From patchwork Tue Aug 1 20:43:07 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nathan Lynch via B4 Relay X-Patchwork-Id: 13337239 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8E69FC0015E for ; Tue, 1 Aug 2023 20:43:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231769AbjHAUnO (ORCPT ); Tue, 1 Aug 2023 16:43:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55652 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229669AbjHAUnN (ORCPT ); Tue, 1 Aug 2023 16:43:13 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D784B1722; Tue, 1 Aug 2023 13:43:12 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 73AFC616EA; Tue, 1 Aug 2023 20:43:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPS id D34EBC433C8; Tue, 1 Aug 2023 20:43:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1690922591; bh=C0I3Ru7GOW95oqbdSWRCdIV1RALO1IK4Jpy3kgeDRGU=; h=From:Date:Subject:To:Cc:Reply-To:From; b=Lqve3I6cH3czggt0HoV5slmlN4T4zTo9Icns7Xl/n5Hf0BwWRBmKUmXc8IrXuMTmJ iC3WgV92E70Va2qNju4RBhgduQRPFIT5DKTkV/ykL8MEa9v/copUXYI07zn9MvvnoD SBgBNeGcIBa/P9MPU96pgWOzyn9aC6E8lhqWLv54VtW7n1xbAnu9EqS0JBngXM9onB Ix4FsYogjfmgVbHi98Thcjwa6cOT8xzgwnG5JiSowJV0dqAwP+iSguj39MHQpj+nnm CrpZ1CQS90MM06x9SeJzYSiYb+YnAhPZvAs8SJKIphA+2u2l7KHg8+2hk0YCMJ5WiW Sla5mU9sJyQfQ== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id BAB58C0015E; Tue, 1 Aug 2023 20:43:11 +0000 (UTC) From: Nathan Lynch via B4 Relay Date: Tue, 01 Aug 2023 15:43:07 -0500 Subject: [PATCH] powerpc/rtas_flash: allow user copy to flash block cache objects MIME-Version: 1.0 Message-Id: <20230801-rtas-flash-vs-hardened-usercopy-v1-1-2e99cf9e2bed@linux.ibm.com> X-B4-Tracking: v=1; b=H4sIAFpuyWQC/x3NTQqDQAxA4atI1g3MD1jaqxQX0YmdQBklsaKId 3dw+TbfO8BYhQ3ezQHKq5hMpYZ/NDBkKl9GSbUhuBDdM3rUhQzHH1nG1TCTJi6c8F+dYZp3dC9 qU4ht77yHqszKo2z34dOd5wWga1b/cQAAAA== To: Michael Ellerman , Nicholas Piggin , Christophe Leroy , Kees Cook Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Nathan Lynch X-Mailer: b4 0.12.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1690922591; l=3523; i=nathanl@linux.ibm.com; s=20230206; h=from:subject:message-id; bh=7SUjRaAqad/a9pJchkB3VHzS+si/gdmTstqU0MaHrlA=; b=u2yXJ1USIHBZnDyFxJ/BYcgYZAEArFBRYWN27AoxZ2K5TbQo/YNf74+f1y6Tez0VodPXdoRKj fIJeLfXp44uAkqunq4GulH6Q0kEhdoRZn6sszqffJyKSH/FUInksig5 X-Developer-Key: i=nathanl@linux.ibm.com; a=ed25519; pk=6daubz/ymoaMF+8voz7UHwnhluEsmDZuqygIIMWpQQY= X-Endpoint-Received: by B4 Relay for nathanl@linux.ibm.com/20230206 with auth_id=27 X-Original-From: Nathan Lynch Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org From: Nathan Lynch With hardened usercopy enabled (CONFIG_HARDENED_USERCOPY=y), using the /proc/powerpc/rtas/firmware_update interface to prepare a system firmware update yields a BUG(): kernel BUG at mm/usercopy.c:102! Oops: Exception in kernel mode, sig: 5 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries Modules linked in: CPU: 0 PID: 2232 