The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable@xxxxxxxxxxxxxxx>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x d55901522f96082a43b9842d34867363c0cdbac5 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2023072356-confirm-embezzle-c962@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^.. Possible dependencies: d55901522f96 ("keys: Fix linking a duplicate key to a keyring's assoc_array") f7e47677e39a ("watch_queue: Add a key/keyring notification facility") 0858caa419e6 ("uapi: General notification queue definitions") thanks, greg k-h ------------------ original commit in Linus's tree ------------------ >From d55901522f96082a43b9842d34867363c0cdbac5 Mon Sep 17 00:00:00 2001 From: Petr Pavlu <petr.pavlu@xxxxxxxx> Date: Thu, 23 Mar 2023 14:04:12 +0100 Subject: [PATCH] keys: Fix linking a duplicate key to a keyring's assoc_array 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. [jarkko@xxxxxxxxxx: added a fixes tag and cc to stable] Cc: stable@xxxxxxxxxxxxxxx # v5.3+ Fixes: df593ee23e05 ("keys: Hoist locking out of __key_link_begin()") Signed-off-by: Petr Pavlu <petr.pavlu@xxxxxxxx> Reviewed-by: Joey Lee <jlee@xxxxxxxx> Reviewed-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> Signed-off-by: Jarkko Sakkinen <jarkko@xxxxxxxxxx> diff --git a/security/keys/request_key.c b/security/keys/request_key.c index 07a0ef2baacd..a7673ad86d18 100644 --- a/security/keys/request_key.c +++ b/security/keys/request_key.c @@ -401,17 +401,21 @@ 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(); @@ -420,12 +424,16 @@ 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)); @@ -438,10 +446,13 @@ 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; } @@ -456,8 +467,10 @@ 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);
