kernel/git/stable/linux-stable.git/security/keys/keyring.c, branch linux-4.19.y

security/keys: fix slab-out-of-bounds in key_task_permission

2024-11-17T13:58:05+00:00

[ Upstream commit 4a74da044ec9ec8679e6beccc4306b936b62873f ] KASAN reports an out of bounds read: BUG: KASAN: slab-out-of-bounds in __kuid_val include/linux/uidgid.h:36 BUG: KASAN: slab-out-of-bounds in uid_eq include/linux/uidgid.h:63 [inline] BUG: KASAN: slab-out-of-bounds in key_task_permission+0x394/0x410 security/keys/permission.c:54 Read of size 4 at addr ffff88813c3ab618 by task stress-ng/4362 CPU: 2 PID: 4362 Comm: stress-ng Not tainted 5.10.0-14930-gafbffd6c3ede #15 Call Trace: __dump_stack lib/dump_stack.c:82 [inline] dump_stack+0x107/0x167 lib/dump_stack.c:123 print_address_description.constprop.0+0x19/0x170 mm/kasan/report.c:400 __kasan_report.cold+0x6c/0x84 mm/kasan/report.c:560 kasan_report+0x3a/0x50 mm/kasan/report.c:585 __kuid_val include/linux/uidgid.h:36 [inline] uid_eq include/linux/uidgid.h:63 [inline] key_task_permission+0x394/0x410 security/keys/permission.c:54 search_nested_keyrings+0x90e/0xe90 security/keys/keyring.c:793 This issue was also reported by syzbot. It can be reproduced by following these steps(more details [1]): 1. Obtain more than 32 inputs that have similar hashes, which ends with the pattern '0xxxxxxxe6'. 2. Reboot and add the keys obtained in step 1. The reproducer demonstrates how this issue happened: 1. In the search_nested_keyrings function, when it iterates through the slots in a node(below tag ascend_to_node), if the slot pointer is meta and node->back_pointer != NULL(it means a root), it will proceed to descend_to_node. However, there is an exception. If node is the root, and one of the slots points to a shortcut, it will be treated as a keyring. 2. Whether the ptr is keyring decided by keyring_ptr_is_keyring function. However, KEYRING_PTR_SUBTYPE is 0x2UL, the same as ASSOC_ARRAY_PTR_SUBTYPE_MASK. 3. When 32 keys with the similar hashes are added to the tree, the ROOT has keys with hashes that are not similar (e.g. slot 0) and it splits NODE A without using a shortcut. When NODE A is filled with keys that all hashes are xxe6, the keys are similar, NODE A will split with a shortcut. Finally, it forms the tree as shown below, where slot 6 points to a shortcut. NODE A +------>+---+ ROOT | | 0 | xxe6 +---+ | +---+ xxxx | 0 | shortcut : : xxe6 +---+ | +---+ xxe6 : : | | | xxe6 +---+ | +---+ | 6 |---+ : : xxe6 +---+ +---+ xxe6 : : | f | xxe6 +---+ +---+ xxe6 | f | +---+ 4. As mentioned above, If a slot(slot 6) of the root points to a shortcut, it may be mistakenly transferred to a key*, leading to a read out-of-bounds read. To fix this issue, one should jump to descend_to_node if the ptr is a shortcut, regardless of whether the node is root or not. [1] https://lore.kernel.org/linux-kernel/1cfa878e-8c7b-4570-8606-21daf5e13ce7@huaweicloud.com/ [jarkko: tweaked the commit message a bit to have an appropriate closes tag.] Fixes: b2a4df200d57 ("KEYS: Expand the capacity of a keyring") Reported-by: syzbot+5b415c07907a2990d1a3@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/000000000000cbb7860611f61147@google.com/T/ Signed-off-by: Chen Ridong Reviewed-by: Jarkko Sakkinen Signed-off-by: Jarkko Sakkinen Signed-off-by: Sasha Levin

