From patchwork Fri Mar 13 15:21:00 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 11437105 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 5AD0992A for ; Fri, 13 Mar 2020 15:21:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2795720749 for ; Fri, 13 Mar 2020 15:21:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="QO+lApy4" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726871AbgCMPVe (ORCPT ); Fri, 13 Mar 2020 11:21:34 -0400 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:55512 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726828AbgCMPVd (ORCPT ); Fri, 13 Mar 2020 11:21:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584112892; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:in-reply-to:in-reply-to:references:references; bh=PIUUoNv7asuvRGJ3bimRYxWwxxu6QQWq1QLXsN+FF7I=; b=QO+lApy4bqe+a4h541FbIb6U045m+etnZPbQE8bGA+zaTV4Vq9URrADr/ojQKgF9iuGUDM itvAAKYWiUDhqur8TVHIPzlCPdlGWXongoO+ASDF0hpa/A+uZCgUYUS25qZoapIRCmvIWr kqI2LkO7UAsybgAceo/mOHI9428ELJI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-220-s8Lk98ohOYyhBL167SFXwg-1; Fri, 13 Mar 2020 11:21:27 -0400 X-MC-Unique: s8Lk98ohOYyhBL167SFXwg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D414110821F2; Fri, 13 Mar 2020 15:21:25 +0000 (UTC) Received: from llong.com (ovpn-125-21.rdu2.redhat.com [10.10.125.21]) by smtp.corp.redhat.com (Postfix) with ESMTP id B9A9E91D64; Fri, 13 Mar 2020 15:21:23 +0000 (UTC) From: Waiman Long To: David Howells , Jarkko Sakkinen , James Morris , "Serge E. Hallyn" , Mimi Zohar Cc: keyrings@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org, Sumit Garg , Jerry Snitselaar , Roberto Sassu , Eric Biggers , Chris von Recklinghausen , Waiman Long Subject: [PATCH v3 1/3] KEYS: Don't write out to userspace while holding key semaphore Date: Fri, 13 Mar 2020 11:21:00 -0400 Message-Id: <20200313152102.1707-2-longman@redhat.com> In-Reply-To: <20200313152102.1707-1-longman@redhat.com> References: <20200313152102.1707-1-longman@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: A lockdep circular locking dependency report was seen when running a keyutils test: [12537.027242] ====================================================== [12537.059309] WARNING: possible circular locking dependency detected [12537.088148] 4.18.0-147.7.1.el8_1.x86_64+debug #1 Tainted: G OE --------- - - [12537.125253] ------------------------------------------------------ [12537.153189] keyctl/25598 is trying to acquire lock: [12537.175087] 000000007c39f96c (&mm->mmap_sem){++++}, at: __might_fault+0xc4/0x1b0 [12537.208365] [12537.208365] but task is already holding lock: [12537.234507] 000000003de5b58d (&type->lock_class){++++}, at: keyctl_read_key+0x15a/0x220 [12537.270476] [12537.270476] which lock already depends on the new lock. [12537.270476] [12537.307209] [12537.307209] the existing dependency chain (in reverse order) is: [12537.340754] [12537.340754] -> #3 (&type->lock_class){++++}: [12537.367434] down_write+0x4d/0x110 [12537.385202] __key_link_begin+0x87/0x280 [12537.405232] request_key_and_link+0x483/0xf70 [12537.427221] request_key+0x3c/0x80 [12537.444839] dns_query+0x1db/0x5a5 [dns_resolver] [12537.468445] dns_resolve_server_name_to_ip+0x1e1/0x4d0 [cifs] [12537.496731] cifs_reconnect+0xe04/0x2500 [cifs] [12537.519418] cifs_readv_from_socket+0x461/0x690 [cifs] [12537.546263] cifs_read_from_socket+0xa0/0xe0 [cifs] [12537.573551] cifs_demultiplex_thread+0x311/0x2db0 [cifs] [12537.601045] kthread+0x30c/0x3d0 [12537.617906] ret_from_fork+0x3a/0x50 [12537.636225] [12537.636225] -> #2 (root_key_user.cons_lock){+.+.