From patchwork Fri Oct 13 07:45:38 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Masahisa Kojima X-Patchwork-Id: 733482 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 B22E3CDB47E for ; Fri, 13 Oct 2023 07:48:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230011AbjJMHsE (ORCPT ); Fri, 13 Oct 2023 03:48:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42388 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230012AbjJMHrz (ORCPT ); Fri, 13 Oct 2023 03:47:55 -0400 Received: from mail-pl1-x632.google.com (mail-pl1-x632.google.com [IPv6:2607:f8b0:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 87131ED for ; Fri, 13 Oct 2023 00:47:45 -0700 (PDT) Received: by mail-pl1-x632.google.com with SMTP id d9443c01a7336-1c5c91bec75so14124485ad.3 for ; Fri, 13 Oct 2023 00:47:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1697183265; x=1697788065; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=8akGMHqFqX7T+gUZEmXOvoAIZo+dmI+wsqgaBTkWBZQ=; b=VTgMJS+K820c7C5vG0MSEo0C/n9nCvVyenXhzuPF1RAh701Dns8sU4iswXj24lByaz y5CwZ2dZHpI0NMEeX4B7j/GUUhGbl5j5jzfHVsGfnpYekk/QJhpQ53rt51vnNiTmq9vP 7ob99PWPZsG5mywG9GDAewUNlCLwddaIg9HpDyIxo791J025GLv0eorNgs1r7HbRsWe6 viq9LB9Z7ylJIwvk/FSCugcTOOW+D7OAhWVv36OCMuSDttksQ/p8aOT8d8WfqrzZT2X6 toF7GvSiKPEwfnafNONAXcyeWcMcOczd4xUkd3LFNkNqfCClVPdLiQQpYkYCBu9b8Wuh MIXQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1697183265; x=1697788065; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=8akGMHqFqX7T+gUZEmXOvoAIZo+dmI+wsqgaBTkWBZQ=; b=X2AdjphaiJaNK23oxi720I2V2vtYmTJZ3csEx6RNWrLsmLwsiwT7bsHD3AgFcYm+if dbIBhB/0JNb6hWjEM0fKw6qBdgMmgvrV6dfxU6BIfgm88Tc+Vcetn/9+Im/m1aaRIYxm ueLWUJYrpmTvcTdfdXp+b6ABvV6dcsF6WSOMfupR0r8E1++7cI2rjCfGhB/ivYiwdLC0 j4rIBAZCz5r/VBElR33G6u9oGoWw5DaA7sNO1/f6Ebs6DVchFBU+AYJd9WzMlqQ3kgKD jOfFPKmQjGvfbW4SNJbazMuudIcxQ8DlWHhhZL9AdxPFE89DWB+Vi2tnLYA6veALCvP0 wiNQ== X-Gm-Message-State: AOJu0Yw9OZchAa1RA9bmRlnSi8cfhvmBpmGc9kK+Hz/tuqAgcHqXMVfe BrCE5l1Zh91rXSPtn4QDWtnyWA== X-Google-Smtp-Source: AGHT+IGVP0Ap9uRXWpHCPazerzjjrIqxMfkxGsyo0HNCkfR4Q/WjC4suytJRQkb6ZV8mzfi51taqVQ== X-Received: by 2002:a17:902:d485:b0:1c8:791c:d782 with SMTP id c5-20020a170902d48500b001c8791cd782mr26950813plg.29.1697183264817; Fri, 13 Oct 2023 00:47:44 -0700 (PDT) Received: from localhost.localdomain (fp9875a45d.knge128.ap.nuro.jp. [152.117.164.93]) by smtp.gmail.com with ESMTPSA id z8-20020a170903018800b001c9ccbb8fdasm3200548plg.260.2023.10.13.00.47.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Oct 2023 00:47:44 -0700 (PDT) From: Masahisa Kojima To: Ard Biesheuvel , Jens Wiklander , Jan Kiszka , Sumit Garg , linux-kernel@vger.kernel.org, op-tee@lists.trustedfirmware.org Cc: Ilias Apalodimas , Johan Hovold , Masahisa Kojima , Randy Dunlap , Heinrich Schuchardt , Jonathan Cameron , Jeremy Kerr , linux-efi@vger.kernel.org Subject: [PATCH v9 5/6] efivarfs: force RO when remounting if SetVariable is not supported Date: Fri, 13 Oct 2023 16:45:38 +0900 Message-Id: <20231013074540.8980-6-masahisa.kojima@linaro.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20231013074540.8980-1-masahisa.kojima@linaro.org> References: <20231013074540.8980-1-masahisa.kojima@linaro.