linux-kernel - [PATCH] clk: Fix referring to wrong pointer in devm_clk

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Message-Id: <1655946142-1346-1-git-send-email-hayashi.kunihiko@socionext.com>
Date:   Thu, 23 Jun 2022 10:02:22 +0900
From:   Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
To:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
Subject: [PATCH] clk: Fix referring to wrong pointer in devm_clk_release()

At bind phase, __devm_clk_get() calls devres_alloc() to allocate devres,
and dr->data is treated as a variable "state".

At unbind phase, release_nodes() calls devm_clk_release() specified by
devres_alloc().

The argument "res" of devm_clk_release() is dr->data, and this entity is
"state", however in devm_clk_release(), "*res" is treated as "state",
resulting in pointer inconsistency.

Unbinding a driver caused a panic.

    Unable to handle kernel execute from non-executable memory
    at virtual address ffff000100236810
    ...
    pc : 0xffff000100236810
    lr : devm_clk_release+0x6c/0x9c
    ...
    Call trace:
     0xffff000100236810
     release_nodes+0xb0/0x150
     devres_release_all+0x94/0xf8
     device_unbind_cleanup+0x20/0x70
     device_release_driver_internal+0x114/0x1a0
     device_driver_detach+0x20/0x30

Cc: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Fixes: abae8e57e49a ("clk: generalize devm_clk_get() a bit")
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
---
 drivers/clk/clk-devres.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/clk-devres.c b/drivers/clk/clk-devres.c
index 43ccd20e0298..1f37ed7ad395 100644
--- a/drivers/clk/clk-devres.c
+++ b/drivers/clk/clk-devres.c
@@ -11,7 +11,7 @@ struct devm_clk_state {
 
 static void devm_clk_release(struct device *dev, void *res)
 {
-	struct devm_clk_state *state = *(struct devm_clk_state **)res;
+	struct devm_clk_state *state = (struct devm_clk_state *)res;
 
 	if (state->exit)
 		state->exit(state->clk);
-- 
2.25.1