From 20c40794eb85ea29852d7bc37c55713802a543d6 Mon Sep 17 00:00:00 2001
From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Date: Fri, 12 Feb 2021 22:26:58 +0300
Subject: [PATCH] misc: fastrpc: restrict user apps from sending kernel RPC
messages
Verify that user applications are not using the kernel RPC message
handle to restrict them from directly attaching to guest OS on the
remote subsystem. This is a port of CVE-2019-2308 fix.
Fixes: c68cfb718c8f ("misc: fastrpc: Add support for context Invoke method")
Cc: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Cc: Jonathan Marek <jonathan@marek.ca>
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20210212192658.3476137-1-dmitry.baryshkov@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/misc/fastrpc.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index f12e909034ac0..beda610e6b30d 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -950,6 +950,11 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl, u32 kernel,
if (!fl->cctx->rpdev)
return -EPIPE;
+ if (handle == FASTRPC_INIT_HANDLE && !kernel) {
+ dev_warn_ratelimited(fl->sctx->dev, "user app trying to send a kernel RPC message (%d)\n", handle);
+ return -EPERM;
+ }
+
ctx = fastrpc_context_alloc(fl, kernel, sc, args);
if (IS_ERR(ctx))
return PTR_ERR(ctx);
--
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