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

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

[Junrui Luo]

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@gmail.com>
Reported-by: Junrui Luo <moonafterrain@outlook.com>
Fixes: 35f0ce032b0f ("IBM Real-Time "SMI Free" mode driver -v7")
Signed-off-by: Junrui Luo <moonafterrain@outlook.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@outlook.com>

Re: [PATCH] platform/x86: ibm_rtl: fix EBDA signature search pointer arithmetic

[Ilpo Järvinen]

On Fri, 19 Dec 2025 16:30:29 +0800, Junrui Luo wrote:

> 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.
> 
> [...]


Thank you for your contribution, it has been applied to my local
review-ilpo-fixes branch. Note it will show up in the public
platform-drivers-x86/review-ilpo-fixes branch only once I've pushed my
local branch there, which might take a while.

The list of commits applied:
[1/1] platform/x86: ibm_rtl: fix EBDA signature search pointer arithmetic
      commit: 15dd100349b8526cbdf2de0ce3e72e700eb6c208

--
 i.