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Subject[PATCH] drm: sun4i: Fix NULL/invalid pointer dereference in sun8i_tcon_top_un/bind
Date
From: Ondrej Jirman <megous@megous.com>

There are two problems here:

1. Not all clk_data->hws[] need to be initialized, depending on various
configured quirks. This leads to NULL ptr deref in
clk_hw_unregister_gate() in sun8i_tcon_top_unbind()
2. If there is error when registering the clk_data->hws[],
err_unregister_gates error path will try to unregister
IS_ERR()=true (invalid) pointer.

For problem (1) I have this stack trace:

Unable to handle kernel NULL pointer dereference at virtual
address 0000000000000008
Call trace:
clk_hw_unregister+0x8/0x18
clk_hw_unregister_gate+0x14/0x28
sun8i_tcon_top_unbind+0x2c/0x60
component_unbind.isra.4+0x2c/0x50
component_bind_all+0x1d4/0x230
sun4i_drv_bind+0xc4/0x1a0
try_to_bring_up_master+0x164/0x1c0
__component_add+0xa0/0x168
component_add+0x10/0x18
sun8i_dw_hdmi_probe+0x18/0x20
platform_drv_probe+0x3c/0x70
really_probe+0xcc/0x278
driver_probe_device+0x34/0xa8

Problem (2) was identified by head scratching.

Signed-off-by: Ondrej Jirman <megous@megous.com>
---
drivers/gpu/drm/sun4i/sun8i_tcon_top.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun8i_tcon_top.c b/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
index fc36e0c10a37..b1e7c76e9c17 100644
--- a/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
+++ b/drivers/gpu/drm/sun4i/sun8i_tcon_top.c
@@ -227,7 +227,7 @@ static int sun8i_tcon_top_bind(struct device *dev, struct device *master,

err_unregister_gates:
for (i = 0; i < CLK_NUM; i++)
- if (clk_data->hws[i])
+ if (!IS_ERR_OR_NULL(clk_data->hws[i]))
clk_hw_unregister_gate(clk_data->hws[i]);
clk_disable_unprepare(tcon_top->bus);
err_assert_reset:
@@ -245,7 +245,8 @@ static void sun8i_tcon_top_unbind(struct device *dev, struct device *master,

of_clk_del_provider(dev->of_node);
for (i = 0; i < CLK_NUM; i++)
- clk_hw_unregister_gate(clk_data->hws[i]);
+ if (clk_data->hws[i])
+ clk_hw_unregister_gate(clk_data->hws[i]);

clk_disable_unprepare(tcon_top->bus);
reset_control_assert(tcon_top->rst);
--
2.21.0
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