From patchwork Thu Mar 23 13:04:12 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Petr Pavlu X-Patchwork-Id: 13185632 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 D4740C6FD1D for ; Thu, 23 Mar 2023 13:04:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231308AbjCWNEf (ORCPT ); Thu, 23 Mar 2023 09:04:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53266 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230059AbjCWNEc (ORCPT ); Thu, 23 Mar 2023 09:04:32 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1F2B71DBA2; Thu, 23 Mar 2023 06:04:26 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id A783B1FDD4; Thu, 23 Mar 2023 13:04:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1679576665; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=4w/uym1UjHPw2V6NrSEuzlrM6thISw+AgzpQZUHtyJo=; b=f9Z3Na+Qg8O5LuK7qysZrlDjoB23gWQ3FRMaLGnF0UYJI+QeSFbfygArABAKtK0vJ4KWrR yPit4CDE/L5dZquSGyZOL9HBsGWj1ugntc02s+tjws4TnUueiosaNazWP/grI/O3rmRx0w Xb9SbP+yqe/R5WzYy6nO6vOORwt6wrE= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 84FC013596; Thu, 23 Mar 2023 13:04:25 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id d3F3H1lOHGRpSwAAMHmgww (envelope-from ); Thu, 23 Mar 2023 13:04:25 +0000 From: Petr Pavlu To: dhowells@redhat.com, jarkko@kernel.org Cc: keyrings@vger.kernel.org, linux-kernel@vger.kernel.org, Petr Pavlu Subject: [PATCH] keys: Fix linking a duplicate key to a keyring's assoc_array Date: Thu, 23 Mar 2023 14:04:12 +0100 Message-Id: <20230323130412.32097-1-petr.pavlu@suse.com> X-Mailer: git-send-email 2.35.3 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: keyrings@vger.kernel.org When making a DNS query inside the kernel using dns_query(), the request code can in rare cases end up creating a duplicate index key in the assoc_array of the destination keyring. It is eventually found by a BUG_ON() check in the assoc_array implementation and results in a crash. Example report: [2158499.700025] kernel BUG at ../lib/assoc_array.c:652! [2158499.700039] invalid opcode: 0000 [#1] SMP PTI [2158499.700065] CPU: 3 PID: 31985 Comm: kworker/3:1 Kdump: loaded Not tainted 5.3.18-150300.59.90-default #1 SLE15-SP3 [2158499.700096] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020 [2158499.700351] Workqueue: cifsiod cifs_resolve_server [cifs] [2158499.700380] RIP: 0010:assoc_array_insert+0x85f/0xa40 [2158499.700401] Code: ff 74 2b 48 8b 3b 49 8b 45 18 4c 89 e6 48 83 e7 fe e8 95 ec 74 00 3b 45 88 7d db 85 c0 79 d4 0f 0b 0f 0b 0f 0b e8 41 f2 be ff <0f> 0b 0f 0b 81 7d 88 ff ff ff 7f 4c 89 eb 4c 8b ad 58 ff ff ff 0f [2158499.700448] RSP: 0018:ffffc0bd6187faf0 EFLAGS: 00010282 [2158499.700470] RAX: ffff9f1ea7da2fe8 RBX: ffff9f1ea7da2fc1 RCX: 0000000000000005 [2158499.700492] RDX: 0000000000000000 RSI: 0000000000000005 RDI: 0000000000000000 [2158499.700515] RBP: ffffc0bd6187fbb0 R08: ffff9f185faf1100 R09: 0000000000000000 [2158499.700538] R10: ffff9f1ea7da2cc0 R11: 000000005ed8cec8 R12: ffffc0bd6187fc28 [2158499.700561] R13: ffff9f15feb8d000 R14: ffff9f1ea7da2fc0 R15: ffff9f168dc0d740 [2158499.700585] FS: 0000000000000000(0000) GS:ffff9f185fac0000(0000) knlGS:0000000000000000 [2158499.700610] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [2158499.700630] CR2: 00007fdd94fca238 CR3: 0000000809d8c006 CR4: 00000000003706e0 [2158499.700702] Call Trace: [2158499.700741] ? key_alloc+0x447/0x4b0 [2158499.700768] ? __key_link_begin+0x43/0xa0 [2158499.700790] __key_link_begin+0x43/0xa0 [2158499.700814] request_key_and_link+0x2c7/0x730 [2158499.700847] ? dns_resolver_read+0x20/0x20 [dns_resolver] [2158499.700873] ? key_default_cmp+0x20/0x20 [2158499.700898] request_key_tag+0x43/0xa0 [2158499.700926] dns_query+0x114/0x2ca [dns_resolver] [2158499.701127] dns_resolve_server_name_to_ip+0x194/0x310 [cifs] [2158499.701164] ? scnprintf+0x49/0x90 [2158499.701190] ? __switch_to_asm+0x40/0x70 [2158499.701211] ? __switch_to_asm+0x34/0x70 [2158499.701405] reconn_set_ipaddr_from_hostname+0x81/0x2a0 [cifs] [2158499.701603] cifs_resolve_server+0x4b/0xd0 [cifs] [2158499.701632] process_one_work+0x1f8/0x3e0 [2158499.701658] worker_thread+0x2d/0x3f0 [2158499.701682] ? process_one_work+0x3e0/0x3e0 [2158499.701703] kthread+0x10d/0x130 [2158499.701723] ? kthread_park+0xb0/0xb0 [2158499.701746] ret_from_fork+0x1f/0x40 The situation occurs as follows: * Some kernel facility invokes dns_query() to resolve a hostname, for example, "abcdef". The function registers its global DNS resolver cache as current->cred.thread_keyring and passes the query to