[PATCH 1/1] of: fdt: fix memory initialization for expanded DT

From: Wladislav Wiebe
Date: Mon Aug 12 2013 - 07:02:10 EST

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

Signed-off-by: Wladislav Wiebe <wladislav.kw@xxxxxxxxx>
drivers/of/fdt.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 6bb7cf2..b10ba00 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -392,6 +392,8 @@ static void __unflatten_device_tree(struct boot_param_header *blob,
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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