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=unavailable 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 B829AC433E0 for ; Wed, 13 May 2020 16:16:26 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id C695D2053B for ; Wed, 13 May 2020 16:16:26 +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="FVfJfA1I" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C695D2053B 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 168EE8001C; Wed, 13 May 2020 12:16:26 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 11A308000B; Wed, 13 May 2020 12:16:26 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 030238001C; Wed, 13 May 2020 12:16:25 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0219.hostedemail.com [216.40.44.219]) by kanga.kvack.org (Postfix) with ESMTP id DA04A8000B for ; Wed, 13 May 2020 12:16:25 -0400 (EDT) Received: from smtpin01.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 989B6181AC9B6 for ; Wed, 13 May 2020 16:16:25 +0000 (UTC) X-FDA: 76812198330.01.knife94_5528bda2fbd00 X-HE-Tag: knife94_5528bda2fbd00 X-Filterd-Recvd-Size: 9776 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) by imf27.hostedemail.com (Postfix) with ESMTP for ; Wed, 13 May 2020 16:16:25 +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=vP/pOG7kUTf44WhDvEFmnpEwW5+r2wsdj7OXFXYA+Ew=; b=FVfJfA1IdHzbtC8oKrBYaKVZWw RK0y2czeUJvDrqtVfMxpWc+hr+wNwMZRUNeTOc8OoQFhTiQN4yTLKgP0Jve6YYJns0tYckJGcszTF U01o9+jzL8rjOB2IaSNoTsccru8tYSL0Jtqkbp9mlV4zycUlrwiNiz/NjQjiPPZIgYmq61okOle7V 6trdXYj+5znBLdykpRTZijlC3U2PL40z1tSwQwbRsO7yBEriCsrQxiAoS9AwPbnL/AjQ+yooenlvF pTOe0XKuan1nxaq0nfat1o+iWhB4bsn1eeNEDC7ZXvGJuMyoXQJg+B3uW0k+O/Ns/CtIcRtR+2MWx D+F7FA4w==; Received: from [2001:4bb8:180:9d3f:c70:4a89:bc61:2] (helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jYtom-0004wG-9E; Wed, 13 May 2020 16:01:12 +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 12/18] maccess: always use strict semantics for probe_kernel_read Date: Wed, 13 May 2020 18:00:32 +0200 Message-Id: <20200513160038.2482415-13-hch@lst.de> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200513160038.2482415-1-hch@lst.de> References: <20200513160038.2482415-1-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 Reviewed-by: Masami Hiramatsu --- 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 28944a14e0534..78e0ff8641559 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 0d849acc9de38..5dea4169a8323 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -180,15 +180,23 @@ static __always_inline int bpf_probe_read_kernel_common(void *dst, u32 size, const void *unsafe_ptr= , const bool compat) { + const void __user *user_ptr =3D (__force const void __user *)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, user_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 8c456e30933d3..7725146369731 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -1209,6 +1209,9 @@ 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 @@ -1281,7 +1284,13 @@ 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); + const void __user *user_ptr =3D (__force const void __user *)src; + int ret; + + ret =3D probe_kernel_read(dest, src, size); + if (ret) + ret =3D probe_user_read(dest, user_ptr, size); + return ret; } =20 static nokprobe_inline int diff --git a/mm/maccess.c b/mm/maccess.c index 3d85e48013e6b..05c44d490b4e3 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_nofault(char *dst, const voi= d *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