linux-kernel - [PATCH AUTOSEL 5.4 112/459] clk: qcom: rcg2: Don't crash if our parent can't be found; return an error

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Date:   Fri, 14 Feb 2020 10:56:02 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Douglas Anderson <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Sasha Levin <sashal@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-clk@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 112/459] clk: qcom: rcg2: Don't crash if our parent can't be found; return an error

From: Douglas Anderson <dianders@...omium.org>

[ Upstream commit 908b050114d8fefdddc57ec9fbc213c3690e7f5f ]

When I got my clock parenting slightly wrong I ended up with a crash
that looked like this:

  Unable to handle kernel NULL pointer dereference at virtual
  address 0000000000000000
  ...
  pc : clk_hw_get_rate+0x14/0x44
  ...
  Call trace:
   clk_hw_get_rate+0x14/0x44
   _freq_tbl_determine_rate+0x94/0xfc
   clk_rcg2_determine_rate+0x2c/0x38
   clk_core_determine_round_nolock+0x4c/0x88
   clk_core_round_rate_nolock+0x6c/0xa8
   clk_core_round_rate_nolock+0x9c/0xa8
   clk_core_set_rate_nolock+0x70/0x180
   clk_set_rate+0x3c/0x6c
   of_clk_set_defaults+0x254/0x360
   platform_drv_probe+0x28/0xb0
   really_probe+0x120/0x2dc
   driver_probe_device+0x64/0xfc
   device_driver_attach+0x4c/0x6c
   __driver_attach+0xac/0xc0
   bus_for_each_dev+0x84/0xcc
   driver_attach+0x2c/0x38
   bus_add_driver+0xfc/0x1d0
   driver_register+0x64/0xf8
   __platform_driver_register+0x4c/0x58
   msm_drm_register+0x5c/0x60
   ...

It turned out that clk_hw_get_parent_by_index() was returning NULL and
we weren't checking.  Let's check it so that we don't crash.

Fixes: ac269395cdd8 ("clk: qcom: Convert to clk_hw based provider APIs")
Signed-off-by: Douglas Anderson <dianders@...omium.org>
Reviewed-by: Matthias Kaehlcke <mka@...omium.org>
Link: https://lkml.kernel.org/r/20200203103049.v4.1.I7487325fe8e701a68a07d3be8a6a4b571eca9cfa@changeid
Signed-off-by: Stephen Boyd <sboyd@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/clk/qcom/clk-rcg2.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/clk/qcom/clk-rcg2.c b/drivers/clk/qcom/clk-rcg2.c
index 5174222cbfab2..a88101480e337 100644
--- a/drivers/clk/qcom/clk-rcg2.c
+++ b/drivers/clk/qcom/clk-rcg2.c
@@ -217,6 +217,9 @@ static int _freq_tbl_determine_rate(struct clk_hw *hw, const struct freq_tbl *f,

 	clk_flags = clk_hw_get_flags(hw);
 	p = clk_hw_get_parent_by_index(hw, index);
+	if (!p)
+		return -EINVAL;
+
 	if (clk_flags & CLK_SET_RATE_PARENT) {
 		rate = f->freq;
 		if (f->pre_div) {
-- 
2.20.1