[PATCH v2 3/4] soc: apple: rtkit: reject syslog indices outside the entry count

[Laxman Acharya Padhya <acharyalaxman8848@gmail.com>]

syslog_n_entries is a count, so valid indices range from zero through
syslog_n_entries - 1. The current check also accepts syslog_n_entries
itself.

Reject that index before deriving the shared-buffer offset. The shared
copy bounds check remains the final protection against inconsistent
firmware-provided layouts.

Fixes: 9bd1d9a0d8bb ("soc: apple: Add RTKit IPC library")
Cc: stable@vger.kernel.org
Signed-off-by: Laxman Acharya Padhya <acharyalaxman8848@gmail.com>
---
 drivers/soc/apple/rtkit.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/soc/apple/rtkit.c b/drivers/soc/apple/rtkit.c
index 2e62f9b3c948..da766df5a6d7 100644
--- a/drivers/soc/apple/rtkit.c
+++ b/drivers/soc/apple/rtkit.c
@@ -481,7 +481,7 @@ static void apple_rtkit_syslog_rx_log(struct apple_rtkit *rtk, u64 msg)
 			"RTKit: received syslog message but no syslog_buffer.buffer or syslog_buffer.iomem\n");
 		goto done;
 	}
-	if (idx > rtk->syslog_n_entries) {
+	if (idx >= rtk->syslog_n_entries) {
 		dev_warn(rtk->dev, "RTKit: syslog index %d out of range\n",
 			 idx);
 		goto done;
-- 
2.51.2