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 <[email protected]>
---
drivers/misc/mei/bus-fixup.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/misc/mei/bus-fixup.c b/drivers/misc/mei/bus-fixup.c
index 5fcac02233af..aa3648d59a8a 100644
--- a/drivers/misc/mei/bus-fixup.c
+++ b/drivers/misc/mei/bus-fixup.c
@@ -107,7 +107,7 @@ struct mkhi_rule_id {
struct mkhi_fwcaps {
struct mkhi_rule_id id;
u8 len;
- u8 data[0];
+ u8 data[];
} __packed;
struct mkhi_fw_ver_block {
@@ -135,7 +135,7 @@ struct mkhi_msg_hdr {
struct mkhi_msg {
struct mkhi_msg_hdr hdr;
- u8 data[0];
+ u8 data[];
} __packed;
#define MKHI_OSVER_BUF_LEN (sizeof(struct mkhi_msg_hdr) + \
--
2.25.0
> -----Original Message-----
> From: Gustavo A. R. Silva <[email protected]>
> Sent: Tuesday, February 11, 2020 23:08
> To: Winkler, Tomas <[email protected]>; Arnd Bergmann
> <[email protected]>; Greg Kroah-Hartman <[email protected]>
> Cc: [email protected]; Gustavo A. R. Silva
> <[email protected]>
> Subject: [PATCH] mei: bus: replace zero-length array with flexible-array member
>
> 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 <[email protected]>
Ack.
> ---
> drivers/misc/mei/bus-fixup.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/misc/mei/bus-fixup.c b/drivers/misc/mei/bus-fixup.c index
> 5fcac02233af..aa3648d59a8a 100644
> --- a/drivers/misc/mei/bus-fixup.c
> +++ b/drivers/misc/mei/bus-fixup.c
> @@ -107,7 +107,7 @@ struct mkhi_rule_id { struct mkhi_fwcaps {
> struct mkhi_rule_id id;
> u8 len;
> - u8 data[0];
> + u8 data[];
> } __packed;
>
> struct mkhi_fw_ver_block {
> @@ -135,7 +135,7 @@ struct mkhi_msg_hdr {
>
> struct mkhi_msg {
> struct mkhi_msg_hdr hdr;
> - u8 data[0];
> + u8 data[];
> } __packed;
>
> #define MKHI_OSVER_BUF_LEN (sizeof(struct mkhi_msg_hdr) + \
> --
> 2.25.0