bpf: Fix swapped arguments in calls to check_buffer_access

There are a couple of arguments of the boolean flag zero_size_allowed and
the char pointer buf_info when calling to function check_buffer_access that
are swapped by mistake. Fix these by swapping them to correct the argument
ordering.

Fixes: afbf21dc ("bpf: Support readonly/readwrite buffers in verifier")
Addresses-Coverity: ("Array compared to 0")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200727175411.155179-1-colin.king@canonical.com

kernel/bpf/verifier.c

@@ -3477,14 +3477,14 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
 				regno, reg_type_str[reg->type]);
 			return -EACCES;
 		}
-		err = check_buffer_access(env, reg, regno, off, size, "rdonly",
-					  false,
+		err = check_buffer_access(env, reg, regno, off, size, false,
+					  "rdonly",
 					  &env->prog->aux->max_rdonly_access);
 		if (!err && value_regno >= 0)
 			mark_reg_unknown(env, regs, value_regno);
 	} else if (reg->type == PTR_TO_RDWR_BUF) {
-		err = check_buffer_access(env, reg, regno, off, size, "rdwr",
-					  false,
+		err = check_buffer_access(env, reg, regno, off, size, false,
+					  "rdwr",
 					  &env->prog->aux->max_rdwr_access);
 		if (!err && t == BPF_READ && value_regno >= 0)
 			mark_reg_unknown(env, regs, value_regno);