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Message-ID: <eef47f37-6d96-4c60-a00b-e96e6025ef43@huawei.com>
Date: Thu, 26 Sep 2024 19:20:25 +0800
From: chenridong <chenridong@...wei.com>
To: Jarkko Sakkinen <jarkko@...nel.org>, Chen Ridong
<chenridong@...weicloud.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>, <James.Bottomley@...senPartnership.com>,
<roberto.sassu@...weicloud.com>
Subject: Re: [PATCH] security/keys: fix slab-out-of-bounds in
key_task_permission
On 2024/9/26 17:54, Jarkko Sakkinen wrote:
> On Thu Sep 26, 2024 at 11:55 AM EEST, Jarkko Sakkinen wrote:
>> On Thu Sep 26, 2024 at 11:53 AM EEST, Jarkko Sakkinen wrote:
>>> On Thu Sep 26, 2024 at 6:48 AM EEST, Chen Ridong wrote:
>>>>
>>>> On 2024/9/19 4:57, Jarkko Sakkinen wrote:
>>>>> On Wed Sep 18, 2024 at 10:30 AM EEST, Chen Ridong wrote:
>>>>>>
>>>>>>
>>>>>> On 2024/9/15 21:59, Jarkko Sakkinen wrote:
>>>>>>> On Sun Sep 15, 2024 at 3:55 AM EEST, Chen Ridong wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> 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?
>>>>>>>
>>>>>>> I only comment new patch versions so not giving any promises but I can
>>>>>>> say that it is I think definitely in the correct direction :-)
>>>>>>>
>>>>>>> BR, Jarkko
>>>>>>
>>>>>> Hello, Jarkko. I have reproduced this issue. It can be reproduced by
>>>>>> following these steps:
>>>>>>
>>>>>> 1. Add the helper patch.
>>>>>>
>>>>>> @@ -205,6 +205,9 @@ static void hash_key_type_and_desc(struct
>>>>>> keyring_index_key *index_key)
>>>>>> else if (index_key->type == &key_type_keyring && (hash &
>>>>>> fan_mask) != 0)
>>>>>> hash = (hash + (hash << level_shift)) & ~fan_mask;
>>>>>> index_key->hash = hash;
>>>>>> + if ((index_key->hash & 0xff) == 0xe6) {
>>>>>> + pr_err("hash_key_type_and_desc: type %s %s
>>>>>> 0x%x\n", index_key->type->name, index_key->description, index_key->hash);
>>>>>> + }
>>>>>> }
>>>>>>
>>>>>> 2. Pick up the inputs whose hash is xxe6 using the following cmd. If a
>>>>>> key's hash is xxe6, it will be printed.
>>>>>>
>>>>>> for ((i=0; i<=10000; i++)); do ./test_key user user$i "Some payload"; done
>>>>>>
>>>>>> You have complile test_key whith following code.
>>>>>>
>>>>>> #include <sys/types.h>
>>>>>> #include <keyutils.h>
>>>>>> #include <stdint.h>
>>>>>> #include <stdio.h>
>>>>>> #include <stdlib.h>
>>>>>> #include <string.h>
>>>>>>
>>>>>> int
>>>>>> main(int argc, char *argv[])
>>>>>> {
>>>>>> key_serial_t key;
>>>>>>
>>>>>> if (argc != 4) {
>>>>>> fprintf(stderr, "Usage: %s type description payload\n",
>>>>>> argv[0]);
>>>>>> exit(EXIT_FAILURE);
>>>>>> }
>>>>>>
>>>>>> key = add_key(argv[1], argv[2], argv[3], strlen(argv[3]),
>>>>>> KEY_SPEC_SESSION_KEYRING);
>>>>>> if (key == -1) {
>>>>>> perror("add_key");
>>>>>> exit(EXIT_FAILURE);
>>>>>> }
>>>>>>
>>>>>> printf("Key ID is %jx\n", (uintmax_t) key);
>>>>>>
>>>>>> exit(EXIT_SUCCESS);
>>>>>> }
>>>>>>
>>>>>>
>>>>>> 3. Have more than 32 inputs now. their hashes are xxe6.
>>>>>> eg.
>>>>>> hash_key_type_and_desc: type user user438 0xe3033fe6
>>>>>> hash_key_type_and_desc: type user user526 0xeb7eade6
>>>>>> ...
>>>>>> hash_key_type_and_desc: type user user9955 0x44bc99e6
>>>>>>
>>>>>> 4. Reboot and add the keys obtained from step 3.
>>>>>> When adding keys to the ROOT that their hashes are all xxe6, and up to
>>>>>> 16, the ROOT has keys with hashes that are not xxe6 (e.g., slot 0), so
>>>>>> the keys are dissimilar. The ROOT will then split NODE A without using a
>>>>>> shortcut. When NODE A is filled with keys that have hashes of xxe6, the
>>>>>> keys are similar. NODE A will split with a shortcut.
>>>>>>
>>>>>> As my analysis, if a slot of the root is a shortcut(slot 6), it may be
>>>>>> mistakenly be transferred to a key*, leading to an read out-of-bounds read.
>>>>>>
>>>>>> NODE A
>>>>>> +------>+---+
>>>>>> ROOT | | 0 | xxe6
>>>>>> +---+ | +---+
>>>>>> xxxx | 0 | shortcut : : xxe6
>>>>>> +---+ | +---+
>>>>>> xxe6 : : | | | xxe6
>>>>>> +---+ | +---+
>>>>>> | 6 |---+ : : xxe6
>>>>>> +---+ +---+
>>>>>> xxe6 : : | f | xxe6
>>>>>> +---+ +---+
>>>>>> xxe6 | f |
>>>>>> +---+
>>>>>>
>>>>>> 5. cat /proc/keys. and the issue is reproduced.
>>>>>
>>>>> Hi, I'll try to run through your procedure next week and give my comments.
>>>>> Thanks for doing this.
>>>>>
>>>>> BR, Jarkko
>>>>
>>>> Hi, Jarkko, have you run these procedure?
>>>> I have tested this patch with LTP and a pressure test(stress-ng --key),
>>>> and this patch have fixed this issue. Additionally, no new bugs have
>>>> been found so far.
>>>>
>>>> I am looking forward to your reply.
>>>>
>>>> Best regards,
>>>> Ridong
>>>
>>> Nope because we are apparently stuck with release critical bug:
>>>
>>> https://lore.kernel.org/linux-integrity/D4EPMF7G3E05.1VHS9CVG3DZDE@kernel.org/T/#t
>>>
>>> Might take several weeks before I look into this.
>>
>> I was expecting to send a PR early this week since the patch set
>> addresses the issue so thus wrong estimation.
>
> I asked David if he could look into this.
>
> BR, Jarkko
Thank you very much.
Best regards,
Ridong
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