linux-kernel - Re: [PATCH] security/keys: fix slab-out-of-bounds in key_task

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4079d020-edcc-4e27-9815-580f83a6c0ca@huaweicloud.com>
Date: Sun, 15 Sep 2024 08:55:07 +0800
From: Chen Ridong <chenridong@...weicloud.com>
To: Jarkko Sakkinen <jarkko@...nel.org>, Chen Ridong <chenridong@...wei.com>,
 dhowells@...hat.com, paul@...l-moore.com, jmorris@...ei.org, serge@...lyn.com
Cc: keyrings@...r.kernel.org, linux-security-module@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] security/keys: fix slab-out-of-bounds in
 key_task_permission



On 2024/9/14 19:33, Jarkko Sakkinen wrote:
> On Fri Sep 13, 2024 at 10:09 AM EEST, Chen Ridong wrote:
>> We meet the same issue with the LINK, which reads memory out of bounds:
> 
> Nit: don't use "we" anywhere".
> 
> Tbh, I really don't understand the sentence above. I don't what
> "the same issue with the LINK" really is.
> 

Hello, Jarkko.
I apologize for any confusion caused.

I've encountered a bug reported by syzkaller. I also found the same bug 
reported at this LINK: 
https://syzkaller.appspot.com/bug?id=68a5e206c2a8e08d317eb83f05610c0484ad10b9.

>> 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
>>   keyring_search_rcu+0x1b6/0x310 security/keys/keyring.c:922
>>   search_cred_keyrings_rcu+0x111/0x2e0 security/keys/process_keys.c:459
>>   search_process_keyrings_rcu+0x1d/0x310 security/keys/process_keys.c:544
>>   lookup_user_key+0x782/0x12e0 security/keys/process_keys.c:762
>>   keyctl_invalidate_key+0x20/0x190 security/keys/keyctl.c:434
>>   __do_sys_keyctl security/keys/keyctl.c:1978 [inline]
>>   __se_sys_keyctl+0x1de/0x5b0 security/keys/keyctl.c:1880
>>   do_syscall_64+0x30/0x40 arch/x86/entry/common.c:46
>>   entry_SYSCALL_64_after_hwframe+0x67/0xd1
>>
>> However, we can't reproduce this issue.
> 
> "The issue cannot be easily reproduced but by analyzing the code
> it can be broken into following steps:"

Thank you for your correction.
Does this patch address the issue correctly? Is this patch acceptable?

Best regard,
Ridong

> 
>> After our analysis, it can make this issue by following steps.
>> 1.As syzkaller reported, the memory is allocated for struct
>>    assoc_array_shortcut in the assoc_array_insert_into_terminal_node
>>    functions.
>> 2.In the search_nested_keyrings, when we go through the slots in a node,
>>    (bellow tag ascend_to_node), and the slot ptr is meta and
>>    node->back_pointer != NULL, we 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.
>> 3.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,
>> 4.As mentioned above, If a slot of the root is a shortcut, it may be
>>    mistakenly be transferred to a key*, leading to an read out-of-bounds
>>    read.
>>
>> To fix this issue, one should jump to descend_to_node if the pointer is a
>> shortcut.
>>
>> Link: https://syzkaller.appspot.com/bug?id=68a5e206c2a8e08d317eb83f05610c0484ad10b9
>> Fixes: b2a4df200d57 ("KEYS: Expand the capacity of a keyring")
>> Signed-off-by: Chen Ridong <chenridong@...wei.com>
>> ---
>>   security/keys/keyring.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/security/keys/keyring.c b/security/keys/keyring.c
>> index 4448758f643a..7958486ac834 100644
>> --- a/security/keys/keyring.c
>> +++ b/security/keys/keyring.c
>> @@ -772,7 +772,9 @@ static bool search_nested_keyrings(struct key *keyring,
>>   	for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
>>   		ptr = READ_ONCE(node->slots[slot]);
>>   
>> -		if (assoc_array_ptr_is_meta(ptr) && node->back_pointer)
>> +		if ((assoc_array_ptr_is_meta(ptr) && node->back_pointer) ||
>> +		    (assoc_array_ptr_is_meta(ptr) &&
>> +		     assoc_array_ptr_is_shortcut(ptr)))
>>   			goto descend_to_node;
>>   
>>   		if (!keyring_ptr_is_keyring(ptr))
> 
> 
> BR, Jarkko