From patchwork Tue Nov 7 05:40:56 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Masahisa Kojima X-Patchwork-Id: 742405 Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E648D20E7 for ; Tue, 7 Nov 2023 05:43:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="AX+8NgmU" 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 D3F3118F for ; Mon, 6 Nov 2023 21:43:26 -0800 (PST) Received: by mail-pl1-x632.google.com with SMTP id d9443c01a7336-1cc3542e328so36063195ad.1 for ; Mon, 06 Nov 2023 21:43:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1699335806; x=1699940606; 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=LjE6MRKZln7VtAWqDMH/BbdtqTCVNkHO+jOGQ3GR3ng=; b=AX+8NgmU7EGW2biZfrlJxeZp8VMxDKSeGVbWLHTYnTnM1b6ZtQE93s5J1qj3PLOgqB areCL5KyCLbo9h8ZKMhp+LdXPNhCCzY5b3k5nBbo19a32td8X8qfi4XnRMvqR4zXTlOA fHHbgyJoS6MRTD5HEJUXXyDWvu/7XcREV5iPy1YAyuqRmJOlGu3QGxRaTQklwfzTNZ5x 3EEza5TZwOv3R5T8jNG3ide1/X5V1X0neOE4q1cxK/OkR9zdTTMHUiS48uxzrLwVRtu7 /afV0RRejtTTY0CJaH7YG4ZNJXijKyVL7w5RQWD4UPLvX4cyqogvu0YwNCsnJYc7vE06 JG3w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1699335806; x=1699940606; 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=LjE6MRKZln7VtAWqDMH/BbdtqTCVNkHO+jOGQ3GR3ng=; b=LPon5kt468ETDy+rbr56c84rTO0QZxEshRYb++qWesK+xRwxs5BWIbtz0AaMQXMHhH QSSVnsjQ27aC4kNJ46zBqP9XreZbd+AAT6q/5R7rq1sQcZq9NGljjKOoyeL3QhRfsluu 1kt49IQrGym4PJzDG3I7HCixcrw7fqoar2b0YwF/WJoS7jMW9weChJ1bsXc5w658oVrx 55o4ja6SQu+m9eu8fp8n71g69ZA6L/pvKYQLoE1Ru1fX7P0pWZ+kY2CFI50YUo/eHF7f 0m7GzlCd6GNGU23da5pVQz3pUBWH+CKElS17g4svIoxf+72xWLHoroBFrpvyAhSZtn2K DyQQ== X-Gm-Message-State: AOJu0Yw2ZBR1YVwlGzlrgYUpnDo+Sx0ly/7CM4gLclTWC9t8+ff6eJ7/ kWHTZuW9sThG9Q5Y4auedP0Eow== X-Google-Smtp-Source: AGHT+IH+Gm91nZYVteceVDahZxIliP0ESJuCzAMIRZ4I3uVN7mWTtDK4uUS3eOsCi7L5bJHUkClfBA== X-Received: by 2002:a17:902:d50d:b0:1cc:3875:e654 with SMTP id b13-20020a170902d50d00b001cc3875e654mr24828909plg.26.1699335806334; Mon, 06 Nov 2023 21:43:26 -0800 (PST) Received: from localhost.localdomain (fp9875a45d.knge128.ap.nuro.jp. [152.117.164.93]) by smtp.gmail.com with ESMTPSA id b17-20020a170902ed1100b001cc530c495asm6752053pld.113.2023.11.06.21.43.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Nov 2023 21:43:25 -0800 (PST) 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 v10 5/5] efivarfs: force RO when remounting if SetVariable is not supported Date: Tue, 7 Nov 2023 14:40:56 +0900 Message-Id: <20231107054057.1893-6-masahisa.kojima@linaro.org> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20231107054057.1893-1-masahisa.kojima@linaro.org> References: <20231107054057.1893-1-masahisa.kojima@linaro.org> Precedence: bulk X-Mailing-List: linux-efi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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 5751413d124c..2b71e5106d13 100644 --- a/fs/efivarfs/super.c +++ b/fs/efivarfs/super.c @@ -16,6 +16,7 @@ #include #include #include +#include #include "internal.h" @@ -356,9 +357,20 @@ 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, .parse_param = efivarfs_parse_param, + .reconfigure = efivarfs_reconfigure, }; static int efivarfs_init_fs_context(struct fs_context *fc)