linux-kernel - [PATCH 2/6] efi: Fix handling error value in fdt_find_uefi

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Date:   Mon,  5 Sep 2016 15:42:33 +0100
From:   Matt Fleming <matt@...eblueprint.co.uk>
To:     Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Mark Rutland <mark.rutland@....com>,
        Shawn Lin <shawn.lin@...k-chips.com>, stable@...r.kernel.org
Subject: [PATCH 2/6] efi: Fix handling error value in fdt_find_uefi_params

From: Andrzej Hajda <a.hajda@...sung.com>

of_get_flat_dt_subnode_by_name can return negative value in case of error.
Assigning the result to unsigned variable and checking if the variable
is lesser than zero is incorrect and always false.
The patch fixes it by using signed variable to check the result.

The problem has been detected using semantic patch
scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci

Signed-off-by: Andrzej Hajda <a.hajda@...sung.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: Shawn Lin <shawn.lin@...k-chips.com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Matt Fleming <matt@...eblueprint.co.uk>
---
 drivers/firmware/efi/efi.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 5a2631af7410..7dd2e2d37231 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -657,9 +657,12 @@ static int __init fdt_find_uefi_params(unsigned long node, const char *uname,
 		}
 
 		if (subnode) {
-			node = of_get_flat_dt_subnode_by_name(node, subnode);
-			if (node < 0)
+			int err = of_get_flat_dt_subnode_by_name(node, subnode);
+
+			if (err < 0)
 				return 0;
+
+			node = err;
 		}
 
 		return __find_uefi_params(node, info, dt_params[i].params);
-- 
2.9.3