}: [12537.664525] __mutex_lock+0x105/0x11f0 [12537.683734] request_key_and_link+0x35a/0xf70 [12537.705640] request_key+0x3c/0x80 [12537.723304] dns_query+0x1db/0x5a5 [dns_resolver] [12537.746773] dns_resolve_server_name_to_ip+0x1e1/0x4d0 [cifs] [12537.775607] cifs_reconnect+0xe04/0x2500 [cifs] [12537.798322] cifs_readv_from_socket+0x461/0x690 [cifs] [12537.823369] cifs_read_from_socket+0xa0/0xe0 [cifs] [12537.847262] cifs_demultiplex_thread+0x311/0x2db0 [cifs] [12537.873477] kthread+0x30c/0x3d0 [12537.890281] ret_from_fork+0x3a/0x50 [12537.908649] [12537.908649] -> #1 (&tcp_ses->srv_mutex){+.+.}: [12537.935225] __mutex_lock+0x105/0x11f0 [12537.954450] cifs_call_async+0x102/0x7f0 [cifs] [12537.977250] smb2_async_readv+0x6c3/0xc90 [cifs] [12538.000659] cifs_readpages+0x120a/0x1e50 [cifs] [12538.023920] read_pages+0xf5/0x560 [12538.041583] __do_page_cache_readahead+0x41d/0x4b0 [12538.067047] ondemand_readahead+0x44c/0xc10 [12538.092069] filemap_fault+0xec1/0x1830 [12538.111637] __do_fault+0x82/0x260 [12538.129216] do_fault+0x419/0xfb0 [12538.146390] __handle_mm_fault+0x862/0xdf0 [12538.167408] handle_mm_fault+0x154/0x550 [12538.187401] __do_page_fault+0x42f/0xa60 [12538.207395] do_page_fault+0x38/0x5e0 [12538.225777] page_fault+0x1e/0x30 [12538.243010] [12538.243010] -> #0 (&mm->mmap_sem){++++}: [12538.267875] lock_acquire+0x14c/0x420 [12538.286848] __might_fault+0x119/0x1b0 [12538.306006] keyring_read_iterator+0x7e/0x170 [12538.327936] assoc_array_subtree_iterate+0x97/0x280 [12538.352154] keyring_read+0xe9/0x110 [12538.370558] keyctl_read_key+0x1b9/0x220 [12538.391470] do_syscall_64+0xa5/0x4b0 [12538.410511] entry_SYSCALL_64_after_hwframe+0x6a/0xdf [12538.435535] [12538.435535] other info that might help us debug this: [12538.435535] [12538.472829] Chain exists of: [12538.472829] &mm->mmap_sem --> root_key_user.cons_lock --> &type->lock_class [12538.472829] [12538.524820] Possible unsafe locking scenario: [12538.524820] [12538.551431] CPU0 CPU1 [12538.572654] ---- ---- [12538.595865] lock(&type->lock_class); [12538.613737] lock(root_key_user.cons_lock); [12538.644234] lock(&type->lock_class); [12538.672410] lock(&mm->mmap_sem); [12538.687758] [12538.687758] *** DEADLOCK *** [12538.687758] [12538.714455] 1 lock held by keyctl/25598: [12538.732097] #0: 000000003de5b58d (&type->lock_class){++++}, at: keyctl_read_key+0x15a/0x220 [12538.770573] [12538.770573] stack backtrace: [12538.790136] CPU: 2 PID: 25598 Comm: keyctl Kdump: loaded Tainted: G [12538.844855] Hardware name: HP ProLiant DL360 Gen9/ProLiant DL360 Gen9, BIOS P89 12/27/2015 [12538.881963] Call Trace: [12538.892897] dump_stack+0x9a/0xf0 [12538.907908] print_circular_bug.isra.25.cold.50+0x1bc/0x279 [12538.932891] ? save_trace+0xd6/0x250 [12538.948979] check_prev_add.constprop.32+0xc36/0x14f0 [12538.971643] ? keyring_compare_object+0x104/0x190 [12538.992738] ? check_usage+0x550/0x550 [12539.009845] ? sched_clock+0x5/0x10 [12539.025484] ? sched_clock_cpu+0x18/0x1e0 [12539.043555] __lock_acquire+0x1f12/0x38d0 [12539.061551] ? trace_hardirqs_on+0x10/0x10 [12539.080554] lock_acquire+0x14c/0x420 [12539.100330] ? __might_fault+0xc4/0x1b0 [12539.119079] __might_fault+0x119/0x1b0 [12539.135869] ? __might_fault+0xc4/0x1b0 [12539.153234] keyring_read_iterator+0x7e/0x170 [12539.172787] ? keyring_read+0x110/0x110 [12539.190059] assoc_array_subtree_iterate+0x97/0x280 [12539.211526] keyring_read+0xe9/0x110 [12539.227561] ? keyring_gc_check_iterator+0xc0/0xc0 [12539.249076] keyctl_read_key+0x1b9/0x220 [12539.266660] do_syscall_64+0xa5/0x4b0 [12539.283091] entry_SYSCALL_64_after_hwframe+0x6a/0xdf One way to prevent this deadlock scenario from happening