diff mbox series

drivers/mux: Fix comparison of signed and unsigned integers in adgs1408.c

Message ID MEAPR01MB42314FB7FB4627E0B58E6AC6C9659@MEAPR01MB4231.ausprd01.prod.outlook.com
State New
Headers show
Series drivers/mux: Fix comparison of signed and unsigned integers in adgs1408.c | expand

Commit Message

Ping Li April 26, 2023, 4:50 a.m. UTC 
Hello,

I found a bug in the drivers/mux/adgs1408.c driver that causes MUX_IDLE_AS_IS mode does not work at all.
Specifically, the comparison "if (idle_state < mux->states)" in the switch statement fails due to Usual arithmetic conversions if idle_state is set to a negative value, such as MUX_IDLE_AS_IS (-1). Refer to The C standard (ISO/IEC 9899:2011), section 6.3.1.8  Usual arithmetic conversions https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf#page=52.

To fix this issue, I suggest adding an explicit type cast to the comparison.
Here's the modified code:
diff mbox series

Patch

From e96bb5ab8b5c7e1dcda4ffeffc64d6b120579baf Mon Sep 17 00:00:00 2001
From: "Ping.Li" <Ping.Li@rfi.com.au>
Date: Wed, 26 Apr 2023 13:52:53 +0930
Subject: [PATCH] Fix comparison of signed and unsigned integers in adgs1408.c

Signed-off-by: Ping.Li <Ping.Li@rfi.com.au>
---
 drivers/mux/adgs1408.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/mux/adgs1408.c b/drivers/mux/adgs1408.c
index 22ed051eb1a4..c59e0bed80d1 100644
--- a/drivers/mux/adgs1408.c
+++ b/drivers/mux/adgs1408.c
@@ -89,7 +89,9 @@  static int adgs1408_probe(struct spi_device *spi)
 	case MUX_IDLE_AS_IS:
 	case 0 ... 7:
 		/* adgs1409 supports only 4 states */
-		if (idle_state < mux->states) {
+		/* the idle_state will be implicitly converted to an unsigned int in
+		   the comparison, which will fail the comparison if without (int) */
+		if (idle_state < (int)mux->states) {
 			mux->idle_state = idle_state;
 			break;
 		}
-- 
2.25.1