KEYS: Don't write out to userspace while holding key semaphore

2020-04-23T08:30:24+00:00

commit d3ec10aa95819bff18a0d936b18884c7816d0914 upstream. 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 all the relevant read methods as well as additional changes to not use any userspace write helpers. That is, 1) The put_user() call is replaced by a direct copy. 2) The copy_to_user() call is replaced by memcpy(). 3) All the fault handling code is removed. Compiling on a x86-64 system, the size of the rxrpc_read() function is reduced from 3795 bytes to 2384 bytes with this patch. Fixes: ^1da177e4c3f4 ("Linux-2.6.12-rc2") Reviewed-by: Jarkko Sakkinen Signed-off-by: Waiman Long Signed-off-by: David Howells Signed-off-by: Greg Kroah-Hartman

KEYS: always initialize keyring_index_key::desc_len

2019-02-27T09:09:00+00:00

commit ede0fa98a900e657d1fcd80b50920efc896c1a4c upstream. syzbot hit the 'BUG_ON(index_key->desc_len == 0);' in __key_link_begin() called from construct_alloc_key() during sys_request_key(), because the length of the key description was never calculated. The problem is that we rely on ->desc_len being initialized by search_process_keyrings(), specifically by search_nested_keyrings(). But, if the process isn't subscribed to any keyrings that never happens. Fix it by always initializing keyring_index_key::desc_len as soon as the description is set, like we already do in some places. The following program reproduces the BUG_ON() when it's run as root and no session keyring has been installed. If it doesn't work, try removing pam_keyinit.so from /etc/pam.d/login and rebooting. #include #include #include int main(void) { int id = add_key("keyring", "syz", NULL, 0, KEY_SPEC_USER_KEYRING); keyctl_setperm(id, KEY_OTH_WRITE); setreuid(5000, 5000); request_key("user", "desc", "", id); } Reported-by: syzbot+ec24e95ea483de0a24da@syzkaller.appspotmail.com Fixes: b2a4df200d57 ("KEYS: Expand the capacity of a keyring") Signed-off-by: Eric Biggers Signed-off-by: David Howells Cc: stable@vger.kernel.org Signed-off-by: James Morris Signed-off-by: Greg Kroah-Hartman

keyring: Remove now-redundant smp_read_barrier_depends()

2017-12-04T18:53:14+00:00

Now that the associative-array library properly heads dependency chains, the various smp_read_barrier_depends() calls in security/keys/keyring.c are no longer needed. This commit therefore removes them. Signed-off-by: Paul E. McKenney Cc: David Howells Cc: "Serge E. Hallyn" Cc: Cc: Reviewed-by: James Morris

security: keys: Replace time_t/timespec with time64_t

2017-11-15T16:38:45+00:00

The 'struct key' will use 'time_t' which we try to remove in the kernel, since 'time_t' is not year 2038 safe on 32bit systems. Also the 'struct keyring_search_context' will use 'timespec' type to record current time, which is also not year 2038 safe on 32bit systems. Thus this patch replaces 'time_t' with 'time64_t' which is year 2038 safe for 'struct key', and replace 'timespec' with 'time64_t' for the 'struct keyring_search_context', since we only look at the the seconds part of 'timespec' variable. Moreover we also change the codes where using the 'time_t' and 'timespec', and we can get current time by ktime_get_real_seconds() instead of current_kernel_time(), and use 'TIME64_MAX' macro to initialize the 'time64_t' type variable. Especially in proc.c file, we have replaced 'unsigned long' and 'timespec' type with 'u64' and 'time64_t' type to save the timeout value, which means user will get one 'u64' type timeout value by issuing proc_keys_show() function. Signed-off-by: Baolin Wang Reviewed-by: Arnd Bergmann Signed-off-by: David Howells Reviewed-by: James Morris

KEYS: return full count in keyring_read() if buffer is too small

2017-11-02T09:58:05+00:00

Commit e645016abc80 ("KEYS: fix writing past end of user-supplied buffer in keyring_read()") made keyring_read() stop corrupting userspace memory when the user-supplied buffer is too small. However it also made the return value in that case be the short buffer size rather than the size required, yet keyctl_read() is actually documented to return the size required. Therefore, switch it over to the documented behavior. Note that for now we continue to have it fill the short buffer, since it did that before (pre-v3.13) and dump_key_tree_aux() in keyutils arguably relies on it. Fixes: e645016abc80 ("KEYS: fix writing past end of user-supplied buffer in keyring_read()") Reported-by: Ben Hutchings Cc: # v3.13+ Signed-off-by: Eric Biggers Signed-off-by: David Howells Reviewed-by: James Morris Signed-off-by: James Morris