request_key_net() -> request_key_tag() -> request_key_and_link(). * Function request_key_and_link() creates a keyring_search_context object. Its match_data.cmp method gets set via a call to type->match_preparse() (resolves to dns_resolver_match_preparse()) to dns_resolver_cmp(). * Function request_key_and_link() continues and invokes search_process_keyrings_rcu() which returns that a given key was not found. The control is then passed to request_key_and_link() -> construct_alloc_key(). * Concurrently to that, a second task similarly makes a DNS query for "abcdef." and its result gets inserted into the DNS resolver cache. * Back on the first task, function construct_alloc_key() first runs __key_link_begin() to determine an assoc_array_edit operation to insert a new key. Index keys in the array are compared exactly as-is, using keyring_compare_object(). The operation finds that "abcdef" is not yet present in the destination keyring. * Function construct_alloc_key() continues and checks if a given key is already present on some keyring by again calling search_process_keyrings_rcu(). This search is done using dns_resolver_cmp() and "abcdef" gets matched with now present key "abcdef.". * The found key is linked on the destination keyring by calling __key_link() and using the previously calculated assoc_array_edit operation. This inserts the "abcdef." key in the array but creates a duplicity because the same index key is already present. Fix the problem by postponing __key_link_begin() in construct_alloc_key() until an actual key which should be linked into the destination keyring is determined. Signed-off-by: Petr Pavlu Reviewed-by: Jarkko Sakkinen Reviewed-by: Joey Lee --- security/keys/request_key.c | 35 ++++++++++++++++++++++++----------- 1 file changed, 24 insertions(+), 11 deletions(-) diff --git a/security/keys/request_key.c b/security/keys/request_key.c index 2da4404276f0..04eb7e4cedad 100644 --- a/security/keys/request_key.c +++ b/security/keys/request_key.c @@ -398,17 +398,21 @@ static int construct_alloc_key(struct keyring_search_context *ctx, set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags); if (dest_keyring) { - ret = __key_link_lock(dest_keyring, &ctx->index_key); + ret = __key_link_lock(dest_keyring, &key->index_key); if (ret < 0) goto link_lock_failed; - ret = __key_link_begin(dest_keyring, &ctx->index_key, &edit); - if (ret < 0) - goto link_prealloc_failed; } - /* attach the key to the destination keyring under lock, but we do need + /* + * Attach the key to the destination keyring under lock, but we do need * to do another check just in case someone beat us to it whilst we - * waited for locks */ + * waited for locks. + * + * The caller might specify a comparison function which looks for keys + * that do not exactly match but are still equivalent from the caller's + * perspective. The __key_link_begin() operation must be done only after + * an actual key is determined. + */ mutex_lock(&key_construction_mutex); rcu_read_lock(); @@ -417,12 +421,16 @@ static int construct_alloc_key(struct keyring_search_context *ctx, if (!IS_ERR(key_ref)) goto key_already_present; - if (dest_keyring) + if (dest_keyring) { + ret = __key_link_begin(dest_keyring, &key->index_key, &edit); + if (ret < 0) + goto link_alloc_failed; __key_link(dest_keyring, key, &edit); + } mutex_unlock(&key_construction_mutex); if (dest_keyring) - __key_link_end(dest_keyring, &ctx->index_key, edit); + __key_link_end(dest_keyring, &key->index_key, edit); mutex_unlock(&user->cons_lock); *_key = key; kleave(" = 0 [%d]", key_serial(key)); @@ -435,10 +443,13 @@ static int construct_alloc_key(struct keyring_search_context *ctx, mutex_unlock(&key_construction_mutex); key = key_ref_to_ptr(key_ref); if (dest_keyring) { + ret = __key_link_begin(dest_keyring, &key->index_key, &edit); + if (ret < 0) + goto link_alloc_failed_unlocked; ret = __key_link_check_live_key(dest_keyring, key); if (ret == 0) __key_link(dest_keyring, key, &edit); - __key_link_end(dest_keyring, &ctx->index_key, edit); + __key_link_end(dest_keyring, &key->index_key, edit); if (ret < 0) goto link_check_failed; } @@ -453,8 +464,10 @@ static int construct_alloc_key(struct keyring_search_context *ctx, kleave(" = %d [linkcheck]", ret); return ret; -link_prealloc_failed: - __key_link_end(dest_keyring, &ctx->index_key, edit); +link_alloc_failed: + mutex_unlock(&key_construction_mutex); +link_alloc_failed_unlocked: + __key_link_end(dest_keyring, &key->index_key, edit); link_lock_failed: mutex_unlock(&user->cons_lock); key_put(key);