linux-kernel - [PATCH] soc: ti: wkup_m3_ipc: Fix race condition with rproc

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Date:   Wed, 11 Dec 2019 22:03:14 -0600
From:   Dave Gerlach <d-gerlach@...com>
To:     Tony Lindgren <tony@...mide.com>,
        Santosh Shilimkar <ssantosh@...nel.org>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
        Dave Gerlach <d-gerlach@...com>, Suman Anna <s-anna@...com>
Subject: [PATCH] soc: ti: wkup_m3_ipc: Fix race condition with rproc_boot

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@...com>
Signed-off-by: Dave Gerlach <d-gerlach@...com>
---
 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 378369d9364a..e9ece45d7a33 100644
--- a/drivers/soc/ti/wkup_m3_ipc.c
+++ b/drivers/soc/ti/wkup_m3_ipc.c
@@ -419,6 +419,8 @@ 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);
 }
@@ -505,8 +507,6 @@ 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