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org From: Ilias Apalodimas If SetVariable at runtime is not supported by the firmware we never assign a callback for that function. At the same time mount the efivarfs as RO so no one can call that. However, we never check the permission flags when someone remounts the filesystem as RW. As a result this leads to a crash looking like this: $ mount -o remount,rw /sys/firmware/efi/efivars $ efi-updatevar -f PK.auth PK [ 303.279166] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 [ 303.280482] Mem abort info: [ 303.280854] ESR = 0x0000000086000004 [ 303.281338] EC = 0x21: IABT (current EL), IL = 32 bits [ 303.282016] SET = 0, FnV = 0 [ 303.282414] EA = 0, S1PTW = 0 [ 303.282821] FSC = 0x04: level 0 translation fault [ 303.283771] user pgtable: 4k pages, 48-bit VAs, pgdp=000000004258c000 [ 303.284913] [0000000000000000] pgd=0000000000000000, p4d=0000000000000000 [ 303.286076] Internal error: Oops: 0000000086000004 [#1] PREEMPT SMP [ 303.286936] Modules linked in: qrtr tpm_tis tpm_tis_core crct10dif_ce arm_smccc_trng rng_core drm fuse ip_tables x_tables ipv6 [ 303.288586] CPU: 1 PID: 755 Comm: efi-updatevar Not tainted 6.3.0-rc1-00108-gc7d0c4695c68 #1 [ 303.289748] Hardware name: Unknown Unknown Product/Unknown Product, BIOS 2023.04-00627-g88336918701d 04/01/2023 [ 303.291150] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 303.292123] pc : 0x0 [ 303.292443] lr : efivar_set_variable_locked+0x74/0xec [ 303.293156] sp : ffff800008673c10 [ 303.293619] x29: ffff800008673c10 x28: ffff0000037e8000 x27: 0000000000000000 [ 303.294592] x26: 0000000000000800 x25: ffff000002467400 x24: 0000000000000027 [ 303.295572] x23: ffffd49ea9832000 x22: ffff0000020c9800 x21: ffff000002467000 [ 303.296566] x20: 0000000000000001 x19: 00000000000007fc x18: 0000000000000000 [ 303.297531] x17: 0000000000000000 x16: 0000000000000000 x15: 0000aaaac807ab54 [ 303.298495] x14: ed37489f673633c0 x13: 71c45c606de13f80 x12: 47464259e219acf4 [ 303.299453] x11: ffff000002af7b01 x10: 0000000000000003 x9 : 0000000000000002 [ 303.300431] x8 : 0000000000000010 x7 : ffffd49ea8973230 x6 : 0000000000a85201 [ 303.301412] x5 : 0000000000000000 x4 : ffff0000020c9800 x3 : 00000000000007fc [ 303.302370] x2 : 0000000000000027 x1 : ffff000002467400 x0 : ffff000002467000 [ 303.303341] Call trace: [ 303.303679] 0x0 [ 303.303938] efivar_entry_set_get_size+0x98/0x16c [ 303.304585] efivarfs_file_write+0xd0/0x1a4 [ 303.305148] vfs_write+0xc4/0x2e4 [ 303.305601] ksys_write+0x70/0x104 [ 303.306073] __arm64_sys_write+0x1c/0x28 [ 303.306622] invoke_syscall+0x48/0x114 [ 303.307156] el0_svc_common.constprop.0+0x44/0xec [ 303.307803] do_el0_svc+0x38/0x98 [ 303.308268] el0_svc+0x2c/0x84 [ 303.308702] el0t_64_sync_handler+0xf4/0x120 [ 303.309293] el0t_64_sync+0x190/0x194 [ 303.309794] Code: ???????? ???????? ???????? ???????? (????????) [ 303.310612] ---[ end trace 0000000000000000 ]--- Fix this by adding a .reconfigure() function to the fs operations which we can use to check the requested flags and deny anything that's not RO if the firmware doesn't implement SetVariable at runtime. Fixes: f88814cc2578 ("efi/efivars: Expose RT service availability via efivars abstraction") Signed-off-by: Ilias Apalodimas --- fs/efivarfs/super.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/fs/efivarfs/super.c b/fs/efivarfs/super.c index 0f6e4d223aea..942e748a4e03 100644 --- a/fs/efivarfs/super.c +++ b/fs/efivarfs/super.c @@ -15,6 +15,7 @@ #include #include #include +#include #include "internal.h" @@ -300,8 +301,19 @@ static int efivarfs_get_tree(struct fs_context *fc) return get_tree_single(fc, efivarfs_fill_super); } +static int efivarfs_reconfigure(struct fs_context *fc) +{ + if (!efivar_supports_writes() && !(fc->sb_flags & SB_RDONLY)) { + pr_err("Firmware does not support SetVariableRT. Can not remount with rw\n"); + return -EINVAL; + } + + return 0; +} + static const struct fs_context_operations efivarfs_context_ops = { .get_tree = efivarfs_get_tree, + .reconfigure = efivarfs_reconfigure, }; static int efivarfs_init_fs_context(struct fs_context *fc)