is to not allow writing to userspace while holding the key semaphore. Instead, an internal buffer is allocated for getting the keys out from the read method first before copying them out to userspace without holding the lock. That requires taking out the __user modifier from the read methods as well as additional changes to not use any userspace write helpers. Signed-off-by: Waiman Long Reviewed-by: Jarkko Sakkinen --- include/linux/key-type.h | 2 +- security/keys/big_key.c | 11 ++--- security/keys/encrypted-keys/encrypted.c | 7 ++- security/keys/keyctl.c | 57 +++++++++++++++++++---- security/keys/keyring.c | 6 +-- security/keys/request_key_auth.c | 7 ++- security/keys/trusted-keys/trusted_tpm1.c | 14 +----- security/keys/user_defined.c | 5 +- 8 files changed, 65 insertions(+), 44 deletions(-) diff --git a/include/linux/key-type.h b/include/linux/key-type.h index 4ded94bcf274..2ab2d6d6aeab 100644 --- a/include/linux/key-type.h +++ b/include/linux/key-type.h @@ -127,7 +127,7 @@ struct key_type { * much is copied into the buffer * - shouldn't do the copy if the buffer is NULL */ - long (*read)(const struct key *key, char __user *buffer, size_t buflen); + long (*read)(const struct key *key, char *buffer, size_t buflen); /* handle request_key() for this type instead of invoking * /sbin/request-key (optional) diff --git a/security/keys/big_key.c b/security/keys/big_key.c index 001abe530a0d..82008f900930 100644 --- a/security/keys/big_key.c +++ b/security/keys/big_key.c @@ -352,7 +352,7 @@ void big_key_describe(const struct key *key, struct seq_file *m) * read the key data * - the key's semaphore is read-locked */ -long big_key_read(const struct key *key, char __user *buffer, size_t buflen) +long big_key_read(const struct key *key, char *buffer, size_t buflen) { size_t datalen = (size_t)key->payload.data[big_key_len]; long ret; @@ -391,9 +391,8 @@ long big_key_read(const struct key *key, char __user *buffer, size_t buflen) ret = datalen; - /* copy decrypted data to user */ - if (copy_to_user(buffer, buf->virt, datalen) != 0) - ret = -EFAULT; + /* copy out decrypted data */ + memcpy(buffer, buf->virt, datalen); err_fput: fput(file); @@ -401,9 +400,7 @@ long big_key_read(const struct key *key, char __user *buffer, size_t buflen) big_key_free_buffer(buf); } else { ret = datalen; - if (copy_to_user(buffer, key->payload.data[big_key_data], - datalen) != 0) - ret = -EFAULT; + memcpy(buffer, key->payload.data[big_key_data], datalen); } return ret; diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c index 60720f58cbe0..f6797ba44bf7 100644 --- a/security/keys/encrypted-keys/encrypted.c +++ b/security/keys/encrypted-keys/encrypted.c @@ -902,14 +902,14 @@ static int encrypted_update(struct key *key, struct key_preparsed_payload *prep) } /* - * encrypted_read - format and copy the encrypted data to userspace + * encrypted_read - format and copy out the encrypted data * * The resulting datablob format is: * * * On success, return to userspace the encrypted key datablob size. */ -static long encrypted_read(const struct key *key, char __user *buffer, +static long encrypted_read(const struct key *key, char *buffer, size_t buflen) { struct encrypted_key_payload *epayload; @@ -957,8 +957,7 @@ static long encrypted_read(const struct key *key, char __user *buffer, key_put(mkey); memzero_explicit(derived_key, sizeof(derived_key)); - if (copy_to_user(buffer, ascii_buf, asciiblob_len) != 0) - ret = -EFAULT; + memcpy(buffer, ascii_buf, asciiblob_len); kzfree(ascii_buf); return asciiblob_len; diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c index 9b898c969558..81f68e434b9f 