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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Suman Anna <s-anna@ti.com>,
        Dave Gerlach <d-gerlach@ti.com>,
        Santosh Shilimkar <ssantosh@kernel.org>,
        Tony Lindgren <tony@atomide.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 43/68] soc: ti: wkup_m3_ipc: Fix race condition with rproc_boot
Date:   Mon,  3 Feb 2020 16:19:39 +0000
Message-Id: <20200203161912.034960468@linuxfoundation.org>
In-Reply-To: <20200203161904.705434837@linuxfoundation.org>
References: <20200203161904.705434837@linuxfoundation.org>
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From: Dave Gerlach <d-gerlach@ti.com>

[ Upstream commit 03729cfa0d543bc996bf959e762ec999afc8f3d2 ]

Any user of wkup_m3_ipc calls wkup_m3_ipc_get to get a handle and this
checks the value of the static variable m3_ipc_state to see if the
wkup_m3 is ready. Currently this is populated during probe before
rproc_boot has been called, meaning there is a window of time that
wkup_m3_ipc_get can return a valid handle but the wkup_m3 itself is not
ready, leading to invalid IPC calls to the wkup_m3 and system
instability.

To avoid this, move the population of the m3_ipc_state variable until
after rproc_boot has succeeded to guarantee a valid and usable handle
is always returned.

Reported-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Acked-by: Santosh Shilimkar <ssantosh@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/soc/ti/wkup_m3_ipc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/soc/ti/wkup_m3_ipc.c b/drivers/soc/ti/wkup_m3_ipc.c
index 5bb376009d98b..fc33bfdc957cc 100644
--- a/drivers/soc/ti/wkup_m3_ipc.c
+++ b/drivers/soc/ti/wkup_m3_ipc.c
@@ -377,6 +377,8 @@ static void wkup_m3_rproc_boot_thread(struct wkup_m3_ipc *m3_ipc)
 	ret = rproc_boot(m3_ipc->rproc);
 	if (ret)
 		dev_err(dev, "rproc_boot failed\n");
+	else
+		m3_ipc_state = m3_ipc;
 
 	do_exit(0);
 }
@@ -463,8 +465,6 @@ static int wkup_m3_ipc_probe(struct platform_device *pdev)
 		goto err_put_rproc;
 	}
 
-	m3_ipc_state = m3_ipc;
-
 	return 0;
 
 err_put_rproc:
-- 
2.20.1