KEYS: Load key expiry time atomically in keyring_search_iterator()

2017-10-18T08:12:41+00:00

Similar to the case for key_validate(), we should load the key ->expiry once atomically in keyring_search_iterator(), since it can be changed concurrently with the flags whenever the key semaphore isn't held. Signed-off-by: Eric Biggers Signed-off-by: David Howells

KEYS: Fix race between updating and finding a negative key

2017-10-18T08:12:40+00:00

Consolidate KEY_FLAG_INSTANTIATED, KEY_FLAG_NEGATIVE and the rejection error into one field such that: (1) The instantiation state can be modified/read atomically. (2) The error can be accessed atomically with the state. (3) The error isn't stored unioned with the payload pointers. This deals with the problem that the state is spread over three different objects (two bits and a separate variable) and reading or updating them atomically isn't practical, given that not only can uninstantiated keys change into instantiated or rejected keys, but rejected keys can also turn into instantiated keys - and someone accessing the key might not be using any locking. The main side effect of this problem is that what was held in the payload may change, depending on the state. For instance, you might observe the key to be in the rejected state. You then read the cached error, but if the key semaphore wasn't locked, the key might've become instantiated between the two reads - and you might now have something in hand that isn't actually an error code. The state is now KEY_IS_UNINSTANTIATED, KEY_IS_POSITIVE or a negative error code if the key is negatively instantiated. The key_is_instantiated() function is replaced with key_is_positive() to avoid confusion as negative keys are also 'instantiated'. Additionally, barriering is included: (1) Order payload-set before state-set during instantiation. (2) Order state-read before payload-read when using the key. Further separate barriering is necessary if RCU is being used to access the payload content after reading the payload pointers. Fixes: 146aa8b1453b ("KEYS: Merge the type-specific data with the payload data") Cc: stable@vger.kernel.org # v4.4+ Reported-by: Eric Biggers Signed-off-by: David Howells Reviewed-by: Eric Biggers

KEYS: prevent creating a different user's keyrings

2017-09-25T14:19:57+00:00

It was possible for an unprivileged user to create the user and user session keyrings for another user. For example: sudo -u '#3000' sh -c 'keyctl add keyring _uid.4000 "" @u keyctl add keyring _uid_ses.4000 "" @u sleep 15' & sleep 1 sudo -u '#4000' keyctl describe @u sudo -u '#4000' keyctl describe @us This is problematic because these "fake" keyrings won't have the right permissions. In particular, the user who created them first will own them and will have full access to them via the possessor permissions, which can be used to compromise the security of a user's keys: -4: alswrv-----v------------ 3000 0 keyring: _uid.4000 -5: alswrv-----v------------ 3000 0 keyring: _uid_ses.4000 Fix it by marking user and user session keyrings with a flag KEY_FLAG_UID_KEYRING. Then, when searching for a user or user session keyring by name, skip all keyrings that don't have the flag set. Fixes: 69664cf16af4 ("keys: don't generate user and user session keyrings unless they're accessed") Cc: [v2.6.26+] Signed-off-by: Eric Biggers Signed-off-by: David Howells

KEYS: fix writing past end of user-supplied buffer in keyring_read()

2017-09-25T14:19:57+00:00

Userspace can call keyctl_read() on a keyring to get the list of IDs of keys in the keyring. But if the user-supplied buffer is too small, the kernel would write the full list anyway --- which will corrupt whatever userspace memory happened to be past the end of the buffer. Fix it by only filling the space that is available. Fixes: b2a4df200d57 ("KEYS: Expand the capacity of a keyring") Cc: [v3.13+] Signed-off-by: Eric Biggers Signed-off-by: David Howells