linux-kernel - [PATCH v2] ep93xx: clock: Fix UAF in ep93xx_clk_register

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Date:   Sun, 30 Jan 2022 16:25:02 +0100
From:   Alexander Sverdlin <alexander.sverdlin@...il.com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     Alexander Sverdlin <alexander.sverdlin@...il.com>,
        Hartley Sweeten <hsweeten@...ionengravers.com>,
        Russell King <linux@...linux.org.uk>,
        Nikita Shubin <nikita.shubin@...uefel.me>,
        Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        kernel test robot <lkp@...el.com>, stable@...r.kernel.org
Subject: [PATCH v2] ep93xx: clock: Fix UAF in ep93xx_clk_register_gate()

arch/arm/mach-ep93xx/clock.c:154:2: warning: Use of memory after it is freed [clang-analyzer-unix.Malloc]
arch/arm/mach-ep93xx/clock.c:151:2: note: Taking true branch
if (IS_ERR(clk))
^
arch/arm/mach-ep93xx/clock.c:152:3: note: Memory is released
kfree(psc);
^~~~~~~~~~
arch/arm/mach-ep93xx/clock.c:154:2: note: Use of memory after it is freed
return &psc->hw;
^ ~~~~~~~~

Link: https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org/thread/B5YCO2NJEXINCYE26Y255LCVMO55BGWW/
Reported-by: kernel test robot <lkp@...el.com>
Fixes: 9645ccc7bd7a ("ep93xx: clock: convert in-place to COMMON_CLK")
Cc: stable@...r.kernel.org
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@...il.com>
---
Changelog:
v2:
- Thanks to Nick for the hint to use ERR_CAST()

 arch/arm/mach-ep93xx/clock.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mach-ep93xx/clock.c b/arch/arm/mach-ep93xx/clock.c
index cc75087134d3..4aee14f18123 100644
--- a/arch/arm/mach-ep93xx/clock.c
+++ b/arch/arm/mach-ep93xx/clock.c
@@ -148,8 +148,10 @@ static struct clk_hw *ep93xx_clk_register_gate(const char *name,
 	psc->lock = &clk_lock;
 
 	clk = clk_register(NULL, &psc->hw);
-	if (IS_ERR(clk))
+	if (IS_ERR(clk)) {
 		kfree(psc);
+		return ERR_CAST(clk);
+	}
 
 	return &psc->hw;
 }
-- 
2.34.1