linux-kernel - Re: [PATCH v7 2/2] firmware_loader: fix use-after-free in firmware_fallback

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Message-ID: <20210726182721.3no7ql73ggttdiyx@garbanzo>
Date:   Mon, 26 Jul 2021 11:27:21 -0700
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Anirudh Rayabharam <mail@...rudhrb.com>
Cc:     gregkh@...uxfoundation.org, rafael@...nel.org,
        skhan@...uxfoundation.org, linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        syzbot+de271708674e2093097b@...kaller.appspotmail.com
Subject: Re: [PATCH v7 2/2] firmware_loader: fix use-after-free in
 firmware_fallback_sysfs

On Sat, Jul 24, 2021 at 05:41:34PM +0530, Anirudh Rayabharam wrote:
> This use-after-free happens when a fw_priv object has been freed but
> hasn't been removed from the pending list (pending_fw_head). The next
> time fw_load_sysfs_fallback tries to insert into the list, it ends up
> accessing the pending_list member of the previoiusly freed fw_priv.
> 
> The root cause here is that all code paths that abort the fw load
> don't delete it from the pending list. For example:
> 
> 	_request_firmware()
> 	  -> fw_abort_batch_reqs()
> 	      -> fw_state_aborted()
> 
> To fix this, delete the fw_priv from the list in __fw_set_state() if
> the new state is DONE or ABORTED. This way, all aborts will remove
> the fw_priv from the list. Accordingly, remove calls to list_del_init
> that were being made before calling fw_state_(aborted|done).
> 
> Also, in fw_load_sysfs_fallback, don't add the fw_priv to the pending
> list if it is already aborted. Instead, just jump out and return early.
> 
> Fixes: bcfbd3523f3c ("firmware: fix a double abort case with fw_load_sysfs_fallback")
> Reported-by: syzbot+de271708674e2093097b@...kaller.appspotmail.com
> Tested-by: syzbot+de271708674e2093097b@...kaller.appspotmail.com

Curious, how do you get syzbot to test this, I mean your custom tree?

> Signed-off-by: Anirudh Rayabharam <mail@...rudhrb.com>

With the changes Shua requested being made:

Acked-by: Luis Chamberlain <mcgrof@...nel.org>

  Luis