scmp_bpf_sim: fix aliasing UB

See #425.

Punning sys_data_b between uint32_t* and struct* seccomp_data isn't legal,
use memcpy to fix the testsuite with Clang 17.

Modern compilers recognise this idiom and optimise it out anyway.

Signed-off-by: Sam James <[email protected]>
Acked-by: Tom Hromatka <[email protected]>
Signed-off-by: Paul Moore <[email protected]>

Author: thesamesam

tools/scmp_bpf_sim.c

@@ -182,7 +182,8 @@ static void bpf_execute(const struct bpf_program *prg,
 		switch (code) {
 		case BPF_LD+BPF_W+BPF_ABS:
 			if (k < BPF_SYSCALL_MAX) {
-				uint32_t val = *((uint32_t *)&sys_data_b[k]);
+				uint32_t val;
+				memcpy(&val, &sys_data_b[k], sizeof(val));
 				state.acc = ttoh32(arch, val);
 			} else
 				exit_error(ERANGE, ip_c);