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=-9.5 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham 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 D2FF8C47259 for ; Wed, 6 May 2020 06:23:05 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8C60720753 for ; Wed, 6 May 2020 06:23:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="ZxEYLUlt" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8C60720753 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3657B8E0011; Wed, 6 May 2020 02:23:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2ED1F8E0003; Wed, 6 May 2020 02:23:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1DD508E0011; Wed, 6 May 2020 02:23:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0225.hostedemail.com [216.40.44.225]) by kanga.kvack.org (Postfix) with ESMTP id 00EDC8E0010 for ; Wed, 6 May 2020 02:23:04 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id C37B72AAE for ; Wed, 6 May 2020 06:23:04 +0000 (UTC) X-FDA: 76785301488.26.beds77_1ad5f73dd7223 X-HE-Tag: beds77_1ad5f73dd7223 X-Filterd-Recvd-Size: 9580 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf15.hostedemail.com (Postfix) with ESMTP for ; Wed, 6 May 2020 06:23:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description; bh=YnqX7e3iRi8ZqyWswsRov2ifnOnli5oxUPAyZD7RiOM=; b=ZxEYLUltG837WhX+M/tX7SRXnu XS4J8moBK/3WJoZQ9jHvR1LC4B+8LFrluqTS34YHh1pNIZhG9NpgATarDepP5bZdooaH17iAwzC2p 5olJSsxatR9oxLTiTlgHfY6ihPw4iRPJVIP554HpcO2y3K1V5dIAKVJHha+QQYMTbxR8NR5cy/KCY K2sJPH93axSP4b1twvO5hg467TJ9WE9oEpEKBwzyIVrMpGtdU7cCe7fyYPZJRtvmiqbSwu2VAvEeR 3GQZqabeM3nEz5uyRdI2TxVkmQ8PFoydByNQPyK72tr/7eQUSbXzKEYbFDo92qPTOVVCb2O+OaCuJ HFzcjt5g==; Received: from [2001:4bb8:191:66b6:c70:4a89:bc61:2] (helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jWDSP-0006n7-Lf; Wed, 06 May 2020 06:23:02 +0000 From: Christoph Hellwig To: x86@kernel.org, Alexei Starovoitov , Daniel Borkmann , Masami Hiramatsu , Linus Torvalds , Andrew Morton Cc: 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: [PATCH 12/15] maccess: always use strict semantics for probe_kernel_read Date: Wed, 6 May 2020 08:22:20 +0200 Message-Id: <20200506062223.30032-13-hch@lst.de> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200506062223.30032-1-hch@lst.de> References: <20200506062223.30032-1-hch@lst.de> MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Except for historical confusion in the kprobes/uprobes and bpf tracers there is no good reason to ever allow user memory accesses from probe_kernel_read. Make the tracers fall back to a probe_user_read if the probe_kernel_read falls to keep the core API clean. Signed-off-by: Christoph Hellwig --- arch/parisc/lib/memcpy.c | 3 +-- arch/um/kernel/maccess.c | 3 +-- arch/x86/mm/maccess.c | 5 +---- include/linux/uaccess.h | 4 +--- kernel/trace/bpf_trace.c | 20 +++++++++++++------ kernel/trace/trace_kprobe.c | 11 ++++++++++- mm/maccess.c | 39 ++++++------------------------------- 7 files changed, 34 insertions(+), 51 deletions(-) diff --git a/arch/parisc/lib/memcpy.c b/arch/parisc/lib/memcpy.c index 5ef648bd33119..9fe662b3b5604 100644 --- a/arch/parisc/lib/memcpy.c +++ b/arch/parisc/lib/memcpy.c @@ -57,8 +57,7 @@ void * memcpy(void * dst,const void *src, size_t count) EXPORT_SYMBOL(raw_copy_in_user); EXPORT_SYMBOL(memcpy); =20 -bool probe_kernel_read_allowed(void *dst, const void *unsafe_src, size_t= size, - bool strict) +bool probe_kernel_read_allowed(void *dst, const void *unsafe_src, size_t= size) { if ((unsigned long)unsafe_src < PAGE_SIZE) return false; diff --git a/arch/um/kernel/maccess.c b/arch/um/kernel/maccess.c index 90a1bec923158..734f3d7e57c0f 100644 --- a/arch/um/kernel/maccess.c +++ b/arch/um/kernel/maccess.c @@ -7,8 +7,7 @@ #include #include =20 -bool probe_kernel_read_allowed(void *dst, const void *src, size_t size, - bool strict) +bool probe_kernel_read_allowed(void *dst, const void *src, size_t size) { void *psrc =3D (void *)rounddown((unsigned long)src, PAGE_SIZE); =20 diff --git a/arch/x86/mm/maccess.c b/arch/x86/mm/maccess.c index 5c323ab187b27..a1bd81677aa72 100644 --- a/arch/x86/mm/maccess.c +++ b/arch/x86/mm/maccess.c @@ -26,10 +26,7 @@ static __always_inline bool invalid_probe_range(u64 va= ddr) } #endif =20 -bool probe_kernel_read_allowed(void *dst, const void *unsafe_src, size_t= size, - bool strict) +bool probe_kernel_read_allowed(void *dst, const void *unsafe_src, size_t= size) { - if (!strict) - return true; return !invalid_probe_range((unsigned long)unsafe_src); } diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h index 09d6e358883cc..99e2c2a41164a 100644 --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -301,11 +301,9 @@ copy_struct_from_user(void *dst, size_t ksize, const= void __user *src, return 0; } =20 -bool probe_kernel_read_allowed(void *dst, const void *unsafe_src, - size_t size, bool strict); +bool probe_kernel_read_allowed(void *dst, const void *unsafe_src, size_t= size); =20 extern long probe_kernel_read(void *dst, const void *src, size_t size); -extern long probe_kernel_read_strict(void *dst, const void *src, size_t = size); extern long probe_user_read(void *dst, const void __user *src, size_t si= ze); =20 extern long notrace probe_kernel_write(void *dst, const void *src, size_= t size); diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index ffe841433caa1..f694befe8ec9b 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -183,12 +183,20 @@ bpf_probe_read_kernel_common(void *dst, u32 size, c= onst void *unsafe_ptr, int ret =3D security_locked_down(LOCKDOWN_BPF_READ); =20 if (unlikely(ret < 0)) - goto out; - ret =3D compat ? probe_kernel_read(dst, unsafe_ptr, size) : - probe_kernel_read_strict(dst, unsafe_ptr, size); - if (unlikely(ret < 0)) -out: - memset(dst, 0, size); + goto fail; + + ret =3D probe_kernel_read(dst, unsafe_ptr, size); + if (unlikely(ret < 0)) { + if (compat) + ret =3D probe_user_read(dst, + (__force const void __user *)unsafe_ptr, size); + if (unlikely(ret < 0)) + goto fail; + } + + return 0; +fail: + memset(dst, 0, size); return ret; } =20 diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index 525d12137325c..1300c9fd5c755 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -1203,6 +1203,9 @@ fetch_store_strlen(unsigned long addr) =20 do { ret =3D probe_kernel_read(&c, (u8 *)addr + len, 1); + if (ret) + ret =3D probe_user_read(&c, + (__force u8 __user *)addr + len, 1); len++; } while (c && ret =3D=3D 0 && len < MAX_STRING_SIZE); =20 @@ -1275,7 +1278,13 @@ fetch_store_string_user(unsigned long addr, void *= dest, void *base) static nokprobe_inline int probe_mem_read(void *dest, void *src, size_t size) { - return probe_kernel_read(dest, src, size); + int ret; + + ret =3D probe_kernel_read(dest, src, size); + if (ret) + ret =3D probe_user_read(dest, (__force const void __user *)src, + size); + return ret; } =20 static nokprobe_inline int diff --git a/mm/maccess.c b/mm/maccess.c index cbd9d668aa46e..811f49e8de113 100644 --- a/mm/maccess.c +++ b/mm/maccess.c @@ -6,36 +6,14 @@ #include #include =20 -static long __probe_kernel_read(void *dst, const void *src, size_t size, - bool strict); - bool __weak probe_kernel_read_allowed(void *dst, const void *unsafe_src, - size_t size, bool strict) + size_t size) { return true; } =20 /** - * probe_kernel_read(): safely attempt to read from any location - * @dst: pointer to the buffer that shall take the data - * @src: address to read from - * @size: size of the data chunk - * - * Same as probe_kernel_read_strict() except that for architectures with - * not fully separated user and kernel address spaces this function also= works - * for user address tanges. - * - * DO NOT USE THIS FUNCTION - it is broken on architectures with entirel= y - * separate kernel and user address spaces, and also a bad idea otherwis= e. - */ -long probe_kernel_read(void *dst, const void *src, size_t size) -{ - return __probe_kernel_read(dst, src, size, false); -} -EXPORT_SYMBOL_GPL(probe_kernel_read); - -/** - * probe_kernel_read_strict(): safely attempt to read from kernel-space + * probe_kernel_read(): safely attempt to read from kernel-space * @dst: pointer to the buffer that shall take the data * @src: address to read from * @size: size of the data chunk @@ -48,18 +26,12 @@ EXPORT_SYMBOL_GPL(probe_kernel_read); * probe_kernel_read() suitable for use within regions where the caller * already holds mmap_sem, or other locks which nest inside mmap_sem. */ -long probe_kernel_read_strict(void *dst, const void *src, size_t size) -{ - return __probe_kernel_read(dst, src, size, true); -} - -static long __probe_kernel_read(void *dst, const void *src, size_t size, - bool strict) +long probe_kernel_read(void *dst, const void *src, size_t size) { long ret; mm_segment_t old_fs =3D get_fs(); =20 - if (!probe_kernel_read_allowed(dst, src, size, strict)) + if (!probe_kernel_read_allowed(dst, src, size)) return -EFAULT; =20 set_fs(KERNEL_DS); @@ -73,6 +45,7 @@ static long __probe_kernel_read(void *dst, const void *= src, size_t size, return -EFAULT; return 0; } +EXPORT_SYMBOL_GPL(probe_kernel_read); =20 /** * probe_user_read(): safely attempt to read from a user-space location @@ -180,7 +153,7 @@ long strncpy_from_kernel_unsafe(char *dst, const void= *unsafe_addr, long count) =20 if (unlikely(count <=3D 0)) return 0; - if (!probe_kernel_read_allowed(dst, unsafe_addr, count, true)) + if (!probe_kernel_read_allowed(dst, unsafe_addr, count)) return -EFAULT; =20 set_fs(KERNEL_DS); --=20 2.26.2