStcwkqu6sxB/Cq7RGNZ D9oyW+ivG0VvZVxdbnNjqnjrKg4ZFxKYuPou20DYf2dxIBIfJoUskwUkakdJdMZzgW O2b3pTDEl9xo3o3HjCuYb8IrGfvnz8+E0HAxmEdI= Date: Wed, 20 May 2020 20:11:26 +0900 From: Masami Hiramatsu To: Christoph Hellwig Cc: x86@kernel.org, Alexei Starovoitov , Daniel Borkmann , Linus Torvalds , Andrew Morton , linux-parisc@vger.kernel.org, linux-um@lists.infradead.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 13/20] maccess: always use strict semantics for probe_kernel_read Message-Id: <20200520201126.f37d3b1e46355199216404e2@kernel.org> In-Reply-To: <20200519134449.1466624-14-hch@lst.de> References: <20200519134449.1466624-1-hch@lst.de> <20200519134449.1466624-14-hch@lst.de> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org On Tue, 19 May 2020 15:44:42 +0200 Christoph Hellwig wrote: > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index 2f6737cc53e6c..82da20e712507 100644 > --- a/kernel/trace/trace_kprobe.c > +++ b/kernel/trace/trace_kprobe.c > @@ -1208,7 +1208,13 @@ fetch_store_strlen(unsigned long addr) > u8 c; > > do { > - ret = probe_kernel_read(&c, (u8 *)addr + len, 1); > + if (IS_ENABLED(CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE) && > + (unsigned long)addr < TASK_SIZE) { > + ret = probe_user_read(&c, > + (__force u8 __user *)addr + len, 1); > + } else { > + ret = probe_kernel_read(&c, (u8 *)addr + len, 1); > + } > len++; > } while (c && ret == 0 && len < MAX_STRING_SIZE); To avoid redundant check in the loop, we can use strnlen_user_nofault() out of the loop. Something like below. ... u8 c; if (IS_ENABLED(CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE) && (unsigned long)addr < TASK_SIZE) { return strnlen_user_nofault((__force u8 __user *)addr, MAX_STRING_SIZE); do { ret = probe_kernel_read(&c, (u8 *)addr + len, 1); len++; } while (c && ret == 0 && len < MAX_STRING_SIZE); ... This must work because we must not have a string that continues across kernel　space and user space. Thank you, -- Masami Hiramatsu From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jbMdI-0003mp-Hw for linux-um@lists.infradead.org; Wed, 20 May 2020 11:11:34 +0000 Date: Wed, 20 May 2020 20:11:26 +0900 From: Masami Hiramatsu Subject: Re: [PATCH 13/20] maccess: always use strict semantics for probe_kernel_read Message-Id: <20200520201126.f37d3b1e46355199216404e2@kernel.org> In-Reply-To: <20200519134449.1466624-14-hch@lst.de> References: <20200519134449.1466624-1-hch@lst.de> <20200519134449.1466624-14-hch@lst.de> Mime-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-um" Errors-To: linux-um-bounces+geert=linux-m68k.org@lists.infradead.org To: Christoph Hellwig Cc: linux-parisc@vger.kernel.org, Daniel Borkmann , netdev@vger.kernel.org, x86@kernel.org, linux-um@lists.infradead.org, Alexei Starovoitov , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Linus Torvalds , bpf@vger.kernel.org T24gVHVlLCAxOSBNYXkgMjAyMCAxNTo0NDo0MiArMDIwMApDaHJpc3RvcGggSGVsbHdpZyA8aGNo QGxzdC5kZT4gd3JvdGU6Cgo+IGRpZmYgLS1naXQgYS9rZXJuZWwvdHJhY2UvdHJhY2Vfa3Byb2Jl LmMgYi9rZXJuZWwvdHJhY2UvdHJhY2Vfa3Byb2JlLmMKPiBpbmRleCAyZjY3MzdjYzUzZTZjLi44 MmRhMjBlNzEyNTA3IDEwMDY0NAo+IC0tLSBhL2tlcm5lbC90cmFjZS90cmFjZV9rcHJvYmUuYwo+ ICsrKyBiL2tlcm5lbC90cmFjZS90cmFjZV9rcHJvYmUuYwo+IEBAIC0xMjA4LDcgKzEyMDgsMTMg QEAgZmV0Y2hfc3RvcmVfc3RybGVuKHVuc2lnbmVkIGxvbmcgYWRkcikKPiAgCXU4IGM7Cj4gIAo+ ICAJZG8gewo+IC0JCXJldCA9IHByb2JlX2tlcm5lbF9yZWFkKCZjLCAodTggKilhZGRyICsgbGVu LCAxKTsKPiArCQlpZiAoSVNfRU5BQkxFRChDT05GSUdfQVJDSF9IQVNfTk9OX09WRVJMQVBQSU5H X0FERFJFU1NfU1BBQ0UpICYmCj4gKwkJICAgICh1bnNpZ25lZCBsb25nKWFkZHIgPCBUQVNLX1NJ WkUpIHsKPiArCQkJcmV0ID0gcHJvYmVfdXNlcl9yZWFkKCZjLAo+ICsJCQkJKF9fZm9yY2UgdTgg X191c2VyICopYWRkciArIGxlbiwgMSk7Cj4gKwkJfSBlbHNlIHsKPiArCQkJcmV0ID0gcHJvYmVf a2VybmVsX3JlYWQoJmMsICh1OCAqKWFkZHIgKyBsZW4sIDEpOwo+ICsJCX0KPiAgCQlsZW4rKzsK PiAgCX0gd2hpbGUgKGMgJiYgcmV0ID09IDAgJiYgbGVuIDwgTUFYX1NUUklOR19TSVpFKTsKClRv IGF2b2lkIHJlZHVuZGFudCBjaGVjayBpbiB0aGUgbG9vcCwgd2UgY2FuIHVzZSBzdHJubGVuX3Vz ZXJfbm9mYXVsdCgpIG91dCBvZgp0aGUgbG9vcC4gU29tZXRoaW5nIGxpa2UgYmVsb3cuCgouLi4K CXU4IGM7CgoJaWYgKElTX0VOQUJMRUQoQ09ORklHX0FSQ0hfSEFTX05PTl9PVkVSTEFQUElOR19B RERSRVNTX1NQQUNFKSAmJgoJICAgICh1bnNpZ25lZCBsb25nKWFkZHIgPCBUQVNLX1NJWkUpIHsK CQlyZXR1cm4gc3Rybmxlbl91c2VyX25vZmF1bHQoKF9fZm9yY2UgdTggX191c2VyICopYWRkciwg TUFYX1NUUklOR19TSVpFKTsKCglkbyB7CgkJcmV0ID0gcHJvYmVfa2VybmVsX3JlYWQoJmMsICh1 OCAqKWFkZHIgKyBsZW4sIDEpOwoJCWxlbisrOwoJfSB3aGlsZSAoYyAmJiByZXQgPT0gMCAmJiBs ZW4gPCBNQVhfU1RSSU5HX1NJWkUpOwouLi4KClRoaXMgbXVzdCB3b3JrIGJlY2F1c2Ugd2UgbXVz dCBub3QgaGF2ZSBhIHN0cmluZyB0aGF0IGNvbnRpbnVlcyBhY3Jvc3MKa2VybmVs44CAc3BhY2Ug YW5kIHVzZXIgc3BhY2UuCgpUaGFuayB5b3UsCgoKLS0gCk1hc2FtaSBIaXJhbWF0c3UgPG1oaXJh bWF0QGtlcm5lbC5vcmc+CgpfX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fXwpsaW51eC11bSBtYWlsaW5nIGxpc3QKbGludXgtdW1AbGlzdHMuaW5mcmFkZWFkLm9y ZwpodHRwOi8vbGlzdHMuaW5mcmFkZWFkLm9yZy9tYWlsbWFuL2xpc3RpbmZvL2xpbnV4LXVtCg==