linux-kernel - [084/121] of: fdt: fix memory initialization for expanded DT

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Message-ID: <lsq.1378608721.145739295@decadent.org.uk>
Date:	Sun, 08 Sep 2013 03:52:01 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Alexander Sverdlin" <alexander.sverdlin@....com>,
	"Rob Herring" <rob.herring@...xeda.com>,
	"Wladislav Wiebe" <wladislav.kw@...il.com>
Subject: [084/121] of: fdt: fix memory initialization for expanded DT

3.2.51-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Wladislav Wiebe <wladislav.kw@...il.com>

commit 9e40127526e857fa3f29d51e83277204fbdfc6ba upstream.

Already existing property flags are filled wrong for properties created from
initial FDT. This could cause problems if this DYNAMIC device-tree functions
are used later, i.e. properties are attached/detached/replaced. Simply dumping
flags from the running system show, that some initial static (not allocated via
kzmalloc()) nodes are marked as dynamic.

I putted some debug extensions to property_proc_show(..) :
..
+       if (OF_IS_DYNAMIC(pp))
+               pr_err("DEBUG: xxx : OF_IS_DYNAMIC\n");
+       if (OF_IS_DETACHED(pp))
+               pr_err("DEBUG: xxx : OF_IS_DETACHED\n");

when you operate on the nodes (e.g.: ~$ cat /proc/device-tree/*some_node*) you
will see that those flags are filled wrong, basically in most cases it will dump
a DYNAMIC or DETACHED status, which is in not true.
(BTW. this OF_IS_DETACHED is a own define for debug purposes which which just
make a test_bit(OF_DETACHED, &x->_flags)

If nodes are dynamic kernel is allowed to kfree() them. But it will crash
attempting to do so on the nodes from FDT -- they are not allocated via
kzmalloc().

Signed-off-by: Wladislav Wiebe <wladislav.kw@...il.com>
Acked-by: Alexander Sverdlin <alexander.sverdlin@....com>
Signed-off-by: Rob Herring <rob.herring@...xeda.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/of/fdt.c | 2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -389,6 +389,8 @@ static void __unflatten_device_tree(stru
 	mem = (unsigned long)
 		dt_alloc(size + 4, __alignof__(struct device_node));

+	memset((void *)mem, 0, size);
+
 	((__be32 *)mem)[size / 4] = cpu_to_be32(0xdeadbeef);

 	pr_debug("  unflattening %lx...\n", mem);

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