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From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Sudeep Holla <sudeep.holla@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: [PATCH] firmware: arm_scmi: driver: Replace zero-length array with flexible-array member
Date: Tue, 11 Feb 2020 17:10:45 -0600	[thread overview]
Message-ID: <20200211231045.GA13956@embeddedor> (raw)

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertenly introduced[3] to the codebase from now on.

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/firmware/arm_scmi/driver.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 8f952f2f1a29..b40f71edc92d 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -148,7 +148,7 @@ struct scmi_shared_mem {
 #define SCMI_SHMEM_FLAG_INTR_ENABLED	BIT(0)
 	__le32 length;
 	__le32 msg_header;
-	u8 msg_payload[0];
+	u8 msg_payload[];
 };
 
 static const int scmi_linux_errmap[] = {
-- 
2.25.0


WARNING: multiple messages have this Message-ID (diff)
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Sudeep Holla <sudeep.holla@arm.com>
Cc: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: [PATCH] firmware: arm_scmi: driver: Replace zero-length array with flexible-array member
Date: Tue, 11 Feb 2020 17:10:45 -0600	[thread overview]
Message-ID: <20200211231045.GA13956@embeddedor> (raw)

The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertenly introduced[3] to the codebase from now on.

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/firmware/arm_scmi/driver.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 8f952f2f1a29..b40f71edc92d 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -148,7 +148,7 @@ struct scmi_shared_mem {
 #define SCMI_SHMEM_FLAG_INTR_ENABLED	BIT(0)
 	__le32 length;
 	__le32 msg_header;
-	u8 msg_payload[0];
+	u8 msg_payload[];
 };
 
 static const int scmi_linux_errmap[] = {
-- 
2.25.0


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             reply	other threads:[~2020-02-11 23:08 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-11 23:10 Gustavo A. R. Silva [this message]
2020-02-11 23:10 ` [PATCH] firmware: arm_scmi: driver: Replace zero-length array with flexible-array member Gustavo A. R. Silva
2020-02-20 17:18 ` Sudeep Holla
2020-02-20 17:18   ` Sudeep Holla
2020-02-21 15:08   ` Gustavo A. R. Silva
2020-02-21 15:08     ` Gustavo A. R. Silva

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