linux-kernel - [PATCH] usb: ftdi-elan: Fix undefined behaviour

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Message-Id: <20220401075747.2407536-1-lv.ruyi@zte.com.cn>
Date:   Fri,  1 Apr 2022 07:57:47 +0000
From:   cgel.zte@...il.com
To:     gregkh@...uxfoundation.org
Cc:     weiyongjun1@...wei.com, colin.king@...el.com, lv.ruyi@....com.cn,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Zeal Robot <zealci@....com.cn>
Subject: [PATCH] usb: ftdi-elan: Fix undefined behaviour

From: Lv Ruyi <lv.ruyi@....com.cn>

The use of zero-sized array causes undefined behaviour when it is not
the last member in a structure. As it happens to be in this case.

Also, the current code makes use of a language extension to the C90
standard, but the preferred mechanism to declare variable-length
types such as this one is a flexible array member, 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. Which is beneficial
to cultivate a high-quality code.

Reported-by: Zeal Robot <zealci@....com.cn>
Signed-off-by: Lv Ruyi <lv.ruyi@....com.cn>
---
 drivers/usb/misc/ftdi-elan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/misc/ftdi-elan.c b/drivers/usb/misc/ftdi-elan.c
index 6c38c62d29b2..e818d2ed6831 100644
--- a/drivers/usb/misc/ftdi-elan.c
+++ b/drivers/usb/misc/ftdi-elan.c
@@ -171,7 +171,6 @@ struct usb_ftdi {
 	struct delayed_work command_work;
 	struct delayed_work respond_work;
 	struct u132_platform_data platform_data;
-	struct resource resources[0];
 	struct platform_device platform_dev;
 	unsigned char *bulk_in_buffer;
 	size_t bulk_in_size;
@@ -185,6 +184,7 @@ struct usb_ftdi {
 	int expected;
 	int received;
 	int ed_found;
+	struct resource resources[];
 };
 #define kref_to_usb_ftdi(d) container_of(d, struct usb_ftdi, kref)
 #define platform_device_to_usb_ftdi(d) container_of(d, struct usb_ftdi, \
-- 
2.25.1