io_uring/query: buffer size calculations with a union

Instead of having an array of a calculated size as a buffer, put all
query uapi structures into a union and pass that around. That way
everything is well typed, and the compiler will prevent opcode handling
using a structure not accounted into the buffer size.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/query.c b/io_uring/query.c
index 645301bd2c8293184b77aa0d357c525d65c6462f..6cf732936b3d7a83520ae841592f35556aa15938 100644 (file)
--- a/io_uring/query.c
+++ b/io_uring/query.c
@@ -5,14 +5,16 @@
 #include "query.h"
 #include "io_uring.h"
 
-#define IO_MAX_QUERY_SIZE              (sizeof(struct io_uring_query_opcode))
+union io_query_data {
+       struct io_uring_query_opcode opcodes;
+};
+
+#define IO_MAX_QUERY_SIZE              sizeof(union io_query_data)
 #define IO_MAX_QUERY_ENTRIES           1000
 
-static ssize_t io_query_ops(void *data)
+static ssize_t io_query_ops(union io_query_data *data)
 {
-       struct io_uring_query_opcode *e = data;
-
-       BUILD_BUG_ON(sizeof(*e) > IO_MAX_QUERY_SIZE);
+       struct io_uring_query_opcode *e = &data->opcodes;
 
        e->nr_request_opcodes = IORING_OP_LAST;
        e->nr_register_opcodes = IORING_REGISTER_LAST;
@@ -24,7 +26,7 @@ static ssize_t io_query_ops(void *data)
 }
 
 static int io_handle_query_entry(struct io_ring_ctx *ctx,
-                                void *data, void __user *uhdr,
+                                union io_query_data *data, void __user *uhdr,
                                 u64 *next_entry)
 {
        struct io_uring_query_hdr hdr;
@@ -73,11 +75,11 @@ out:
 
 int io_query(struct io_ring_ctx *ctx, void __user *arg, unsigned nr_args)
 {
-       char entry_buffer[IO_MAX_QUERY_SIZE];
+       union io_query_data entry_buffer;
        void __user *uhdr = arg;
        int ret, nr = 0;
 
-       memset(entry_buffer, 0, sizeof(entry_buffer));
+       memset(&entry_buffer, 0, sizeof(entry_buffer));
 
        if (nr_args)
                return -EINVAL;
@@ -85,7 +87,7 @@ int io_query(struct io_ring_ctx *ctx, void __user *arg, unsigned nr_args)
        while (uhdr) {
                u64 next_hdr;
 
-               ret = io_handle_query_entry(ctx, entry_buffer, uhdr, &next_hdr);
+               ret = io_handle_query_entry(ctx, &entry_buffer, uhdr, &next_hdr);
                if (ret)
                        return ret;
                uhdr = u64_to_user_ptr(next_hdr);