linux-kernel - [PATCH v3 7/9] misc: fastrpc: Restrict untrusted app to attach to privileged PD

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Date: Thu, 30 May 2024 15:50:25 +0530
From: Ekansh Gupta <quic_ekangupt@...cinc.com>
To: <srinivas.kandagatla@...aro.org>, <linux-arm-msm@...r.kernel.org>
CC: <gregkh@...uxfoundation.org>, <quic_bkumar@...cinc.com>,
        <linux-kernel@...r.kernel.org>, <quic_chennak@...cinc.com>,
        stable
	<stable@...nel.org>
Subject: [PATCH v3 7/9] misc: fastrpc: Restrict untrusted app to attach to privileged PD

Untrusted application with access to only non-secure fastrpc device
node can attach to root_pd or static PDs if it can make the respective
init request. This can cause problems as the untrusted application
can send bad requests to root_pd or static PDs. Add changes to reject
attach to privileged PDs if the request is being made using non-secure
fastrpc device node.

Fixes: 0871561055e6 ("misc: fastrpc: Add support for audiopd")
Cc: stable <stable@...nel.org>
Signed-off-by: Ekansh Gupta <quic_ekangupt@...cinc.com>
---
 drivers/misc/fastrpc.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index d9d9f889e39e..73fa0e536cf9 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -1344,6 +1344,11 @@ static int fastrpc_init_create_static_process(struct fastrpc_user *fl,
 	} inbuf;
 	u32 sc;
 
+	if (!fl->is_secure_dev) {
+		dev_dbg(&fl->cctx->rpdev->dev, "untrusted app trying to attach to privileged DSP PD\n");
+		return -EACCES;
+	}
+
 	args = kcalloc(FASTRPC_CREATE_STATIC_PROCESS_NARGS, sizeof(*args), GFP_KERNEL);
 	if (!args)
 		return -ENOMEM;
@@ -1769,6 +1774,11 @@ static int fastrpc_init_attach(struct fastrpc_user *fl, int pd)
 	int tgid = fl->tgid;
 	u32 sc;
 
+	if (!fl->is_secure_dev) {
+		dev_dbg(&fl->cctx->rpdev->dev, "untrusted app trying to attach to privileged DSP PD\n");
+		return -EACCES;
+	}
+
 	args[0].ptr = (u64)(uintptr_t) &tgid;
 	args[0].length = sizeof(tgid);
 	args[0].fd = -1;
-- 
2.43.0