linux-kernel - [PATCH] clk: mediatek: mt6797: Fix a NULL pointer dereference in mtk_infrasys_init

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Message-Id: <20211130092731.83763-1-zhou1615@umn.edu>
Date:   Tue, 30 Nov 2021 17:27:30 +0800
From:   Zhou Qingyang <zhou1615@....edu>
To:     zhou1615@....edu
Cc:     kjlu@....edu, Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Kevin-CW Chen <kevin-cw.chen@...iatek.com>,
        Mars Cheng <mars.cheng@...iatek.com>,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] clk: mediatek: mt6797: Fix a NULL pointer dereference in mtk_infrasys_init_early()

In mtk_infrasys_init_early(), mtk_alloc_clk_data() is assigned to
clk_data, and there is a dereference of it in
mtk_infrasys_init_early(), which could lead to a NULL pointer
dereference on failure of mtk_alloc_clk_data().

Fix this bug by adding a check of infra_clk_data.

This bug was found by a static analyzer. The analysis employs
differential checking to identify inconsistent security operations
(e.g., checks or kfrees) between two code paths and confirms that the
inconsistent operations are not recovered in the current function or
the callers, so they constitute bugs.

Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.

Builds with CONFIG_COMMON_CLK_MT6796=y show no new warnings, and our
static analyzer no longer warns about this code.

Fixes: 96596aa06628 ("clk: mediatek: add clk support for MT6797")
Signed-off-by: Zhou Qingyang <zhou1615@....edu>
---
 drivers/clk/mediatek/clk-mt6797.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/clk/mediatek/clk-mt6797.c b/drivers/clk/mediatek/clk-mt6797.c
index 428eb24ffec5..184b283b6926 100644
--- a/drivers/clk/mediatek/clk-mt6797.c
+++ b/drivers/clk/mediatek/clk-mt6797.c
@@ -563,6 +563,11 @@ static void mtk_infrasys_init_early(struct device_node *node)

 	if (!infra_clk_data) {
 		infra_clk_data = mtk_alloc_clk_data(CLK_INFRA_NR);
+		if (!infra_clk_data) {
+			pr_err("%s(): could not register clock provider: %d\n",
+				__func__, -ENOMEM);
+			return;
+		}

 		for (i = 0; i < CLK_INFRA_NR; i++)
 			infra_clk_data->clks[i] = ERR_PTR(-EPROBE_DEFER);
-- 
2.25.1