Comm: dd Not tainted 6.5.0-rc3+ #2 Hardware name: IBM,8408-E8E POWER8E (raw) 0x4b0201 0xf000004 of:IBM,FW860.50 (SV860_146) hv:phyp pSeries NIP: c0000000005991d0 LR: c0000000005991cc CTR: 0000000000000000 REGS: c0000000148c76a0 TRAP: 0700 Not tainted (6.5.0-rc3+) MSR: 8000000000029033 CR: 24002242 XER: 0000000c CFAR: c0000000001fbd34 IRQMASK: 0 [ ... GPRs omitted ... ] NIP [c0000000005991d0] usercopy_abort+0xa0/0xb0 LR [c0000000005991cc] usercopy_abort+0x9c/0xb0 Call Trace: [c0000000148c7940] [c0000000005991cc] usercopy_abort+0x9c/0xb0 (unreliable) [c0000000148c79b0] [c000000000536814] __check_heap_object+0x1b4/0x1d0 [c0000000148c79f0] [c000000000599080] __check_object_size+0x2d0/0x380 [c0000000148c7a30] [c000000000045ed4] rtas_flash_write+0xe4/0x250 [c0000000148c7a80] [c00000000068a0fc] proc_reg_write+0xfc/0x160 [c0000000148c7ab0] [c0000000005a381c] vfs_write+0xfc/0x4e0 [c0000000148c7b70] [c0000000005a3e10] ksys_write+0x90/0x160 [c0000000148c7bc0] [c00000000002f2c8] system_call_exception+0x178/0x320 [c0000000148c7e50] [c00000000000d520] system_call_common+0x160/0x2c4 --- interrupt: c00 at 0x7fff9f17e5e4 The blocks of the firmware image are copied directly from user memory to objects allocated from flash_block_cache, so flash_block_cache must be created using kmem_cache_create_usercopy() to mark it safe for user access. Fixes: 6d07d1cd300f ("usercopy: Restrict non-usercopy caches to size 0") Signed-off-by: Nathan Lynch --- I believe it's much more common to update Power system firmware without involving a Linux partition, which may explain why this has gone unreported for so long. --- arch/powerpc/kernel/rtas_flash.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) --- base-commit: c3cad890877f59aeeaf5a638aa7a7c0612c16fa1 change-id: 20230731-rtas-flash-vs-hardened-usercopy-09a6d236b011 Best regards, diff --git a/arch/powerpc/kernel/rtas_flash.c b/arch/powerpc/kernel/rtas_flash.c index 4caf5e3079eb..6a837264a196 100644 --- a/arch/powerpc/kernel/rtas_flash.c +++ b/arch/powerpc/kernel/rtas_flash.c @@ -698,6 +698,12 @@ static const struct rtas_flash_file rtas_flash_files[] = { static int __init rtas_flash_init(void) { + const unsigned int objsize = RTAS_BLK_SIZE; + const unsigned int usersize = objsize; + const unsigned int align = objsize; + void (* const ctor)(void *) = NULL; + const unsigned int useroffset = 0; + const slab_flags_t flags = 0; int i; if (rtas_function_token(RTAS_FN_IBM_UPDATE_FLASH_64_AND_REBOOT) == RTAS_UNKNOWN_SERVICE) { @@ -709,9 +715,9 @@ static int __init rtas_flash_init(void) if (!rtas_validate_flash_data.buf) return -ENOMEM; - flash_block_cache = kmem_cache_create("rtas_flash_cache", - RTAS_BLK_SIZE, RTAS_BLK_SIZE, 0, - NULL); + flash_block_cache = kmem_cache_create_usercopy("rtas_flash_cache", + objsize, align, flags, + useroffset, usersize, ctor); if (!flash_block_cache) { printk(KERN_ERR "%s: failed to create block cache\n", __func__);