efi: Fix handling error value in fdt_find_uefi_params

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@samsung.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Shawn Lin <shawn.lin@rock-chips.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index 5a2631af7410782dc8f7ba993ab0b1139bf71abb..7dd2e2d372317f8a4ddb1fe464b29f662a001a28 100644 (file)
--- 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);