linux-kernel - [PATCH v2 04/28] binder: fix async space check for 0-sized buffers

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Date:   Fri,  1 Dec 2023 17:21:33 +0000
From:   Carlos Llamas <cmllamas@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Arve Hjønnevåg" <arve@...roid.com>,
        Todd Kjos <tkjos@...roid.com>,
        Martijn Coenen <maco@...roid.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Christian Brauner <brauner@...nel.org>,
        Carlos Llamas <cmllamas@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Sherry Yang <sherryy@...roid.com>
Cc:     linux-kernel@...r.kernel.org, kernel-team@...roid.com,
        Alice Ryhl <aliceryhl@...gle.com>
Subject: [PATCH v2 04/28] binder: fix async space check for 0-sized buffers

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@...gle.com>
Signed-off-by: Carlos Llamas <cmllamas@...gle.com>
---
 drivers/android/binder_alloc.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index adcec5ec0959..abff1bafcc43 100644
--- 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);
-- 
2.43.0.rc2.451.g8631bc7472-goog