bpf: Add struct for bin_args arg in bpf_bprintf_prepare

Adding struct bpf_bprintf_data to hold bin_args argument for
bpf_bprintf_prepare function.

We will add another return argument to bpf_bprintf_prepare and
pass the struct to bpf_bprintf_cleanup for proper cleanup in
following changes.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20221215214430.1336195-2-jolsa@kernel.org

2 files changed, 15 insertions, 12 deletions

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index af30c6cbd65d..7dbf6bb72cad 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -798,16 +798,16 @@ void bpf_bprintf_cleanup(void)
  * Returns a negative value if fmt is an invalid format string or 0 otherwise.
  *
  * This can be used in two ways:
- * - Format string verification only: when bin_args is NULL
+ * - Format string verification only: when data->get_bin_args is false
  * - Arguments preparation: in addition to the above verification, it writes in
- *   bin_args a binary representation of arguments usable by bstr_printf where
- *   pointers from BPF have been sanitized.
+ *   data->bin_args a binary representation of arguments usable by bstr_printf
+ *   where pointers from BPF have been sanitized.
  *
  * In argument preparation mode, if 0 is returned, safe temporary buffers are
  * allocated and bpf_bprintf_cleanup should be called to free them after use.
  */
 int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
-			u32 **bin_args, u32 num_args)
+			u32 num_args, struct bpf_bprintf_data *data)
 {
 	char *unsafe_ptr = NULL, *tmp_buf = NULL, *tmp_buf_end, *fmt_end;
 	size_t sizeof_cur_arg, sizeof_cur_ip;
@@ -820,12 +820,12 @@ int bpf_bprintf_prepare(char *fmt, u32 fmt_size, const u64 *raw_args,
 		return -EINVAL;
 	fmt_size = fmt_end - fmt;
 
-	if (bin_args) {
+	if (data->get_bin_args) {
 		if (num_args && try_get_fmt_tmp_buf(&tmp_buf))
 			return -EBUSY;
 
 		tmp_buf_end = tmp_buf + MAX_BPRINTF_BUF_LEN;
-		*bin_args = (u32 *)tmp_buf;
+		data->bin_args = (u32 *)tmp_buf;
 	}
 
 	for (i = 0; i < fmt_size; i++) {
@@ -1026,24 +1026,26 @@ out:
 }
 
 BPF_CALL_5(bpf_snprintf, char *, str, u32, str_size, char *, fmt,
-	   const void *, data, u32, data_len)
+	   const void *, args, u32, data_len)
 {
+	struct bpf_bprintf_data data = {
+		.get_bin_args	= true,
+	};
 	int err, num_args;
-	u32 *bin_args;
 
 	if (data_len % 8 || data_len > MAX_BPRINTF_VARARGS * 8 ||
-	    (data_len && !data))
+	    (data_len && !args))
 		return -EINVAL;
 	num_args = data_len / 8;
 
 	/* ARG_PTR_TO_CONST_STR guarantees that fmt is zero-terminated so we
 	 * can safely give an unbounded size.
 	 */
-	err = bpf_bprintf_prepare(fmt, UINT_MAX, data, &bin_args, num_args);
+	err = bpf_bprintf_prepare(fmt, UINT_MAX, args, num_args, &data);
 	if (err < 0)
 		return err;
 
-	err = bstr_printf(str, str_size, fmt, bin_args);
+	err = bstr_printf(str, str_size, fmt, data.bin_args);
 
 	bpf_bprintf_cleanup();
 
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index a5255a0dcbb6..faa358b3d5d7 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7612,6 +7612,7 @@ static int check_bpf_snprintf_call(struct bpf_verifier_env *env,
 	struct bpf_reg_state *fmt_reg = &regs[BPF_REG_3];
 	struct bpf_reg_state *data_len_reg = &regs[BPF_REG_5];
 	struct bpf_map *fmt_map = fmt_reg->map_ptr;
+	struct bpf_bprintf_data data = {};
 	int err, fmt_map_off, num_args;
 	u64 fmt_addr;
 	char *fmt;
@@ -7636,7 +7637,7 @@ static int check_bpf_snprintf_call(struct bpf_verifier_env *env,
 	/* We are also guaranteed that fmt+fmt_map_off is NULL terminated, we
 	 * can focus on validating the format specifiers.
 	 */
-	err = bpf_bprintf_prepare(fmt, UINT_MAX, NULL, NULL, num_args);
+	err = bpf_bprintf_prepare(fmt, UINT_MAX, NULL, num_args, &data);
 	if (err < 0)
 		verbose(env, "Invalid format string\n");