Re: [PATCH] rpmsg: glink: Fix buffer overflow

From: Bjorn Andersson <quic_bjorande@quicinc.com>
To: Hardevsinh Palaniya <hardevsinh.palaniya@siliconsignals.io>
Cc: "agross@kernel.org" <agross@kernel.org>,
	"andersson@kernel.org" <andersson@kernel.org>,
	Konrad Dybcio <konrad.dybcio@linaro.org>,
	Mathieu Poirier <mathieu.poirier@linaro.org>,
	"linux-arm-msm@vger.kernel.org" <linux-arm-msm@vger.kernel.org>,
	"linux-remoteproc@vger.kernel.org"
	<linux-remoteproc@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] rpmsg: glink: Fix buffer overflow
Date: Wed, 13 Dec 2023 14:58:38 -0800	[thread overview]
Message-ID: <20231213225838.GQ1766637@hu-bjorande-lv.qualcomm.com> (raw)
In-Reply-To: <MA0PR01MB7145C9A06689F2C5C43A3876FF8DA@MA0PR01MB7145.INDPRD01.PROD.OUTLOOK.COM>

On Wed, Dec 13, 2023 at 03:15:15PM +0000, Hardevsinh Palaniya wrote:
>    Hello [1]@Bjorn Andersson,

Please use appropriate mail list etiquette, and avoid HTML and
top-posting in your responses.

> 
>    "strscpy_pad" itself takes care of null-terminated strings. So, there
>    will be no leak.

Your strscpy_pad() will NUL-terminate and zero-pad up to 32 bytes.
Following this the next line will write strlen(name) + sizeof(hdr) bytes
to the FIFO.

So if strlen(name) >= 32 you will read beyond the end of the zero-padded
string.

Regards,
Bjorn

>      __________________________________________________________________
> 
>    From: Bjorn Andersson <quic_bjorande@quicinc.com>
>    Sent: Tuesday, December 12, 2023 12:10 AM
>    To: Hardevsinh Palaniya <hardevsinh.palaniya@siliconsignals.io>
>    Cc: agross@kernel.org <agross@kernel.org>; andersson@kernel.org
>    <andersson@kernel.org>; Konrad Dybcio <konrad.dybcio@linaro.org>;
>    Mathieu Poirier <mathieu.poirier@linaro.org>;
>    linux-arm-msm@vger.kernel.org <linux-arm-msm@vger.kernel.org>;
>    linux-remoteproc@vger.kernel.org <linux-remoteproc@vger.kernel.org>;
>    linux-kernel@vger.kernel.org <linux-kernel@vger.kernel.org>
>    Subject: Re: [PATCH] rpmsg: glink: Fix buffer overflow
> 
>    On Mon, Dec 11, 2023 at 09:32:20PM +0530, Hardevsinh Palaniya wrote:
>    > In qcom_glink_send_open_req() remove error: strcpy() 'channel->name'
>    > too large for 'req.name' (1010102 vs 32)
>    >
>    As far as I can tell, channel->name comes from the struct
>    rpmsg_channel_info->name, which is a 32-byte array, and all code paths
>    I
>    can find either uses strscpy() or explicitly NUL-terminates this
>    string.
>    I'm curious to know which path took us here.
>    > Signed-off-by: Hardevsinh Palaniya
>    <hardevsinh.palaniya@siliconsignals.io>
>    >
>    > diff --git a/drivers/rpmsg/qcom_glink_native.c
>    b/drivers/rpmsg/qcom_glink_native.c
>    > index 82d460ff4777..2d6a592e1c72 100644
>    > --- a/drivers/rpmsg/qcom_glink_native.c
>    > +++ b/drivers/rpmsg/qcom_glink_native.c
>    > @@ -479,7 +479,7 @@ static int qcom_glink_send_open_req(struct
>    qcom_glink *glink,
>    >        req.msg.cmd = cpu_to_le16(GLINK_CMD_OPEN);
>    >        req.msg.param1 = cpu_to_le16(channel->lcid);
>    >        req.msg.param2 = cpu_to_le32(name_len);
>    > -     strcpy(req.name, channel->name);
>    > +     strscpy_pad(req.name, channel->name, sizeof(req.name));
>    I think this patch is incomplete. While it makes sure we don't
>    overwrite
>    the stack. name_len is strlen(channel->name) + 1 and the amount of data
>    sent out is based on name_len.
>    As such, if you can get here with a @name of arbitrary length, then you
>    can control how much of the stack we're going to now leak to the
>    recipient.
>    Regards,
>    Bjorn
>    >
>    >        ret = qcom_glink_tx(glink, &req, req_len, NULL, 0, true);
>    >        if (ret)
>    > --
>    > 2.25.1
>    >
>    >
> 
> References
> 
>    1. mailto:quic_bjorande@quicinc.com