binder: fix async space check for 0-sized buffers

commit 3091c21d3e9322428691ce0b7a0cfa9c0b239eeb upstream.

Move the padding of 0-sized buffers to an earlier stage to account for
this round up during the alloc->free_async_space check.

Fixes: 74310e06be4d ("android: binder: Move buffer out of area shared with user space")
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20231201172212.1813387-5-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 5e2505f..d2a6459 100644 (file)
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -407,6 +407,10 @@ static struct binder_buffer *binder_alloc_new_buf_locked(
                                alloc->pid, extra_buffers_size);
                return ERR_PTR(-EINVAL);
        }
+
+       /* Pad 0-size buffers so they get assigned unique addresses */
+       size = max(size, sizeof(void *));
+
        if (is_async &&
            alloc->free_async_space < size + sizeof(struct binder_buffer)) {
                binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC,
@@ -415,9 +419,6 @@ static struct binder_buffer *binder_alloc_new_buf_locked(
                return ERR_PTR(-ENOSPC);
        }
 
-       /* Pad 0-size buffers so they get assigned unique addresses */
-       size = max(size, sizeof(void *));
-
        while (n) {
                buffer = rb_entry(n, struct binder_buffer, rb_node);
                BUG_ON(!buffer->free);