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author | Gustavo A. R. Silva <gustavo@embeddedor.com> | 2020-02-26 18:17:44 -0600 |
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committer | Daniel Borkmann <daniel@iogearbox.net> | 2020-02-28 01:21:02 +0100 |
commit | d7f10df86202273155a9d8f8553bc2ad28e0dd46 (patch) | |
tree | e253c06e6c409afbff1f057a5376fc77ac1dc01f /include/linux/bpf.h | |
parent | 4bc988464bb193d67c93ddb2fcd1de127d815b6c (diff) | |
download | lwn-d7f10df86202273155a9d8f8553bc2ad28e0dd46.tar.gz lwn-d7f10df86202273155a9d8f8553bc2ad28e0dd46.zip |
bpf: 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")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20200227001744.GA3317@embeddedor
Diffstat (limited to 'include/linux/bpf.h')
-rw-r--r-- | include/linux/bpf.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 1acd5bf70350..9aa33b8f3d55 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -859,7 +859,7 @@ struct bpf_prog_array_item { struct bpf_prog_array { struct rcu_head rcu; - struct bpf_prog_array_item items[0]; + struct bpf_prog_array_item items[]; }; struct bpf_prog_array *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags); |