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Message-Id: <D4GDQXEN0RKN.L4Q48E96DC8H@kernel.org>
Date: Thu, 26 Sep 2024 20:08:47 +0300
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "chenridong" <chenridong@...wei.com>, "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 Thu Sep 26, 2024 at 2:20 PM EEST, chenridong wrote:
>
>
> 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.
Further, I'm switching jobs. Tomorrow is my last day in the current
job and next week starting a new job so given all these circumastances
I rather look into this properly hopefully latest after my rc2 PR is
out, rather than rushing.
In a normal status quo situation this would not be such a huge issue.
Similarly, for the performance bug I want to review James' comments
etc with time and bake v6 that hopefully satisfies all the
stateholders.
So thank you for understanding, and I appreciate the work you've done
on this. I.e. not ignoring this :-)
BR, Jarkko
BR, Jarkko
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