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From: Anirudh Rayabharam <mail@anirudhrb.com>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: gregkh@linuxfoundation.org, rafael@kernel.org,
	skhan@linuxfoundation.org, linux-kernel@vger.kernel.org,
	linux-kernel-mentees@lists.linuxfoundation.org,
	syzbot+de271708674e2093097b@syzkaller.appspotmail.com
Subject: Re: [PATCH v7 2/2] firmware_loader: fix use-after-free in firmware_fallback_sysfs
Date: Tue, 27 Jul 2021 18:27:06 +0530	[thread overview]
Message-ID: <YQACopP/tRsLFQVJ@anirudhrb.com> (raw)
In-Reply-To: <20210726182721.3no7ql73ggttdiyx@garbanzo>

On Mon, Jul 26, 2021 at 11:27:21AM -0700, Luis Chamberlain wrote:
> 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@syzkaller.appspotmail.com
> > Tested-by: syzbot+de271708674e2093097b@syzkaller.appspotmail.com
> 
> Curious, how do you get syzbot to test this, I mean your custom tree?

Don't need a custom tree. You can send syzbot the git url of an existing
tree (such as linux-next or Linus' tree) and a patch to apply on that
tree before testing. This is documented here:

https://github.com/google/syzkaller/blob/master/docs/syzbot.md#testing-patches

Of course, using a custom tree is also possible.

> 
> > Signed-off-by: Anirudh Rayabharam <mail@anirudhrb.com>
> 
> With the changes Shua requested being made:

I'll implement Shua's suggestions and send a new version.

Thanks!

	- Anirudh.

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

      reply	other threads:[~2021-07-27 12:57 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-24 12:11 [PATCH v7 0/2] firmware_loader: fix uaf " Anirudh Rayabharam
2021-07-24 12:11 ` [PATCH v7 1/2] firmware_loader: use -ETIMEDOUT instead of -EAGAIN in fw_load_sysfs_fallback Anirudh Rayabharam
2021-07-26 16:56   ` Shuah Khan
2021-07-26 18:07   ` Luis Chamberlain
2021-07-24 12:11 ` [PATCH v7 2/2] firmware_loader: fix use-after-free in firmware_fallback_sysfs Anirudh Rayabharam
2021-07-26 17:22   ` Shuah Khan
2021-07-26 18:27   ` Luis Chamberlain
2021-07-27 12:57     ` Anirudh Rayabharam [this message]

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