linux-kernel - [PATCH v2 09/16] clk: spear: Remove uninitialized

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Date:   Fri, 19 Jun 2020 20:30:00 -0700
From:   Kees Cook <keescook@...omium.org>
To:     linux-kernel@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Joe Perches <joe@...ches.com>,
        Andy Whitcroft <apw@...onical.com>, x86@...nel.org,
        drbd-dev@...ts.linbit.com, linux-block@...r.kernel.org,
        b43-dev@...ts.infradead.org, netdev@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-wireless@...r.kernel.org,
        linux-ide@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-spi@...r.kernel.org, linux-mm@...ck.org,
        clang-built-linux@...glegroups.com
Subject: [PATCH v2 09/16] clk: spear: Remove uninitialized_var() usage

Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings (e.g.
"unused variable"). If the compiler thinks it is uninitialized, either
simply initialize the variable or make compiler changes. As a precursor
to removing[2] this[3] macro[4], initialize "i" to zero. The compiler
warning was not a false positive, since clk_pll_set_rate()'s call to
clk_pll_round_rate_index() will always fail (since "prate" is NULL), so
"i" was never being initialized.

[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Fixes: 7d4998f71b29 ("clk: SPEAr: Vco-pll: Fix compilation warning")
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/clk/spear/clk-vco-pll.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/spear/clk-vco-pll.c b/drivers/clk/spear/clk-vco-pll.c
index c08dec30bfa6..fed194169666 100644
--- a/drivers/clk/spear/clk-vco-pll.c
+++ b/drivers/clk/spear/clk-vco-pll.c
@@ -147,7 +147,7 @@ static int clk_pll_set_rate(struct clk_hw *hw, unsigned long drate,
 	struct clk_pll *pll = to_clk_pll(hw);
 	struct pll_rate_tbl *rtbl = pll->vco->rtbl;
 	unsigned long flags = 0, val;
-	int uninitialized_var(i);
+	int i = 0;
 
 	clk_pll_round_rate_index(hw, drate, NULL, &i);
 
-- 
2.25.1