100644 --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -797,6 +797,21 @@ long keyctl_keyring_search(key_serial_t ringid, return ret; } +/* + * Call the read method + */ +static long __keyctl_read_key(struct key *key, char *buffer, size_t buflen) +{ + long ret; + + down_read(&key->sem); + ret = key_validate(key); + if (ret == 0) + ret = key->type->read(key, buffer, buflen); + up_read(&key->sem); + return ret; +} + /* * Read a key's payload. * @@ -844,16 +859,42 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen) /* the key is probably readable - now try to read it */ can_read_key: - ret = -EOPNOTSUPP; - if (key->type->read) { - /* Read the data with the semaphore held (since we might sleep) + if (!key->type->read) { + ret = -EOPNOTSUPP; + goto error2; + } + + if (!buffer || !buflen) { + /* Get the key length from the read method */ + ret = __keyctl_read_key(key, NULL, 0); + } else { + + /* + * Read the data with the semaphore held (since we might sleep) * to protect against the key being updated or revoked. + * + * Allocating a temporary buffer to hold the keys before + * transferring them to user buffer to avoid potential + * deadlock involving page fault and mmap_sem. + */ + char *tmpbuf = kmalloc(buflen, GFP_KERNEL); + + if (!tmpbuf) { + ret = -ENOMEM; + goto error2; + } + ret = __keyctl_read_key(key, tmpbuf, buflen); + + /* + * Read methods will just return the required length + * without any copying if the provided length isn't big + * enough. */ - down_read(&key->sem); - ret = key_validate(key); - if (ret == 0) - ret = key->type->read(key, buffer, buflen); - up_read(&key->sem); + if ((ret > 0) && (ret <= buflen)) { + if (copy_to_user(buffer, tmpbuf, ret)) + ret = -EFAULT; + } + kzfree(tmpbuf); } error2: diff --git a/security/keys/keyring.c b/security/keys/keyring.c index febf36c6ddc5..5ca620d31cd3 100644 --- a/security/keys/keyring.c +++ b/security/keys/keyring.c @@ -459,7 +459,6 @@ static int keyring_read_iterator(const void *object, void *data) { struct keyring_read_iterator_context *ctx = data; const struct key *key = keyring_ptr_to_key(object); - int ret; kenter("{%s,%d},,{%zu/%zu}", key->type->name, key->serial, ctx->count, ctx->buflen); @@ -467,10 +466,7 @@ static int keyring_read_iterator(const void *object, void *data) if (ctx->count >= ctx->buflen) return 1; - ret = put_user(key->serial, ctx->buffer); - if (ret < 0) - return ret; - ctx->buffer++; + *ctx->buffer++ = key->serial; ctx->count += sizeof(key->serial); return 0; } diff --git a/security/keys/request_key_auth.c b/security/keys/request_key_auth.c index ecba39c93fd9..41e9735006d0 100644 --- a/security/keys/request_key_auth.c +++ b/security/keys/request_key_auth.c @@ -22,7 +22,7 @@ static int request_key_auth_instantiate(struct key *, static void request_key_auth_describe(const struct key *, struct seq_file *); static void request_key_auth_revoke(struct key *); static void request_key_auth_destroy(struct key *); -static long request_key_auth_read(const struct key *, char __user *, size_t); +static long request_key_auth_read(const struct key *, char *, size_t); /* * The request-key authorisation key type definition. @@ -80,7 +80,7 @@ static void request_key_auth_describe(const struct key *key, * - the key's semaphore is read-locked */ static long request_key_auth_read(const struct key *key, - char __user *buffer, size_t buflen) + char *buffer, size_t buflen) { struct request_key_auth *rka = dereference_key_locked(key); size_t datalen; @@ -97,8 +97,7 @@ static long request_key_auth_read(const struct key *key, if (buflen > datalen) buflen = datalen; - if (copy_to_user(buffer, rka->callout_info, buflen) != 0) - ret = -EFAULT; + memcpy(buffer, rka->callout_info, buflen); } return ret; diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c index d2c5ec1e040b..8001ab07e63b 100644 --- a/security/keys/trusted-keys/trusted_tpm1.c +++ b/security/keys/trusted-keys/trusted_tpm1.c @@ -1130,11 +1130,10 @@ static int trusted_update(struct key *key, struct key_preparsed_payload *prep) * trusted_read - copy the sealed blob data to userspace in hex. * On success, return to userspace the trusted key datablob size. */ -static long trusted_read(const struct key *key, char __user *buffer, +static long trusted_read(const struct key *key, char *buffer, size_t buflen) { const struct trusted_key_payload *p; - char *ascii_buf; char *bufp; int i; @@ -1143,18 +1142,9 @@ static long trusted_read(const struct key *key, char __user *buffer, return -EINVAL; if (buffer && buflen >= 2 * p->blob_len) { - ascii_buf = kmalloc_array(2, p->blob_len, GFP_KERNEL); - if (!ascii_buf) - return -ENOMEM; - - bufp = ascii_buf; + bufp = buffer; for (i = 0; i < p->blob_len; i++) bufp = hex_byte_pack(bufp, p->blob[i]); - if (copy_to_user(buffer, ascii_buf, 2 * p->blob_len) != 0) { - kzfree(ascii_buf); - return -EFAULT; - } - kzfree(ascii_buf); } return 2 * p->blob_len; } diff --git a/security/keys/user_defined.c b/security/keys/user_defined.c index 6f12de4ce549..07d4287e9084 100644 --- a/security/keys/user_defined.c +++ b/security/keys/user_defined.c @@ -168,7 +168,7 @@ EXPORT_SYMBOL_GPL(user_describe); * read the key data * - the key's semaphore is read-locked */ -long user_read(const struct key *key, char __user *buffer, size_t buflen) +long user_read(const struct key *key, char *buffer, size_t buflen) { const struct user_key_payload *upayload; long ret; @@ -181,8 +181,7 @@ long user_read(const struct key *key, char __user *buffer, size_t buflen) if (buflen > upayload->datalen) buflen = upayload->datalen; - if (copy_to_user(buffer, upayload->data, buflen) != 0) - ret = -EFAULT; + memcpy(buffer, upayload->data, buflen); } return ret; From patchwork Fri Mar 13 15:21:01 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 11437101 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A85CF13B1 for ; Fri, 13 Mar 2020 15:21:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 888942074D for ; Fri, 13 Mar 2020 15:21:45 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="HI7pP3qm" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726998AbgCMPVo (ORCPT ); Fri, 13 Mar 2020 11:21:44 -0400 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:27316 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726681AbgCMPVf (ORCPT ); Fri, 13 Mar 2020 11:21:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584112894; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:in-reply-to:in-reply-to:references:references; bh=IgMdwtUBEGAuM/8z5e97O8Otg6NfgxXQdFDc4jd+DZ0=; b=HI7pP3qmZp4wLPpLWhs902AtRKBnJ4juj3R8nt7Mb4VVCALqWwZoK+d6PCM0fA6ZYJjnko iUrmiAIj2A0gE07Mi76XBYR/fuZE8+OWxZ3tWynhSU4L19ydyx5Gwfg08wfAwe4+Gv+37r YOiKY0ujYz5SjTiDUwS10sxY7+v6dEQ= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-415-7l5v2bgOOHicxRo9VhQqFw-1; Fri, 13 Mar 2020 11:21:30 -0400 X-MC-Unique: 7l5v2bgOOHicxRo9VhQqFw-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 14CE8107B767; Fri, 13 Mar 2020 15:21:28 +0000 (UTC) Received: from llong.com (ovpn-125-21.rdu2.redhat.com [10.10.125.21]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1316492D30; Fri, 13 Mar 2020 15:21:25 +0000 (UTC) From: Waiman Long To: David Howells , Jarkko Sakkinen , James Morris , "Serge E. Hallyn" , Mimi Zohar Cc: