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
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
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]>
---
arch/s390/appldata/appldata_os.c | 2 +-
drivers/s390/block/dasd_diag.c | 2 +-
drivers/s390/block/dasd_eckd.h | 2 +-
drivers/s390/char/raw3270.h | 2 +-
drivers/s390/char/sclp_pci.c | 2 +-
drivers/s390/cio/idset.c | 2 +-
drivers/s390/crypto/pkey_api.c | 2 +-
drivers/s390/crypto/zcrypt_ccamisc.h | 2 +-
drivers/s390/crypto/zcrypt_msgtype6.c | 2 +-
9 files changed, 9 insertions(+), 9 deletions(-)
diff --git a/arch/s390/appldata/appldata_os.c b/arch/s390/appldata/appldata_os.c
index 54f375627532..8bf46d705957 100644
--- a/arch/s390/appldata/appldata_os.c
+++ b/arch/s390/appldata/appldata_os.c
@@ -75,7 +75,7 @@ struct appldata_os_data {
(waiting for I/O) */
/* per cpu data */
- struct appldata_os_per_cpu os_cpu[0];
+ struct appldata_os_per_cpu os_cpu[];
} __attribute__((packed));
static struct appldata_os_data *appldata_os_data;
diff --git a/drivers/s390/block/dasd_diag.c b/drivers/s390/block/dasd_diag.c
index 8d4971645cf1..facb588d09e4 100644
--- a/drivers/s390/block/dasd_diag.c
+++ b/drivers/s390/block/dasd_diag.c
@@ -58,7 +58,7 @@ struct dasd_diag_private {
struct dasd_diag_req {
unsigned int block_count;
- struct dasd_diag_bio bio[0];
+ struct dasd_diag_bio bio[];
};
static const u8 DASD_DIAG_CMS1[] = { 0xc3, 0xd4, 0xe2, 0xf1 };/* EBCDIC CMS1 */
diff --git a/drivers/s390/block/dasd_eckd.h b/drivers/s390/block/dasd_eckd.h
index 6943508d0f1d..ca24a78a256e 100644
--- a/drivers/s390/block/dasd_eckd.h
+++ b/drivers/s390/block/dasd_eckd.h
@@ -220,7 +220,7 @@ struct LRE_eckd_data {
__u8 imbedded_count;
__u8 extended_operation;
__u16 extended_parameter_length;
- __u8 extended_parameter[0];
+ __u8 extended_parameter[];
} __attribute__ ((packed));
/* Prefix data for format 0x00 and 0x01 */
diff --git a/drivers/s390/char/raw3270.h b/drivers/s390/char/raw3270.h
index 3afaa35f7351..08f36e973b43 100644
--- a/drivers/s390/char/raw3270.h
+++ b/drivers/s390/char/raw3270.h
@@ -211,7 +211,7 @@ struct string
struct list_head update;
unsigned long size;
unsigned long len;
- char string[0];
+ char string[];
} __attribute__ ((aligned(8)));
static inline struct string *
diff --git a/drivers/s390/char/sclp_pci.c b/drivers/s390/char/sclp_pci.c
index 995e9196852e..a3e5a5fb0c1e 100644
--- a/drivers/s390/char/sclp_pci.c
+++ b/drivers/s390/char/sclp_pci.c
@@ -39,7 +39,7 @@ struct err_notify_evbuf {
u8 atype;
u32 fh;
u32 fid;
- u8 data[0];
+ u8 data[];
} __packed;
struct err_notify_sccb {
diff --git a/drivers/s390/cio/idset.c b/drivers/s390/cio/idset.c
index 835de44dbbcc..77d0ea7b381b 100644
--- a/drivers/s390/cio/idset.c
+++ b/drivers/s390/cio/idset.c
@@ -13,7 +13,7 @@
struct idset {
int num_ssid;
int num_id;
- unsigned long bitmap[0];
+ unsigned long bitmap[];
};
static inline unsigned long bitmap_size(int num_ssid, int num_id)
diff --git a/drivers/s390/crypto/pkey_api.c b/drivers/s390/crypto/pkey_api.c
