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From:   sangsup lee <k1rh4.lee@gmail.com>
Date:   Thu, 27 Apr 2023 18:29:16 +0900
Message-ID: <CAJkuJRjFCXkS+osc8ezpAw0E2W7WMAJnnxMt_cs4deqgm5OzHw@mail.gmail.com>
Subject: Re: [PATCH v2] misc: fastrpc: Fix a Use after-free-bug by race condition
To:     Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc:     Amol Maheshwari <amahesh@qti.qualcomm.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org
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Is there any comment for this issue?
(reference: https://www.spinics.net/lists/kernel/msg4731408.html)


2023=EB=85=84 3=EC=9B=94 23=EC=9D=BC (=EB=AA=A9) =EC=98=A4=EC=A0=84 10:37, =
Sangsup Lee <k1rh4.lee@gmail.com>=EB=8B=98=EC=9D=B4 =EC=9E=91=EC=84=B1:
>
> From: Sangsup lee <k1rh4.lee@gmail.com>
>
> This patch adds mutex_lock for fixing an Use-after-free bug.
> fastrpc_req_munmap_impl can be called concurrently in multi-threded envir=
onments.
> The buf which is allocated by list_for_each_safe can be used after anothe=
r thread frees it.
>
> Signed-off-by: Sangsup lee <k1rh4.lee@gmail.com>
> ---
>  V1 -> V2: moving the locking to ioctl.
>
>  drivers/misc/fastrpc.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 93ebd174d848..aa1cf0e9f4ed 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -1901,7 +1901,9 @@ static long fastrpc_device_ioctl(struct file *file,=
 unsigned int cmd,
>                 err =3D fastrpc_req_mmap(fl, argp);
>                 break;
>         case FASTRPC_IOCTL_MUNMAP:
> +               mutex_lock(&fl->mutex);
>                 err =3D fastrpc_req_munmap(fl, argp);
> +               mutex_unlock(&fl->mutex);
>                 break;
>         case FASTRPC_IOCTL_MEM_MAP:
>                 err =3D fastrpc_req_mem_map(fl, argp);
> --
> 2.25.1
>