keyrings@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org, Sumit Garg , Jerry Snitselaar , Roberto Sassu , Eric Biggers , Chris von Recklinghausen , Waiman Long Subject: [PATCH v3 2/3] KEYS: Avoid false positive ENOMEM error on key read Date: Fri, 13 Mar 2020 11:21:01 -0400 Message-Id: <20200313152102.1707-3-longman@redhat.com> In-Reply-To: <20200313152102.1707-1-longman@redhat.com> References: <20200313152102.1707-1-longman@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: By allocating a kernel buffer with an user-supplied buffer length, it is possible that a false positive ENOMEM error may be returned because the user-supplied length is just too large even if the system do have enough memory to hold the actual key data. To reduce this possibility, we set a threshold (1024) over which we do check the actual key length first before allocating a buffer of the right size to hold it. Signed-off-by: Waiman Long --- security/keys/keyctl.c | 48 ++++++++++++++++++++++++++++++++---------- 1 file changed, 37 insertions(+), 11 deletions(-) diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c index 81f68e434b9f..a05a4dd2f9ce 100644 --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -877,24 +877,50 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen) * transferring them to user buffer to avoid potential * deadlock involving page fault and mmap_sem. */ - char *tmpbuf = kmalloc(buflen, GFP_KERNEL); - - if (!tmpbuf) { - ret = -ENOMEM; - goto error2; - } - ret = __keyctl_read_key(key, tmpbuf, buflen); + char *tmpbuf = NULL; + size_t tmpbuflen = buflen; /* - * Read methods will just return the required length - * without any copying if the provided length isn't big - * enough. + * We don't want an erronous -ENOMEM error due to an + * arbitrary large user-supplied buflen. So if buflen + * exceeds a threshold (1024 bytes in this case), we call + * the read method twice. The first time to get the buffer + * length and the second time to read out the key data. + * + * N.B. All the read methods will return the required + * buffer length with a NULL input buffer or when + * the input buffer length isn't large enough. */ + if (buflen <= 0x400) { +allocbuf: + tmpbuf = kmalloc(tmpbuflen, GFP_KERNEL); + if (!tmpbuf) { + ret = -ENOMEM; + goto error2; + } + } + + ret = __keyctl_read_key(key, tmpbuf, tmpbuflen); if ((ret > 0) && (ret <= buflen)) { + /* + * It is possible, though unlikely, that the key + * changes in between the up_read->down_read period. + * If the key becomes longer, we will have to + * allocate a larger buffer and redo the key read + * again. + */ + if (!tmpbuf || unlikely(ret > tmpbuflen)) { + if (unlikely(tmpbuf)) + kzfree(tmpbuf); + tmpbuflen = ret; + goto allocbuf; + } + if (copy_to_user(buffer, tmpbuf, ret)) ret = -EFAULT; } - kzfree(tmpbuf); + if (tmpbuf) + kzfree(tmpbuf); } error2: From patchwork Fri Mar 13 15:21:02 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 11437095 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 4652616B1 for ; Fri, 13 Mar 2020 15:21:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 25AAC2074F for ; Fri, 13 Mar 2020 15:21:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="cbWP3/dz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726964AbgCMPVg (ORCPT ); Fri, 13 Mar 2020 11:21:36 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:24951 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726930AbgCMPVf (ORCPT ); Fri, 13 Mar 2020 11:21:35 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584112894; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:in-reply-to:in-reply-to:references:references; bh=Guy49jz/MclwiKRYm/R98tQ5vcDgMGGlebOY5cev/kE=; b=cbWP3/dzBMAID5PrHP4UrOXqg8FeKgrsiMHZCQgR5jXOOOARuG7jl4DquqpLnUZKHrfgwC 