* [PATCH][next] netronome: Replace zero-length array with flexible-array member
@ 2020-02-24 16:36 Gustavo A. R. Silva
2020-02-24 23:26 ` David Miller
0 siblings, 1 reply; 3+ messages in thread
From: Gustavo A. R. Silva @ 2020-02-24 16:36 UTC (permalink / raw)
To: Jakub Kicinski, David S. Miller, Alexei Starovoitov,
Daniel Borkmann, Martin KaFai Lau, Song Liu, Yonghong Song,
Andrii Nakryiko
Cc: netdev, bpf, oss-drivers, linux-kernel, Gustavo A. R. Silva
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 <gustavo@embeddedor.com>
---
drivers/net/ethernet/netronome/nfp/bpf/fw.h | 6 +++---
drivers/net/ethernet/netronome/nfp/flower/cmsg.h | 4 ++--
drivers/net/ethernet/netronome/nfp/nfp_main.h | 2 +-
drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c | 8 ++++----
drivers/net/ethernet/netronome/nfp/nfp_net_repr.h | 2 +-
drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp.h | 2 +-
6 files changed, 12 insertions(+), 12 deletions(-)
diff --git a/drivers/net/ethernet/netronome/nfp/bpf/fw.h b/drivers/net/ethernet/netronome/nfp/bpf/fw.h
index a83a0ad5e27d..4268a7e0f344 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/fw.h
+++ b/drivers/net/ethernet/netronome/nfp/bpf/fw.h
@@ -104,14 +104,14 @@ struct cmsg_req_map_op {
__be32 tid;
__be32 count;
__be32 flags;
- u8 data[0];
+ u8 data[];
};
struct cmsg_reply_map_op {
struct cmsg_reply_map_simple reply_hdr;
__be32 count;
__be32 resv;
- u8 data[0];
+ u8 data[];
};
struct cmsg_bpf_event {
@@ -120,6 +120,6 @@ struct cmsg_bpf_event {
__be64 map_ptr;
__be32 data_size;
__be32 pkt_size;
- u8 data[0];
+ u8 data[];
};
#endif
diff --git a/drivers/net/ethernet/netronome/nfp/flower/cmsg.h b/drivers/net/ethernet/netronome/nfp/flower/cmsg.h
index 9b50d76bbc09..bf516285510f 100644
--- a/drivers/net/ethernet/netronome/nfp/flower/cmsg.h
+++ b/drivers/net/ethernet/netronome/nfp/flower/cmsg.h
@@ -587,7 +587,7 @@ struct nfp_flower_cmsg_mac_repr {
u8 info;
u8 nbi_port;
u8 phys_port;
- } ports[0];
+ } ports[];
};
#define NFP_FLOWER_CMSG_MAC_REPR_NBI GENMASK(1, 0)
@@ -619,7 +619,7 @@ struct nfp_flower_cmsg_merge_hint {
struct {
__be32 host_ctx;
__be64 host_cookie;
- } __packed flow[0];
+ } __packed flow[];
};
enum nfp_flower_cmsg_port_type {
diff --git a/drivers/net/ethernet/netronome/nfp/nfp_main.h b/drivers/net/ethernet/netronome/nfp/nfp_main.h
index 5d5812fd9317..fa6b13a05941 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_main.h
+++ b/drivers/net/ethernet/netronome/nfp/nfp_main.h
@@ -42,7 +42,7 @@ struct nfp_shared_buf;
*/
struct nfp_dumpspec {
u32 size;
- u8 data[0];
+ u8 data[];
};
/**
diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c b/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
index 769ceef09756..a614df095b08 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_debugdump.c
@@ -36,7 +36,7 @@ enum nfp_dumpspec_type {
struct nfp_dump_tl {
__be32 type;
__be32 length; /* chunk length to follow, aligned to 8 bytes */
- char data[0];
+ char data[];
};
/* NFP CPP parameters */
@@ -62,7 +62,7 @@ struct nfp_dumpspec_csr {
struct nfp_dumpspec_rtsym {
struct nfp_dump_tl tl;
- char rtsym[0];
+ char rtsym[];
};
/* header for register dumpable */
@@ -79,7 +79,7 @@ struct nfp_dump_rtsym {
struct nfp_dump_common_cpp cpp;
__be32 error; /* error code encountered while reading */
u8 padded_name_length; /* pad so data starts at 8 byte boundary */
- char rtsym[0];
+ char rtsym[];
/* after padded_name_length, there is dump_length data */
};
@@ -92,7 +92,7 @@ struct nfp_dump_error {
struct nfp_dump_tl tl;
__be32 error;
char padding[4];
- char spec[0];
+ char spec[];
};
/* to track state through debug size calculation TLV traversal */
diff --git a/drivers/net/ethernet/netronome/nfp/nfp_net_repr.h b/drivers/net/ethernet/netronome/nfp/nfp_net_repr.h
index e0f13dfe1f39..48a74accbbd3 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_net_repr.h
+++ b/drivers/net/ethernet/netronome/nfp/nfp_net_repr.h
@@ -18,7 +18,7 @@ struct nfp_port;
*/
struct nfp_reprs {
unsigned int num_reprs;
- struct net_device __rcu *reprs[0];
+ struct net_device __rcu *reprs[];
};
/**
diff --git a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp.h b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp.h
index 1531c1870020..f5360bae6f75 100644
--- a/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp.h
+++ b/drivers/net/ethernet/netronome/nfp/nfpcore/nfp_nsp.h
@@ -183,7 +183,7 @@ struct nfp_eth_table {
bool is_split;
unsigned int fec_modes_supported;
- } ports[0];
+ } ports[];
};
struct nfp_eth_table *nfp_eth_read_ports(struct nfp_cpp *cpp);
--
2.25.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH][next] netronome: Replace zero-length array with flexible-array member
2020-02-24 16:36 [PATCH][next] netronome: Replace zero-length array with flexible-array member Gustavo A. R. Silva
@ 2020-02-24 23:26 ` David Miller
0 siblings, 0 replies; 3+ messages in thread
From: David Miller @ 2020-02-24 23:26 UTC (permalink / raw)
To: gustavo
Cc: kuba, ast, daniel, kafai, songliubraving, yhs, andriin, netdev,
bpf, oss-drivers, linux-kernel
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Mon, 24 Feb 2020 10:36:52 -0600
> 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 <gustavo@embeddedor.com>
Applied.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH][next] netronome: Replace zero-length array with flexible-array member
@ 2020-02-24 17:25 Song Liu
0 siblings, 0 replies; 3+ messages in thread
From: Song Liu @ 2020-02-24 17:25 UTC (permalink / raw)
To: Gustavo A. R. Silva
Cc: Jakub Kicinski, David S. Miller, Alexei Starovoitov,
Daniel Borkmann, Martin Lau, Yonghong Song, Andrii Nakryiko,
netdev, bpf, oss-drivers, linux-kernel
> On Feb 24, 2020, at 8:34 AM, Gustavo A. R. Silva <gustavo@embeddedor.com> 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 <gustavo@embeddedor.com>
Acked-by: Song Liu <songliubraving@fb.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
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