linux-kernel - [PATCH AUTOSEL 4.14 05/32] soc: ti: wkup_m3_ipc: Fix race condition with rproc

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Date:   Fri, 24 Jan 2020 09:20:52 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Dave Gerlach <d-gerlach@...com>, Suman Anna <s-anna@...com>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Tony Lindgren <tony@...mide.com>,
        Sasha Levin <sashal@...nel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH AUTOSEL 4.14 05/32] soc: ti: wkup_m3_ipc: Fix race condition with rproc_boot

From: Dave Gerlach <d-gerlach@...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@...com>
Signed-off-by: Dave Gerlach <d-gerlach@...com>
Acked-by: Santosh Shilimkar <ssantosh@...nel.org>
Signed-off-by: Tony Lindgren <tony@...mide.com>
Signed-off-by: Sasha Levin <sashal@...nel.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 369aef5e7228e..651827c6ee6f9 100644
--- a/drivers/soc/ti/wkup_m3_ipc.c
+++ b/drivers/soc/ti/wkup_m3_ipc.c
@@ -375,6 +375,8 @@ 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);
 }
@@ -461,8 +463,6 @@ 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