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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 07D8BC433E1 for ; Fri, 22 May 2020 00:05:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D8ACD20823 for ; Fri, 22 May 2020 00:04:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590105899; bh=nOzaaU4D0Dp728Lmp1J3pE4tiMfeddkJwOIqDp8fw7U=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=MPWOBOHxcPIOdEtsKpInI2vyTo8TwxE1bHMxaLo5F7Z3MZzfeOobyKou76zSxwBa7 M4tMiFHjdBlIEtweFgIDTr973S7CPLuQP3u9AlZ7/Ul6lYLmyN6phoBpBbDxBn87Li FWhCX8EDAol8VaRxS4aWxdEOYac5e3pdwjSDfzP0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730497AbgEVAE7 (ORCPT ); Thu, 21 May 2020 20:04:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:54794 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729771AbgEVAE6 (ORCPT ); Thu, 21 May 2020 20:04:58 -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 234A2207D8; Fri, 22 May 2020 00:04:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590105898; bh=nOzaaU4D0Dp728Lmp1J3pE4tiMfeddkJwOIqDp8fw7U=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=KYkzfNVImZyFXO92ouqtFx4Wn+lahd/EenyTm9IWrUgKxLXTM7Mw4AaNfwE/cITko b+YC+mO7bXcilZnM+LaBWxom42ehoARofe5HFRsG96aBSpHIaegnxQtnKfkOS3J+AO Om4qy3Ilig1AZ97xiA9G4WIpQ+CrYDAPjondB7YM= Date: Fri, 22 May 2020 09:04:50 +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 14/23] tracing/kprobes: handle mixed kernel/userspace probes better Message-Id: <20200522090450.a6ef7a53878c61d10340949a@kernel.org> In-Reply-To: <20200521152301.2587579-15-hch@lst.de> References: <20200521152301.2587579-1-hch@lst.de> <20200521152301.2587579-15-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=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 21 May 2020 17:22:52 +0200 Christoph Hellwig wrote: > Instead of using the dangerous probe_kernel_read and strncpy_from_unsafe > helpers, rework probes to try a user probe based on the address if the > architecture has a common address space for kernel and userspace. > This looks good to me. Acked-by: Masami Hiramatsu Thank you! > Signed-off-by: Christoph Hellwig > --- > kernel/trace/trace_kprobe.c | 72 ++++++++++++++++++++++--------------- > 1 file changed, 43 insertions(+), 29 deletions(-) > > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c > index 4325f9e7fadaa..4aeaef53ba970 100644 > --- a/kernel/trace/trace_kprobe.c > +++ b/kernel/trace/trace_kprobe.c > @@ -1200,6 +1200,15 @@ static const struct file_operations kprobe_profile_ops = { > > /* Kprobe specific fetch functions */ > > +/* Return the length of string -- including null terminal byte */ > +static nokprobe_inline int > +fetch_store_strlen_user(unsigned long addr) > +{ > + const void __user *uaddr = (__force const void __user *)addr; > + > + return strnlen_user_nofault(uaddr, MAX_STRING_SIZE); > +} > + > /* Return the length of string -- including null terminal byte */ > static nokprobe_inline int > fetch_store_strlen(unsigned long addr) > @@ -1207,30 +1216,27 @@ fetch_store_strlen(unsigned long addr) > int ret, len = 0; > u8 c; > > +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE > + if (addr < TASK_SIZE) > + return fetch_store_strlen_user(addr); > +#endif > + > do { > - ret = probe_kernel_read(&c, (u8 *)addr + len, 1); > + ret = probe_kernel_read_strict(&c, (u8 *)addr + len, 1); > len++; > } while (c && ret == 0 && len < MAX_STRING_SIZE); > > return (ret < 0) ? ret : len; > } > > -/* Return the length of string -- including null terminal byte */ > -static nokprobe_inline int > -fetch_store_strlen_user(unsigned long addr) > -{ > - const void __user *uaddr = (__force const void __user *)addr; > - > - return strnlen_user_nofault(uaddr, MAX_STRING_SIZE); > -} > - > /* > - * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max > - * length and relative data location. > + * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf > + * with max length and relative data location. > */ > static nokprobe_inline int > -fetch_store_string(unsigned long addr, void *dest, void *base) > +fetch_store_string_user(unsigned long addr, void *dest, void *base) > { > + const void __user *uaddr = (__force const void __user *)addr; > int maxlen = get_loc_len(*(u32 *)dest); > void *__dest; > long ret; > @@ -1240,11 +1246,7 @@ fetch_store_string(unsigned long addr, void *dest, void *base) > > __dest = get_loc_data(dest, base); > > - /* > - * Try to get string again, since the string can be changed while > - * probing. > - */ > - ret = strncpy_from_unsafe(__dest, (void *)addr, maxlen); > + ret = strncpy_from_user_nofault(__dest, uaddr, maxlen); > if (ret >= 0) > *(u32 *)dest = make_data_loc(ret, __dest - base); > > @@ -1252,35 +1254,37 @@ fetch_store_string(unsigned long addr, void *dest, void *base) > } > > /* > - * Fetch a null-terminated string from user. Caller MUST set *(u32 *)buf > - * with max length and relative data location. > + * Fetch a null-terminated string. Caller MUST set *(u32 *)buf with max > + * length and relative data location. > */ > static nokprobe_inline int > -fetch_store_string_user(unsigned long addr, void *dest, void *base) > +fetch_store_string(unsigned long addr, void *dest, void *base) > { > - const void __user *uaddr = (__force const void __user *)addr; > int maxlen = get_loc_len(*(u32 *)dest); > void *__dest; > long ret; > > +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE > + if ((unsigned long)addr < TASK_SIZE) > + return fetch_store_string_user(addr, dest, base); > +#endif > + > if (unlikely(!maxlen)) > return -ENOMEM; > > __dest = get_loc_data(dest, base); > > - ret = strncpy_from_user_nofault(__dest, uaddr, maxlen); > + /* > + * Try to get string again, since the string can be changed while > + * probing. > + */ > + ret = strncpy_from_user_nofault(__dest, (void *)addr, maxlen); > if (ret >= 0) > *(u32 *)dest = make_data_loc(ret, __dest - base); > > return ret; > } > > -static nokprobe_inline int > -probe_mem_read(void *dest, void *src, size_t size) > -{ > - return probe_kernel_read(dest, src, size); > -} > - > static nokprobe_inline int > probe_mem_read_user(void *dest, void *src, size_t size) > { > @@ -1289,6 +1293,16 @@ probe_mem_read_user(void *dest, void *src, size_t size) > return probe_user_read(dest, uaddr, size); > } > > +static nokprobe_inline int > +probe_mem_read(void *dest, void *src, size_t size) > +{ > +#ifdef CONFIG_ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE > + if ((unsigned long)src < TASK_SIZE) > + return probe_mem_read_user(dest, src, size); > +#endif > + return probe_kernel_read_strict(dest, src, size); > +} > + > /* Note that we don't verify it, since the code does not come from user space */ > static int > process_fetch_insn(struct fetch_insn *code, struct pt_regs *regs, void *dest, > -- > 2.26.2 > -- Masami Hiramatsu