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libfdt: Check that the root-node name is empty

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The root node is supposed to have an empty name, but at present this is
not checked. The behaviour of such a tree is not well defined. Most
software rightly assumes that the root node is at offset 0 and does not
check the name. This oddity was discovered as part of a security
investigation into U-Boot verified boot.

Add a check for this to fdt_check_full().

Signed-off-by: Simon Glass <sjg@chromium.org>
Reported-by: Arie Haenel <arie.haenel@intel.com>
Reported-by: Julien Lenoir <julien.lenoir@intel.com>
Message-Id: <20210323010410.3222701-2-sjg@chromium.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Simon Glass 2021-03-23 14:04:10 +13:00 • committed by David Gibson
parent 4ca61f84dc
commit a2def54799
6 changed files with 30 additions and 3 deletions
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10
libfdt/fdt_check.c
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@ -59,6 +59,16 @@ int fdt_check_full(const void *fdt, size_t bufsize)
depth++;
if (depth > INT_MAX)
return -FDT_ERR_BADSTRUCTURE;
/* The root node must have an empty name */
if (depth == 1) {
const char *name;
int len;
name = fdt_get_name(fdt, offset, &len);
if (*name || len)
return -FDT_ERR_BADSTRUCTURE;
}
break;
case FDT_END_NODE: