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RDMA: Replace zero-length array with flexible-array member

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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 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

Link: https://lore.kernel.org/r/20200213010425.GA13068@embeddedor.com
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com> # added a few more
This commit is contained in:
Gustavo A. R. Silva
2020-02-12 19:04:25 -06:00
committed by Jason Gunthorpe
parent 52c5e9e749
commit 5b361328ca
25 changed files with 44 additions and 44 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
include/rdma/ib_verbs.h
View File

@@ -1876,7 +1876,7 @@ struct ib_flow_eth_filter {
__be16 ether_type;
__be16 vlan_tag;
/* Must be last */
u8 real_sz[0];
u8 real_sz[];
};
struct ib_flow_spec_eth {
@@ -1890,7 +1890,7 @@ struct ib_flow_ib_filter {
__be16 dlid;
__u8 sl;
/* Must be last */
u8 real_sz[0];
u8 real_sz[];
};
struct ib_flow_spec_ib {
@@ -1915,7 +1915,7 @@ struct ib_flow_ipv4_filter {
u8 ttl;
u8 flags;
/* Must be last */
u8 real_sz[0];
u8 real_sz[];
};
struct ib_flow_spec_ipv4 {
@@ -1933,7 +1933,7 @@ struct ib_flow_ipv6_filter {
u8 traffic_class;
u8 hop_limit;
/* Must be last */
u8 real_sz[0];
u8 real_sz[];
};
struct ib_flow_spec_ipv6 {
@@ -1947,7 +1947,7 @@ struct ib_flow_tcp_udp_filter {
__be16 dst_port;
__be16 src_port;
/* Must be last */
u8 real_sz[0];
u8 real_sz[];
};
struct ib_flow_spec_tcp_udp {
@@ -1959,7 +1959,7 @@ struct ib_flow_spec_tcp_udp {
struct ib_flow_tunnel_filter {
__be32 tunnel_id;
u8 real_sz[0];
u8 real_sz[];
};
/* ib_flow_spec_tunnel describes the Vxlan tunnel
@@ -1976,7 +1976,7 @@ struct ib_flow_esp_filter {
__be32 spi;
__be32 seq;
/* Must be last */
u8 real_sz[0];
u8 real_sz[];
};
struct ib_flow_spec_esp {
@@ -1991,7 +1991,7 @@ struct ib_flow_gre_filter {
__be16 protocol;
__be32 key;
/* Must be last */
u8 real_sz[0];
u8 real_sz[];
};
struct ib_flow_spec_gre {
@@ -2004,7 +2004,7 @@ struct ib_flow_spec_gre {
struct ib_flow_mpls_filter {
__be32 tag;
/* Must be last */
u8 real_sz[0];
u8 real_sz[];
};
struct ib_flow_spec_mpls {