io_uring/kbuf: check for buffer list readiness after NULL check

Move the buffer list 'is_ready' check below the validity check for
the buffer list for a given group.

Fixes: 5cf4f52e6d8a ("io_uring: free io_buffer_list entries via RCU")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c
index bd25bc2deeaf837bc3f34ec69984722ea7b39052..72b6af1d2ed3b0fc7cf629608173f750cb487247 100644 (file)
--- a/io_uring/kbuf.c
+++ b/io_uring/kbuf.c
@@ -756,6 +756,8 @@ void *io_pbuf_get_address(struct io_ring_ctx *ctx, unsigned long bgid)
 
        bl = __io_buffer_get_list(ctx, smp_load_acquire(&ctx->io_bl), bgid);
 
+       if (!bl || !bl->is_mmap)
+               return NULL;
        /*
         * Ensure the list is fully setup. Only strictly needed for RCU lookup
         * via mmap, and in that case only for the array indexed groups. For
@@ -763,8 +765,6 @@ void *io_pbuf_get_address(struct io_ring_ctx *ctx, unsigned long bgid)
         */
        if (!smp_load_acquire(&bl->is_ready))
                return NULL;
-       if (!bl || !bl->is_mmap)
-               return NULL;
 
        return bl->buf_ring;
 }