On 4/30/20 11:30 PM, Arnd Bergmann wrote:
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>
Not pretty but looks okay to me, both have the same offset afterwards
in the pahole dump as well.
struct bpf_prog {
[...]
unsigned int (*bpf_func)(const void *, const struct bpf_insn *); /* 48 8 */
struct sock_filter insns[0]; /* 56 0 */
struct bpf_insn insnsi[]; /* 56 0 */
/* size: 56, cachelines: 1, members: 21 */
/* sum members: 50, holes: 1, sum holes: 4 */
/* sum bitfield members: 10 bits, bit holes: 1, sum bit holes: 6 bits */
/* last cacheline: 56 bytes */
};
Applied to bpf-next, thanks!