1jVe4Utt1p/swYLfl2/46K3TY13FbW6GLktAS09mwDLDLL58r3CCnimygxPkXSg527bTWU hgskuju5J0dzQP/lbHw18ZV4Q7zUpuA= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-5-VNOdMdZHMWGwBA7EAb8cFg-1; Fri, 13 Mar 2020 11:21:32 -0400 X-MC-Unique: VNOdMdZHMWGwBA7EAb8cFg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 4E882808245; Fri, 13 Mar 2020 15:21:30 +0000 (UTC) Received: from llong.com (ovpn-125-21.rdu2.redhat.com [10.10.125.21]) by smtp.corp.redhat.com (Postfix) with ESMTP id 46A8291D61; Fri, 13 Mar 2020 15:21:28 +0000 (UTC) From: Waiman Long To: David Howells , Jarkko Sakkinen , James Morris , "Serge E. Hallyn" , Mimi Zohar Cc: keyrings@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-integrity@vger.kernel.org, Sumit Garg , Jerry Snitselaar , Roberto Sassu , Eric Biggers , Chris von Recklinghausen , Waiman Long Subject: [PATCH v3 3/3] KEYS: Use kvmalloc() to better handle large buffer allocation Date: Fri, 13 Mar 2020 11:21:02 -0400 Message-Id: <20200313152102.1707-4-longman@redhat.com> In-Reply-To: <20200313152102.1707-1-longman@redhat.com> References: <20200313152102.1707-1-longman@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: For large multi-page temporary buffer allocation, the security/keys subsystem don't need contiguous physical pages. It will work perfectly fine with virtually mapped pages. Replace the kmalloc() call by kvmalloc() and provide a __kvzfree() helper function to clear and free the kvmalloc'ed buffer. This will reduce the chance of memory allocation failure just because of highly fragmented pages. Suggested-by: David Howells Signed-off-by: Waiman Long --- security/keys/internal.h | 14 ++++++++++++++ security/keys/keyctl.c | 10 +++++----- 2 files changed, 19 insertions(+), 5 deletions(-) diff --git a/security/keys/internal.h b/security/keys/internal.h index ba3e2da14cef..855b11eb73ee 100644 --- a/security/keys/internal.h +++ b/security/keys/internal.h @@ -16,6 +16,8 @@ #include #include #include +#include +#include struct iovec; @@ -349,4 +351,16 @@ static inline void key_check(const struct key *key) #endif +/* + * Helper function to clear and free a kvmalloc'ed memory object. + */ +static inline void __kvzfree(const void *addr, size_t len) +{ + if (is_vmalloc_addr(addr)) { + memset((void *)addr, 0, len); + vfree(addr); + } else { + kzfree(addr); + } +} #endif /* _INTERNAL_H */ diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c index a05a4dd2f9ce..878259cf35d5 100644 --- a/security/keys/keyctl.c +++ b/security/keys/keyctl.c @@ -339,7 +339,7 @@ long keyctl_update_key(key_serial_t id, payload = NULL; if (plen) { ret = -ENOMEM; - payload = kmalloc(plen, GFP_KERNEL); + payload = kvmalloc(plen, GFP_KERNEL); if (!payload) goto error; @@ -360,7 +360,7 @@ long keyctl_update_key(key_serial_t id, key_ref_put(key_ref); error2: - kzfree(payload); + __kvzfree(payload, plen); error: return ret; } @@ -893,7 +893,7 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen) */ if (buflen <= 0x400) { allocbuf: - tmpbuf = kmalloc(tmpbuflen, GFP_KERNEL); + tmpbuf = kvmalloc(tmpbuflen, GFP_KERNEL); if (!tmpbuf) { ret = -ENOMEM; goto error2; @@ -911,7 +911,7 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen) */ if (!tmpbuf || unlikely(ret > tmpbuflen)) { if (unlikely(tmpbuf)) - kzfree(tmpbuf); + __kvzfree(tmpbuf, tmpbuflen); tmpbuflen = ret; goto allocbuf; } @@ -920,7 +920,7 @@ long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen) ret = -EFAULT; } if (tmpbuf) - kzfree(tmpbuf); + __kvzfree(tmpbuf, tmpbuflen); } error2: