From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from canpmsgout07.his.huawei.com (canpmsgout07.his.huawei.com [113.46.200.222]) (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 09F953C13EE for ; Mon, 31 Aug 2026 07:39:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=113.46.200.222 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788161992; cv=none; b=MtxmyZPUwcPa+EtcKq2Yqy8rKFDtZntZIsHJ34s/PVbjuXqpggH2sEntrRxvidxkEIiBW0v92boIiV97Te+e+lA/rigHr8+wHNhwnmIe2nA6Lj3B6TIowuhzF2zDs/o+k7gqiM4pFWJMwNCdLZnzQfv/LMBCewmoe6sA5ry/JBY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788161992; c=relaxed/simple; bh=rkO1JcrGztR2OSZCVLWbU4eEWXaPT6phPD6Usx2UUpE=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=rkkxhsZ+wRZO0hPRO2QXTK0QiCOq0JDd3StnAw4xFwVj9ry+2JcgvApGgoATjQxHcNVGr873Fhuul6zXdyWurhqmRuRwaAsg47EtTcFhHe2siz8v0d5J1eVTRMB9PbKzSwjVOcOaOkRXMu7FBgGa/ypVE7Ft54xzLrDsKtj6Sxk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b=s1DdZ87w; arc=none smtp.client-ip=113.46.200.222 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=huawei.com header.i=@huawei.com header.b="s1DdZ87w" dkim-signature: v=1; a=rsa-sha256; d=huawei.com; s=dkim; c=relaxed/relaxed; q=dns/txt; h=From; bh=65FDGHnCiKKtgz8gBgPjyNHG770Wgp2UgN2FNs1zkgg=; b=s1DdZ87wvVz0jwRB9bhZEceeo0NAqmw4W7sQm09oPj0zjsVwDBp3csQQkkWR3x/Wms/QMzL/w JAU+CjAZ4oRfX2TQLOgXNJ8M/S7EJJRxea0Re1FvrFzjCUuCPZQvV2gnwUz/3cpkvRwhh7dfp6C 1KiIZwLQ7uEAP+6KG/bNyN4= Received: from mail.maildlp.com (unknown [172.19.163.163]) by canpmsgout07.his.huawei.com (SkyGuard) with ESMTPS id 4hYLFr5rxNzLlYL; Mon, 31 Aug 2026 15:28:48 +0800 (CST) Received: from dggpemf500011.china.huawei.com (unknown [7.185.36.131]) by mail.maildlp.com (Postfix) with ESMTPS id 83F0C4048B; Mon, 31 Aug 2026 15:39:37 +0800 (CST) Received: from [10.67.109.254] (10.67.109.254) by dggpemf500011.china.huawei.com (7.185.36.131) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Mon, 31 Aug 2026 15:39:36 +0800 Message-ID: <76f634e3-9adb-4ae2-b2b0-a7e13a2f93c3@huawei.com> Date: Mon, 31 Aug 2026 15:39:35 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 1/9] crash_dump: Fix potential double free and UAF of keys_header To: Coiby Xu , CC: Andrew Morton , Sourabh Jain , Baoquan He , Dave Young , Pratyush Yadav , Mike Rapoport , Pasha Tatashin , open list References: <20260828084900.1496839-1-coiby.xu@gmail.com> <20260828084900.1496839-2-coiby.xu@gmail.com> From: Jinjie Ruan In-Reply-To: <20260828084900.1496839-2-coiby.xu@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-ClientProxiedBy: kwepems100002.china.huawei.com (7.221.188.206) To dggpemf500011.china.huawei.com (7.185.36.131) 在 2026/8/28 16:48, Coiby Xu 写道: > If kexec_add_buffer somehow fails, keys_header will be freed. Depending > on /sys/kernel/config/crash_dm_crypt_key/reuse, it will lead to the > following two problems if the kexec_file_load syscall is called again, > 1. Double free of keys_header if reuse=false > 2. UAF of keys_header if reuse=true > > To address these problems and also make it easier to reason about the > code, keep two invariants, > 1. keys_header will always be freed at the end of kexec_file_load > syscall except during kdump image unloading for CPU/memory > hot-plugging support > 2. There will always be valid keys_header if reuse=true > > Fixes: 479e58549b0f ("crash_dump: store dm crypt keys in kdump reserved memory") > Fixes: 9ebfa8dcaea7 ("crash_dump: reuse saved dm crypt keys for CPU/memory hot-plugging") > Reported-by: Sourabh Jain > Signed-off-by: Coiby Xu > --- > include/linux/kexec.h | 6 ++++ > kernel/crash_dump_dm_crypt.c | 66 ++++++++++++++++++++++++++---------- > kernel/kexec_file.c | 2 ++ > 3 files changed, 56 insertions(+), 18 deletions(-) > > diff --git a/include/linux/kexec.h b/include/linux/kexec.h > index 0af8ae4fdd08..0fa8bac04576 100644 > --- a/include/linux/kexec.h > +++ b/include/linux/kexec.h > @@ -552,6 +552,12 @@ void set_kexec_sig_enforced(void); > static inline void set_kexec_sig_enforced(void) {} > #endif > > +#ifdef CONFIG_CRASH_DM_CRYPT > +void kexec_file_post_load_cleanup_dm_crypt(struct kimage *image); > +#else > +static inline void kexec_file_post_load_cleanup_dm_crypt(struct kimage *image) {} > +#endif > + > #endif /* !defined(__ASSEBMLY__) */ > > #endif /* LINUX_KEXEC_H */ > diff --git a/kernel/crash_dump_dm_crypt.c b/kernel/crash_dump_dm_crypt.c > index c685497cd470..4335b6cb1fc4 100644 > --- a/kernel/crash_dump_dm_crypt.c > +++ b/kernel/crash_dump_dm_crypt.c > @@ -84,18 +84,25 @@ static int add_key_to_keyring(struct dm_crypt_key *dm_key, > return r; > } > > -static void get_keys_from_kdump_reserved_memory(void) > +static int get_keys_from_kdump_reserved_memory(void) > { > struct keys_header *keys_header_loaded; > + size_t keys_header_size; > > - arch_kexec_unprotect_crashkres(); > + keys_header_size = get_keys_header_size(key_count); > + keys_header = kzalloc(keys_header_size, GFP_KERNEL); > + if (!keys_header) > + return -ENOMEM; > > + arch_kexec_unprotect_crashkres(); > keys_header_loaded = kmap_local_page(pfn_to_page( > kexec_crash_image->dm_crypt_keys_addr >> PAGE_SHIFT)); > > - memcpy(keys_header, keys_header_loaded, get_keys_header_size(key_count)); > + memcpy(keys_header, keys_header_loaded, keys_header_size); > kunmap_local(keys_header_loaded); > arch_kexec_protect_crashkres(); > + > + return 0; > } > > static int restore_dm_crypt_keys_to_thread_keyring(void) > @@ -286,17 +293,28 @@ static ssize_t config_keys_reuse_show(struct config_item *item, char *page) > static ssize_t config_keys_reuse_store(struct config_item *item, > const char *page, size_t count) > { > + bool val; > + int r; > + > if (!kexec_crash_image || !kexec_crash_image->dm_crypt_keys_addr) { > kexec_dprintk( > "dm-crypt keys haven't be saved to crash-reserved memory\n"); > return -EINVAL; > } > > - if (kstrtobool(page, &is_dm_key_reused)) > + if (kstrtobool(page, &val) || !val) > return -EINVAL; > > - if (is_dm_key_reused) > - get_keys_from_kdump_reserved_memory(); > + if (is_dm_key_reused) { > + pr_info("Already got dm-crypt keys, please continue with kexec_file_load syscall\n"); > + } else { > + r = get_keys_from_kdump_reserved_memory(); > + if (r) { > + pr_warn("Failed to get dm-crypt keys from reserved memory\n"); > + return r; > + } > + is_dm_key_reused = true; > + } > > return count; > } > @@ -369,9 +387,6 @@ static int build_keys_header(void) > struct config_key *key; > int i, r; > > - if (keys_header != NULL) > - kvfree(keys_header); > - > keys_header = kzalloc(get_keys_header_size(key_count), GFP_KERNEL); > if (!keys_header) > return -ENOMEM; > @@ -415,8 +430,7 @@ int crash_load_dm_crypt_keys(struct kimage *image) > .top_down = false, > .random = true, > }; > - int r; > - > + int r = 0; > > if (key_count <= 0) { > kexec_dprintk("No dm-crypt keys\n"); > @@ -424,14 +438,15 @@ int crash_load_dm_crypt_keys(struct kimage *image) > } > > if (!is_dm_key_reused) { > - image->dm_crypt_keys_addr = 0; > r = build_keys_header(); > - if (r) { > - pr_err("Failed to build dm-crypt keys header, ret=%d\n", r); > - return r; > - } > + if (r) > + goto out; > } > > + /* > + * keys_header will be copied to reserver memory later and then be > + * cleaned up at the end of kexec_file_load syscall > + */ > kbuf.buffer = keys_header; > kbuf.bufsz = get_keys_header_size(key_count); > > @@ -441,18 +456,33 @@ int crash_load_dm_crypt_keys(struct kimage *image) > r = kexec_add_buffer(&kbuf); > if (r) { > pr_err("Failed to call kexec_add_buffer, ret=%d\n", r); > - kvfree((void *)kbuf.buffer); > - return r; > + goto out; > } > + > image->dm_crypt_keys_addr = kbuf.mem; > image->dm_crypt_keys_sz = kbuf.bufsz; > kexec_dprintk( > "Loaded dm crypt keys to kexec_buffer bufsz=0x%lx memsz=0x%lx\n", > kbuf.bufsz, kbuf.memsz); > > +out: > + is_dm_key_reused = false; I think there's still a bug for arm64 here. When is_dm_key_reused set to true, the outer while loop prematurely clears the is_dm_key_reused flag at the end of crash_load_dm_crypt_keys() in the very first iteration. Consequently, subsequent re-entrant calls to crash_load_dm_crypt_keys() falsely perceive the keys as not reused, forcing a redundant execution of build_keys_header() which overwrites the global keys_header pointer; This induces a silent kernel memory leak. 92 >-------/* 93 >------- * The location of the kernel segment may make it impossible to satisfy 94 >------- * the other segment requirements, so we try repeatedly to find a 95 >------- * location that will work. 96 >------- */ 97 >-------while ((ret = kexec_add_buffer(&kbuf)) == 0) { 98 >------->-------/* Try to load additional data */ 99 >------->-------kernel_segment = &image->segment[kernel_segment_number]; 100 >------->-------ret = load_other_segments(image, kernel_segment->mem, 101 >------->------->------->------->------- kernel_segment->memsz, initrd, 102 >------->------->------->------->------- initrd_len, cmdline); 103 >------->-------if (!ret) 104 >------->------->-------break; 105 106 >------->-------/* 107 >------->------- * We couldn't find space for the other segments; erase the 108 >------->------- * kernel segment and try the next available hole. 109 >------->------- */ 110 >------->-------image->nr_segments -= 1; 111 >------->-------kbuf.buf_min = kernel_segment->mem + kernel_segment->memsz; 112 >------->-------kbuf.mem = KEXEC_BUF_MEM_UNKNOWN; 113 >-------} > return r; > } > > +void kexec_file_post_load_cleanup_dm_crypt(struct kimage *image) > +{ > + /* > + * For CPU/memory hot-plugging, the kdump image will be reloaded. Prevent > + * keys_header from being cleaned up during unloading when > + * is_dm_key_reused=true > + */ > + if (!is_dm_key_reused) { > + kfree_sensitive(keys_header); > + keys_header = NULL; > + } > +} > + > static int __init configfs_dmcrypt_keys_init(void) > { > int ret; > diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c > index 59fb9d71e9d8..062f7e79016d 100644 > --- a/kernel/kexec_file.c > +++ b/kernel/kexec_file.c > @@ -140,6 +140,8 @@ void kimage_file_post_load_cleanup(struct kimage *image) > kfree(image->image_loader_data); > image->image_loader_data = NULL; > > + kexec_file_post_load_cleanup_dm_crypt(image); > + > kexec_file_dbg_print = false; > } >