Re: [PATCH v8 2/2] firmware_loader: fix use-after-free in firmware_fallback_sysfs

[Shuah Khan]

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@xxxxxxxxxxxxxxxxxxxxxxxxx
> Tested-by: syzbot+de271708674e2093097b@xxxxxxxxxxxxxxxxxxxxxxxxx
> Acked-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> Signed-off-by: Anirudh Rayabharam <mail@xxxxxxxxxxxxx>
> ---
>   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@xxxxxxxxxxxxxxxxxxx>

thanks,
-- Shuah