diff options
| author | Gustavo A. R. Silva <gustavo@embeddedor.com> | 2020-02-26 18:17:44 -0600 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2020-02-28 01:21:02 +0100 |
| commit | d7f10df86202273155a9d8f8553bc2ad28e0dd46 (patch) | |
| tree | e253c06e6c409afbff1f057a5376fc77ac1dc01f /kernel | |
| parent | 4bc988464bb193d67c93ddb2fcd1de127d815b6c (diff) | |
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 'kernel')
| -rw-r--r-- | kernel/bpf/bpf_struct_ops.c | 2 | ||||
| -rw-r--r-- | kernel/bpf/hashtab.c | 2 | ||||
| -rw-r--r-- | kernel/bpf/lpm_trie.c | 2 |
3 files changed, 3 insertions, 3 deletions
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c index 042f95534f86..c498f0fffb40 100644 --- a/kernel/bpf/bpf_struct_ops.c +++ b/kernel/bpf/bpf_struct_ops.c @@ -23,7 +23,7 @@ enum bpf_struct_ops_state { struct bpf_struct_ops_value { BPF_STRUCT_OPS_COMMON_VALUE; - char data[0] ____cacheline_aligned_in_smp; + char data[] ____cacheline_aligned_in_smp; }; struct bpf_struct_ops_map { diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 53d9483fee10..d541c8486c95 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -118,7 +118,7 @@ struct htab_elem { struct bpf_lru_node lru_node; }; u32 hash; - char key[0] __aligned(8); + char key[] __aligned(8); }; static inline bool htab_is_prealloc(const struct bpf_htab *htab) diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c index 3b3c420bc8ed..65c236cf341e 100644 --- a/kernel/bpf/lpm_trie.c +++ b/kernel/bpf/lpm_trie.c @@ -25,7 +25,7 @@ struct lpm_trie_node { struct lpm_trie_node __rcu *child[2]; u32 prefixlen; u32 flags; - u8 data[0]; + u8 data[]; }; struct lpm_trie { |