linux-kernel - [PATCH] platform/x86: ibm_rtl: fix EBDA signature search pointer arithmetic

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Message-ID:
 <SYBPR01MB78812D887A92DE3802D0D06EAFA9A@SYBPR01MB7881.ausprd01.prod.outlook.com>
Date: Fri, 19 Dec 2025 16:30:29 +0800
From: Junrui Luo <moonafterrain@...look.com>
To: Hans de Goede <hansg@...nel.org>, 
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, 
 Vernon Mauery <vernux@...ibm.com>, Matthew Garrett <mjg@...hat.com>
Cc: platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Yuhao Jiang <danisjiang@...il.com>, Junrui Luo <moonafterrain@...look.com>
Subject: [PATCH] platform/x86: ibm_rtl: fix EBDA signature search pointer
 arithmetic

The ibm_rtl_init() function searches for the signature but has a pointer
arithmetic error. The loop counter suggests searching at 4-byte intervals
but the implementation only advances by 1 byte per iteration.

Fix by properly advancing the pointer by sizeof(unsigned int) bytes
each iteration.

Reported-by: Yuhao Jiang <danisjiang@...il.com>
Reported-by: Junrui Luo <moonafterrain@...look.com>
Fixes: 35f0ce032b0f ("IBM Real-Time "SMI Free" mode driver -v7")
Signed-off-by: Junrui Luo <moonafterrain@...look.com>
---
 drivers/platform/x86/ibm_rtl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/platform/x86/ibm_rtl.c b/drivers/platform/x86/ibm_rtl.c
index 231b37909801..139956168cf9 100644
--- a/drivers/platform/x86/ibm_rtl.c
+++ b/drivers/platform/x86/ibm_rtl.c
@@ -273,7 +273,7 @@ static int __init ibm_rtl_init(void) {
 	/* search for the _RTL_ signature at the start of the table */
 	for (i = 0 ; i < ebda_size/sizeof(unsigned int); i++) {
 		struct ibm_rtl_table __iomem * tmp;
-		tmp = (struct ibm_rtl_table __iomem *) (ebda_map+i);
+		tmp = (struct ibm_rtl_table __iomem *) (ebda_map + i*sizeof(unsigned int));
 		if ((readq(&tmp->signature) & RTL_MASK) == RTL_SIGNATURE) {
 			phys_addr_t addr;
 			unsigned int plen;

---
base-commit: ea1013c1539270e372fc99854bc6e4d94eaeff66
change-id: 20251219-fixes-4daa45346b5c

Best regards,
-- 
Junrui Luo <moonafterrain@...look.com>