linux-kernel - [PATCH 2/2] firmware: arm_ffa: Explicitly cast return value from NOTIFICATION_INFO

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Message-Id: <20250221095633.506678-2-sudeep.holla@arm.com>
Date: Fri, 21 Feb 2025 09:56:32 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: linux-arm-kernel@...ts.infradead.org
Cc: Sudeep Holla <sudeep.holla@....com>,
	linux-kernel@...r.kernel.org,
	Andrei Homescu <ahomescu@...gle.com>
Subject: [PATCH 2/2] firmware: arm_ffa: Explicitly cast return value from NOTIFICATION_INFO_GET

The return value ret.a2 is of type unsigned long and FFA_RET_NO_DATA is
a negative value.

Since the return value from the firmware can be just 32-bit even on
64-bit systems as FFA specification mentions it as int32 error code in
w0 register, explicitly casting to s32 ensures correct sign interpretation
when comparing against a signed error code FFA_RET_NO_DATA.

Without casting, comparison between unsigned long and a negative
constant could lead to unintended results due to type promotions.

Fixes: 3522be48d82b ("firmware: arm_ffa: Implement the NOTIFICATION_INFO_GET interface")
Reported-by: Andrei Homescu <ahomescu@...gle.com>
Signed-off-by: Sudeep Holla <sudeep.holla@....com>
---
 drivers/firmware/arm_ffa/driver.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
index a77bb205ff7d..31832af7a7bb 100644
--- a/drivers/firmware/arm_ffa/driver.c
+++ b/drivers/firmware/arm_ffa/driver.c
@@ -976,7 +976,7 @@ static void ffa_notification_info_get(void)
 			  }, &ret);
 
 		if (ret.a0 != FFA_FN_NATIVE(SUCCESS) && ret.a0 != FFA_SUCCESS) {
-			if (ret.a2 != FFA_RET_NO_DATA)
+			if ((s32)ret.a2 != FFA_RET_NO_DATA)
 				pr_err("Notification Info fetch failed: 0x%lx (0x%lx)",
 				       ret.a0, ret.a2);
 			return;
-- 
2.34.1