linux-kernel - Re: [PATCH RESEND] mac802154: Fix uninit-value access in ieee802154_hdr_push

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Message-ID: <95702cc6-187e-4ce9-b9b8-6320c9ddc7da@fintech.ru>
Date: Tue, 6 Feb 2024 10:15:37 -0800
From: Nikita Zhandarovich <n.zhandarovich@...tech.ru>
To: Alexander Aring <aahringo@...hat.com>
CC: Zhang Shurong <zhang_shurong@...mail.com>, <alex.aring@...il.com>,
	<stefan@...enfreihafen.org>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <pabeni@...hat.com>, <linux-wpan@...r.kernel.org>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<harperchen1110@...il.com>
Subject: Re: [PATCH RESEND] mac802154: Fix uninit-value access in
 ieee802154_hdr_push_sechdr

Hi,

On 2/5/24 11:49, Alexander Aring wrote:
> Hi,
> 
> On Thu, Jan 18, 2024 at 8:00 AM Nikita Zhandarovich
> <n.zhandarovich@...tech.ru> wrote:
> ...
>>
>> I was curious whether a smaller change would suffice since I might be
>> too green to see the full picture here.
>>
>> In all honesty I am failing to see how exactly it happens that cb->secen
>> == 1 and cb->secen_override == 0 (which is exactly what occurs during
>> this error repro) at the start of mac802154_set_header_security().
>> Since there is a check in mac802154_set_header_security()
>>
>>         if (!params.enabled && cb->secen_override && cb->secen)
>>
>> maybe we take off 'cb->secen_override' part of the condition? That way
>> we catch the case when security is supposedly enabled without parameters
>> being available (not enabled) and return with error. Or is this approach
>> too lazy?
> 
> I need to see the full patch for this. In my opinion there are two patches here:
> 

Alex, I am gonna try to test your version and send out patches before
the end of week, thank you for reminding me.

> 1. fix uninit values
> 2. return an error with some mismatched security parameters. (I think
> this is where your approach comes in place)
> 
> The 1. case is what syzbot is complaining about and in my opinion easy
> to fix at [0] to init some more default values of "struct dgram_sock"
> [1].

However, if I may, I am still worried that initing stuff in [0] won't
help much. They way I see it, there are mismatched sec. parameters that
lead to the actual uninit issue, but are not victim of it themselves.

Specifically, once we enter mac802154_set_header_security() all fields
of 'cb' have values (albeit a possibly wrong combo of them), values
copied from 'ro' seemingly w/o a hitch; the function ends early (cause
of mismatch); we end up NOT filling values in ieee802154_hdr *hdr, at
the very least these:

	hdr->sec.level = level;
	hdr->sec.key_id_mode = params.out_key.mode;

Then we are back in ieee802154_header_create():
ieee802154_header_create -> ieee802154_hdr_push ->
ieee802154_hdr_push_sechdr, where we finally access aforementioned
values despite putting nothing in them.

In other words, I am unsure that mismatch in sec. parameters (cb->secen,
params.enabled etc.), which leads to uninit issues in hdr->sec.XXX
fields, is itself caused by the uninit values in dgram_sock (since KMSAN
should have caught it earlier). But if you are certain, I don't mind
taking on the patches you suggested.

> 
> Then 2. can be fixed afterwards.
> 
> - Alex
> 
> [0] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/net/ieee802154/socket.c#n474
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/net/ieee802154/socket.c#n435
> 

Thank you for your patience,
Nikita