linux-kernel - Re: [PATCH v8 2/2] firmware_loader: fix use-after-free in firmware_fallback

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Message-ID: <a3c433b2-3bda-67cc-1ec3-220e4530a12a@linuxfoundation.org>
Date:   Wed, 28 Jul 2021 10:37:38 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Anirudh Rayabharam <mail@...rudhrb.com>, mcgrof@...nel.org,
        gregkh@...uxfoundation.org, rafael@...nel.org
Cc:     linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        syzbot+de271708674e2093097b@...kaller.appspotmail.com,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v8 2/2] firmware_loader: fix use-after-free in
 firmware_fallback_sysfs

On 7/28/21 2:51 AM, 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 previously 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
> Acked-by: Luis Chamberlain <mcgrof@...nel.org>
> Signed-off-by: Anirudh Rayabharam <mail@...rudhrb.com>
> ---
>   drivers/base/firmware_loader/fallback.c | 12 ++++++++----
>   drivers/base/firmware_loader/firmware.h | 10 +++++++++-
>   drivers/base/firmware_loader/main.c     |  2 ++
>   3 files changed, 19 insertions(+), 5 deletions(-)
> 

Thank you. Looks good.

Reviewed-by: Shuah Khan <skhan@...uxfoundation.org>

thanks,
-- Shuah