linux-kernel - [PATCH 1/2] clk: Fix clk_core

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Date: Sat, 02 Mar 2024 00:52:14 +0000
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: Michael Turquette <mturquette@...libre.com>, 
 Stephen Boyd <sboyd@...nel.org>, Bjorn Andersson <andersson@...nel.org>, 
 Konrad Dybcio <konrad.dybcio@...aro.org>, 
 Rajendra Nayak <quic_rjendra@...cinc.com>, Abel Vesa <abel.vesa@...aro.org>
Cc: linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-arm-msm@...r.kernel.org, 
 Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Subject: [PATCH 1/2] clk: Fix clk_core_get NULL dereference

It is possible for clk_core_get to dereference a NULL in the following
sequence:

clk_core_get()
    of_clk_get_hw_from_clkspec()
        __of_clk_get_hw_from_provider()
            __clk_get_hw()

__clk_get_hw() can return NULL which is dereferenced by clk_core_get() at
hw->core.

Prior to commit dde4eff47c82 ("clk: Look for parents with clkdev based
clk_lookups") the check IS_ERR_OR_NULL() was performed which would have
caught the NULL.

Reading the description of this function it talks about returning NULL but
that cannot be so at the moment.

Update the function to check for hw before dereferencing it and return NULL
if hw is NULL.

Fixes: dde4eff47c82 ("clk: Look for parents with clkdev based clk_lookups")
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
---
 drivers/clk/clk.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index a3bc7fb90d0f..25371c91a58f 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -418,6 +418,9 @@ static struct clk_core *clk_core_get(struct clk_core *core, u8 p_index)
 	if (IS_ERR(hw))
 		return ERR_CAST(hw);

+	if (!hw)
+		return NULL;
+
 	return hw->core;
 }

-- 
2.43.0