From patchwork Thu May 21 15:22:56 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 1295278 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=none (no SPF record) smtp.mailfrom=lists.infradead.org (client-ip=2607:7c80:54:e::133; helo=bombadil.infradead.org; envelope-from=linux-um-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org; receiver=) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20170209 header.b=T1llc+4z; dkim-atps=neutral Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 49SYLX69SLz9sSt for ; Fri, 22 May 2020 01:24:04 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=6i4P9DtKdZLRo+h7smOhDmsB9/RwaamIdoZQsgSsVfQ=; b=T1llc+4ztEn+jl +1pc7KG0XOt/O5k4KwIdQULwh/dPtUlcUNb+egvOo13eV9kn08pHb48RWqfkBad+xhuV0o78BHyGQ +MCOHaYkF8nrrI6p/4sAdGb9t17m359lBZqSnv4Ge5ql0wRwsCn742HqGHtK5F/29AEvFFxqE9RzS W4D98yPN4m6Uc+3K+yKDLnN5ydAGqYBhYeK/DIq+LutbGvLZ46fc8+OVBeMWv79C0P6wteFiW7DML at/o/DIIwVtq++GB/6zZDGL+VAFgZ0y/DU+gwF3Sq3XM87pzaAa7jCwJIqksDIvNk/CDasykxAwB5 0nZqBFTUDdVUmKKMEz8Q==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jbn38-0004fo-Fb; Thu, 21 May 2020 15:23:58 +0000 Received: from [2001:4bb8:18c:5da7:c70:4a89:bc61:2] (helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1jbn37-0004dA-3G; Thu, 21 May 2020 15:23:57 +0000 From: Christoph Hellwig To: x86@kernel.org, Alexei Starovoitov , Daniel Borkmann , Masami Hiramatsu , Linus Torvalds , Andrew Morton Subject: [PATCH 18/23] maccess: allow architectures to provide kernel probing directly Date: Thu, 21 May 2020 17:22:56 +0200 Message-Id: <20200521152301.2587579-19-hch@lst.de> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200521152301.2587579-1-hch@lst.de> References: <20200521152301.2587579-1-hch@lst.de> MIME-Version: 1.0 X-BeenThere: linux-um@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-parisc@vger.kernel.org, netdev@vger.kernel.org, linux-um@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org Sender: "linux-um" Errors-To: linux-um-bounces+incoming=patchwork.ozlabs.org@lists.infradead.org Provide alternative versions of probe_kernel_read, probe_kernel_write and strncpy_from_kernel_unsafe that don't need set_fs magic, but instead use arch hooks that are modelled after unsafe_{get,put}_user to access kernel memory in an exception safe way. Signed-off-by: Christoph Hellwig --- mm/maccess.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 76 insertions(+) diff --git a/mm/maccess.c b/mm/maccess.c index ffde1ae86ec51..e19d19cd5382c 100644 --- a/mm/maccess.c +++ b/mm/maccess.c @@ -11,6 +11,81 @@ bool __weak probe_kernel_read_allowed(const void *unsafe_src, size_t size) return true; } +#ifdef HAVE_GET_KERNEL_NOFAULT + +#define probe_kernel_read_loop(dst, src, len, type, err_label) \ + while (len >= sizeof(type)) { \ + __get_kernel_nofault(dst, src, type, err_label); \ + dst += sizeof(type); \ + src += sizeof(type); \ + len -= sizeof(type); \ + } + +long probe_kernel_read(void *dst, const void *src, size_t size) +{ + if (!probe_kernel_read_allowed(src, size)) + return -EFAULT; + + pagefault_disable(); + probe_kernel_read_loop(dst, src, size, u64, Efault); + probe_kernel_read_loop(dst, src, size, u32, Efault); + probe_kernel_read_loop(dst, src, size, u16, Efault); + probe_kernel_read_loop(dst, src, size, u8, Efault); + pagefault_enable(); + return 0; +Efault: + pagefault_enable(); + return -EFAULT; +} +EXPORT_SYMBOL_GPL(probe_kernel_read); + +#define probe_kernel_write_loop(dst, src, len, type, err_label) \ + while (len >= sizeof(type)) { \ + __put_kernel_nofault(dst, src, type, err_label); \ + dst += sizeof(type); \ + src += sizeof(type); \ + len -= sizeof(type); \ + } + +long probe_kernel_write(void *dst, const void *src, size_t size) +{ + pagefault_disable(); + probe_kernel_write_loop(dst, src, size, u64, Efault); + probe_kernel_write_loop(dst, src, size, u32, Efault); + probe_kernel_write_loop(dst, src, size, u16, Efault); + probe_kernel_write_loop(dst, src, size, u8, Efault); + pagefault_enable(); + return 0; +Efault: + pagefault_enable(); + return -EFAULT; +} + +long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count) +{ + const void *src = unsafe_addr; + + if (unlikely(count <= 0)) + return 0; + if (!probe_kernel_read_allowed(unsafe_addr, count)) + return -EFAULT; + + pagefault_disable(); + do { + __get_kernel_nofault(dst, src, u8, Efault); + dst++; + src++; + } while (dst[-1] && src - unsafe_addr < count); + pagefault_enable(); + + dst[-1] = '\0'; + return src - unsafe_addr; +Efault: + pagefault_enable(); + dst[-1] = '\0'; + return -EFAULT; +} +#else /* HAVE_GET_KERNEL_NOFAULT */ /** * probe_kernel_read(): safely attempt to read from kernel-space * @dst: pointer to the buffer that shall take the data @@ -113,6 +188,7 @@ long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count) return ret ? -EFAULT : src - unsafe_addr; } +#endif /* HAVE_GET_KERNEL_NOFAULT */ /** * probe_user_read(): safely attempt to read from a user-space location