From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-243.mta1.migadu.com [95.215.58.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 19FCD1DE8BF for ; Sat, 15 Aug 2026 11:06:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.243 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786791998; cv=none; b=ssV75u0fdkxvTW2ETK8XU4aTguqYbcbKrOfscslUWbJfYWRz64YN4ABc4DsVgdZj6NRXTW1L7ihVm2LMQ5Nx223QkdUNzzkj6JMe2Y7OV+Y9G6ScXUruxUeGem1B/EhOfuOAAS4aGxqPCetHfrsT9wAuGmdFvYJcMa6VM9OfS40= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786791998; c=relaxed/simple; bh=1WdTn+7H9RJKUpvaMNGvGCbAlYyK8JOZD2Kd1+lXH2w=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=SCi37YvhHhmXYKC1WB8wgc0G7tR1outzEN1UxDcHtuSFJURHG1pWVRSmw8tgjAu+vaaUIaaAtR2pJJsrcBW7pNWtQLgOkXK6Zp0IyY/9rSd5oxoOeEuQu8vlFcMsAAugoQCZ5stbR2jhGmok6c+y8vn1NrCK33N5YPM3mxoc8zw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=OFJ9qcrn; arc=none smtp.client-ip=95.215.58.243 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="OFJ9qcrn" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=1WdTn+7H9RJKUpvaMNGvGCbAlYyK8JOZD2Kd1+lXH2w=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1786791992; v=1; x=1787396792; b=OFJ9qcrngFF0Pb+OJcBaKCrVBRPrx4E7BN+a4YqFx4N0cdI5lk0Ho1HY6OeaKCmn7Goswzgb wonbsCqViF0cvZF36s9N/46yTAfRSdXbSrgGWt0LAlvOWtaID35Nl8efxSEmQB8ZZzypXIW+5Yu uForyrFCkPxgCUP2PzAC+1WM= X-Envelope-To: linux-kernel@vger.kernel.org Received: from fedora.fritz.box (62.216.208.217) by smtp.migadu.com with ESMTPS id ca7c6818f9b6bd40; Sat, 15 Aug 2026 11:06:32 +0000 X-Migadu-Flow: FLOW_OUT From: Thorsten Blum To: Alasdair Kergon , Mike Snitzer , Mikulas Patocka , Benjamin Marzinski Cc: Thorsten Blum , dm-devel@lists.linux.dev, linux-kernel@vger.kernel.org Subject: [PATCH] dm-crypt: Use memzero_explicit() to wipe key material Date: Sat, 15 Aug 2026 13:05:33 +0200 Message-ID: <20260815110532.5343-3-thorsten.blum@linux.dev> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3206; i=thorsten.blum@linux.dev; h=from:subject; bh=1WdTn+7H9RJKUpvaMNGvGCbAlYyK8JOZD2Kd1+lXH2w=; b=owGbwMvMwCUWt7pQ4caZUj3G02pJDFkN7n8mtfWrlTpI9HMW/O175NV04EhLvX/Kp7vfJL/4i rQ86jncUcrCIMbFICumyPJg1o8ZvqU1lZtMInbCzGFlAhnCwMUpABPpPcLwP2d5R84D/YyX7+dI PN/fcj+e3V7R67pUsM3EPP97ly/f+MTwz+Kxpf3DBZ855QXyPnVuFkmeeMG8p7T/9u5Z4RanV4u s5gYA X-Developer-Key: i=thorsten.blum@linux.dev; a=openpgp; fpr=1D60735E8AEF3BE473B69D84733678FD8DFEEAD4 Content-Transfer-Encoding: 8bit The code still wipes key material with memset(). Use memzero_explicit() to prevent the compiler from optimizing these wipes away. Also use size_t for the string length passed to memzero_explicit() and drop the redundant sizeof(u8) multiplications. Signed-off-by: Thorsten Blum --- drivers/md/dm-crypt.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c index 608b617fb817..5194294871db 100644 --- a/drivers/md/dm-crypt.c +++ b/drivers/md/dm-crypt.c @@ -513,7 +513,7 @@ static void crypt_iv_lmk_wipe(struct crypt_config *cc) struct iv_lmk_private *lmk = &cc->iv_gen_private.lmk; if (lmk->seed) - memset(lmk->seed, 0, LMK_SEED_SIZE); + memzero_explicit(lmk->seed, LMK_SEED_SIZE); } static void crypt_iv_lmk_one(struct crypt_config *cc, u8 *iv, @@ -630,8 +630,8 @@ static void crypt_iv_tcw_wipe(struct crypt_config *cc) { struct iv_tcw_private *tcw = &cc->iv_gen_private.tcw; - memset(tcw->iv_seed, 0, cc->iv_size); - memset(tcw->whitening, 0, TCW_WHITENING_SIZE); + memzero_explicit(tcw->iv_seed, cc->iv_size); + memzero_explicit(tcw->whitening, TCW_WHITENING_SIZE); } static void crypt_iv_tcw_whitening(struct crypt_config *cc, @@ -2596,7 +2596,7 @@ static int get_key_size(char **key_string) static int crypt_set_key(struct crypt_config *cc, char *key) { int r = -EINVAL; - int key_string_len = strlen(key); + size_t key_string_len = strlen(key); /* Hyphen (which gives a key_size of zero) means there is no key. */ if (!cc->key_size && strcmp(key, "-")) @@ -2625,7 +2625,7 @@ static int crypt_set_key(struct crypt_config *cc, char *key) out: /* Hex key string not needed after here, so wipe it. */ - memset(key, '0', key_string_len); + memzero_explicit(key, key_string_len); return r; } @@ -2644,7 +2644,7 @@ static int crypt_wipe_key(struct crypt_config *cc) kfree_sensitive(cc->key_string); cc->key_string = NULL; r = crypt_setkey(cc); - memset(&cc->key, 0, cc->key_size * sizeof(u8)); + memzero_explicit(cc->key, cc->key_size); return r; } @@ -3065,7 +3065,7 @@ static int crypt_ctr_cipher(struct dm_target *ti, char *cipher_in, char *key) /* wipe the kernel key payload copy */ if (cc->key_string) - memset(cc->key, 0, cc->key_size * sizeof(u8)); + memzero_explicit(cc->key, cc->key_size); return ret; } @@ -3644,7 +3644,7 @@ static int crypt_message(struct dm_target *ti, unsigned int argc, char **argv, /* The key size may not be changed. */ key_size = get_key_size(&argv[2]); if (key_size < 0 || cc->key_size != key_size) { - memset(argv[2], '0', strlen(argv[2])); + memzero_explicit(argv[2], strlen(argv[2])); return -EINVAL; } @@ -3655,7 +3655,7 @@ static int crypt_message(struct dm_target *ti, unsigned int argc, char **argv, ret = cc->iv_gen_ops->init(cc); /* wipe the kernel key payload copy */ if (cc->key_string) - memset(cc->key, 0, cc->key_size * sizeof(u8)); + memzero_explicit(cc->key, cc->key_size); return ret; } if (argc == 2 && !strcasecmp(argv[1], "wipe"))