index 2f33c5fcf676..74e63ec49068 100644
--- a/drivers/s390/crypto/pkey_api.c
+++ b/drivers/s390/crypto/pkey_api.c
@@ -80,7 +80,7 @@ struct clearaeskeytoken {
u8 res1[3];
u32 keytype; /* key type, one of the PKEY_KEYTYPE values */
u32 len; /* bytes actually stored in clearkey[] */
- u8 clearkey[0]; /* clear key value */
+ u8 clearkey[]; /* clear key value */
} __packed;
/*
diff --git a/drivers/s390/crypto/zcrypt_ccamisc.h b/drivers/s390/crypto/zcrypt_ccamisc.h
index 3a9876d5ab0e..8b7a641671c9 100644
--- a/drivers/s390/crypto/zcrypt_ccamisc.h
+++ b/drivers/s390/crypto/zcrypt_ccamisc.h
@@ -90,7 +90,7 @@ struct cipherkeytoken {
u16 kmf1; /* key management field 1 */
u16 kmf2; /* key management field 2 */
u16 kmf3; /* key management field 3 */
- u8 vdata[0]; /* variable part data follows */
+ u8 vdata[]; /* variable part data follows */
} __packed;
/* Some defines for the CCA AES cipherkeytoken kmf1 field */
diff --git a/drivers/s390/crypto/zcrypt_msgtype6.c b/drivers/s390/crypto/zcrypt_msgtype6.c
index a36251d138fb..eadd3a438a4b 100644
--- a/drivers/s390/crypto/zcrypt_msgtype6.c
+++ b/drivers/s390/crypto/zcrypt_msgtype6.c
@@ -590,7 +590,7 @@ struct type86x_reply {
struct CPRBX cprbx;
unsigned char pad[4]; /* 4 byte function code/rules block ? */
unsigned short length;
- char text[0];
+ char text[];
} __packed;
struct type86_ep11_reply {
--
2.25.0
On Fri, Feb 21, 2020 at 09:06:12AM -0600, Gustavo A. R. Silva wrote:
> 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
> inadvertently introduced[3] to the codebase from now on.
>
> Also, notice that, dynamic memory allocations won't be affected by
> this change:
>
> "Flexible array members have incomplete type, and so the sizeof operator
> may not be applied. As a quirk of the original implementation of
> zero-length arrays, sizeof evaluates to zero."[1]
>
> 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]>
> ---
> arch/s390/appldata/appldata_os.c | 2 +-
> drivers/s390/block/dasd_diag.c | 2 +-
> drivers/s390/block/dasd_eckd.h | 2 +-
> drivers/s390/char/raw3270.h | 2 +-
> drivers/s390/char/sclp_pci.c | 2 +-
> drivers/s390/cio/idset.c | 2 +-
> drivers/s390/crypto/pkey_api.c | 2 +-
> drivers/s390/crypto/zcrypt_ccamisc.h | 2 +-
> drivers/s390/crypto/zcrypt_msgtype6.c | 2 +-
> 9 files changed, 9 insertions(+), 9 deletions(-)
>
Applied, thanks
On 2/25/20 07:57, Vasily Gorbik wrote:
>>
>> [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]>
>> ---
>> arch/s390/appldata/appldata_os.c | 2 +-
>> drivers/s390/block/dasd_diag.c | 2 +-
>> drivers/s390/block/dasd_eckd.h | 2 +-
>> drivers/s390/char/raw3270.h | 2 +-
>> drivers/s390/char/sclp_pci.c | 2 +-
>> drivers/s390/cio/idset.c | 2 +-
>> drivers/s390/crypto/pkey_api.c | 2 +-
>> drivers/s390/crypto/zcrypt_ccamisc.h | 2 +-
>> drivers/s390/crypto/zcrypt_msgtype6.c | 2 +-
>> 9 files changed, 9 insertions(+), 9 deletions(-)
>>
>
> Applied, thanks
>
Thanks, Vasily.
--
Gustavo