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Message-ID: <68b51392-0f93-405f-bcf4-94db22831058@huawei.com>
Date: Tue, 8 Oct 2024 09:40:53 +0800
From: chenridong <chenridong@...wei.com>
To: Jarkko Sakkinen <jarkko@...nel.org>, <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>, <chenridong@...weicloud.com>
Subject: Re: [PATCH] security/keys: fix slab-out-of-bounds in
key_task_permission
On 2024/10/8 7:15, Jarkko Sakkinen wrote:
> Hi,
>
> Revisit...
>
> On Fri, 2024-09-13 at 07:09 +0000, Chen Ridong wrote:
>> We meet the same issue with the LINK, which reads memory out of
>> bounds:
>
> Never ever use pronoun "we" in a commit message in any possible
> sentence. Instead always use passive imperative.
>
> What you probably want to say is:
>
> "KASAN reports an out of bounds read:"
>
> Right?
>
Yes.
>> 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
>
> Snip all below away:
>
>> 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
>
> Remember to cut only the relevant part of the stack trace to make this
> commit message more compact and readable.
>
Thank you, I will do that.
>>
>> However, we can't reproduce this issue.
>> After our analysis, it can make this issue by following steps.
>> 1.As syzkaller reported, the memory is allocated for struct
>
> "1."
>
>> 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.
>
> Delete the whole list and write a description of the problem and why
> your change resolves it.
>
> As per code change, let's layout it something more readable first:
>
> /* Traverse branches into depth: */
> if (assoc_array_ptr_is_meta(ptr)) {
> if (node->back_pointer || assoc_array_ptr_is_shortcut(ptr))
> goto descend_to_node;
> }
>
> So one thing that should be explained just to make the description
> rigid is why 'ptr' is passed to assoc_array_ptr_is_shortcut() and
> not 'node'. I'm actually 100% sure about that part, which kind
> of supports my view here, right? :-)
>
> The first part of the if-statement obviously filters out everything
> that is not root (when it comes to 'node'). Explain the second part.
> At that point it is know that node is a root node, so continue from
> there.
>
> BR, Jarkko
>
Thank you for your patience.
I will update soon.
Best regards,
Ridong
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