linux-kernel - [PATCH] kdbus: fix wrong message size on 32bit

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Date:	Fri, 24 Jul 2015 12:32:09 +0200
From:	David Herrmann <dh.herrmann@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Daniel Mack <daniel@...que.org>,
	Djalal Harouni <tixxdz@...ndz.org>,
	Alban Browaeys <prahal@...oo.com>,
	David Herrmann <dh.herrmann@...il.com>
Subject: [PATCH] kdbus: fix wrong message size on 32bit

When broadcasting messages, each receiver might get a different message
due to different metadata requirements. Therefore, the value of msg->size
might be different for each receiver. To account for that, we use a
temporary variable to store the real size and use it as source for the
iovec-copy transaction instead of &msg->size.

But we incorrectly used "size_t" for this variable. Hence, on 32bit, we
end up missing 4 bytes of the message header as "size_t" might only be
32bit wide.

Fix this and properly use "u64" for the message size that is copied to
user-space.

Reported-by: Alban Browaeys <prahal@...oo.com>
Signed-off-by: David Herrmann <dh.herrmann@...il.com>
---
 ipc/kdbus/message.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ipc/kdbus/message.c b/ipc/kdbus/message.c
index 27a5021..432dba4 100644
--- a/ipc/kdbus/message.c
+++ b/ipc/kdbus/message.c
@@ -886,9 +886,9 @@ struct kdbus_pool_slice *kdbus_staging_emit(struct kdbus_staging *staging,
 {
 	struct kdbus_item *item, *meta_items = NULL;
 	struct kdbus_pool_slice *slice = NULL;
-	size_t off, size, msg_size, meta_size;
+	size_t off, size, meta_size;
 	struct iovec *v;
-	u64 attach;
+	u64 attach, msg_size;
 	int ret;

 	/*
-- 
2.4.6

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