s390: 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
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")

Link: https://lkml.kernel.org/r/20200221150612.GA9717@embeddedor
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

diff --git a/arch/s390/appldata/appldata_os.c b/arch/s390/appldata/appldata_os.c
index 54f3756..8bf46d7 100644 (file)
--- 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 8d49716..facb588 100644 (file)
--- 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 6943508..ca24a78 100644 (file)
--- 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 3afaa35..08f36e9 100644 (file)
--- 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 995e919..a3e5a5f 100644 (file)
--- 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 835de44..77d0ea7 100644 (file)
--- 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 2f33c5f..74e63ec 100644 (file)
--- 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 3a9876d..8b7a641 100644 (file)
--- 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 a36251d..eadd3a4 100644 (file)
--- 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 {