gcc-10 warns about accesses to zero-length arrays:
kernel/bpf/core.c: In function 'bpf_patch_insn_single':
cc1: warning: writing 8 bytes into a region of size 0 [-Wstringop-overflow=]
In file included from kernel/bpf/core.c:21:
include/linux/filter.h:550:20: note: at offset 0 to object 'insnsi' with size 0 declared here
550 | struct bpf_insn insnsi[0];
| ^~~~~~
In this case, we really want to have two flexible-array members,
but that is not possible. Removing the union to make insnsi a
flexible-array member while leaving insns as a zero-length array
fixes the warning, as nothing writes to the other one in that way.
This trick only works on linux-3.18 or higher, as older versions
had additional members in the union.
Fixes: 60a3b2253c41 ("net: bpf: make eBPF interpreter images read-only")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
include/linux/filter.h | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index af37318bb1c5..73d06a39e2d6 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -545,10 +545,8 @@ struct bpf_prog {
unsigned int (*bpf_func)(const void *ctx,
const struct bpf_insn *insn);
/* Instructions for interpreter */
- union {
- struct sock_filter insns[0];
- struct bpf_insn insnsi[0];
- };
+ struct sock_filter insns[0];
+ struct bpf_insn insnsi[];
};
struct sk_filter {
--
2.26.0
