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@xxxxxxxxxxxx>
Reported-by: Arie Haenel <arie.haenel@xxxxxxxxx>
Reported-by: Julien Lenoir <julien.lenoir@xxxxxxxxx>
---
Changes in v2:
- Use FDT_ERR_BADSTRUCTURE instead of FDT_ERR_BADLAYOUT
libfdt/fdt_check.c | 10 ++++++++++
tests/Makefile.tests | 2 +-
tests/dumptrees.c | 3 ++-
tests/testdata.h | 1 +
tests/trees.S | 15 +++++++++++++++
5 files changed, 29 insertions(+), 2 deletions(-)
diff --git a/libfdt/fdt_check.c b/libfdt/fdt_check.c
index 13595a2..fa410a8 100644
--- a/libfdt/fdt_check.c
+++ b/libfdt/fdt_check.c
@@ -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:
diff --git a/tests/Makefile.tests b/tests/Makefile.tests
index fe5cae8..2b47627 100644
--- a/tests/Makefile.tests
+++ b/tests/Makefile.tests
@@ -33,7 +33,7 @@ LIB_TESTS_L = get_mem_rsv \
LIB_TESTS = $(LIB_TESTS_L:%=$(TESTS_PREFIX)%)
LIBTREE_TESTS_L = truncated_property truncated_string truncated_memrsv \
- two_roots
+ two_roots named_root
LIBTREE_TESTS = $(LIBTREE_TESTS_L:%=$(TESTS_PREFIX)%)
diff --git a/tests/dumptrees.c b/tests/dumptrees.c
index 02ca092..f1e0ea9 100644
--- a/tests/dumptrees.c
+++ b/tests/dumptrees.c
@@ -24,7 +24,8 @@ static struct {
TREE(ovf_size_strings),
TREE(truncated_property), TREE(truncated_string),
TREE(truncated_memrsv),
- TREE(two_roots)
+ TREE(two_roots),
+ TREE(named_root)
};
#define NUM_TREES (sizeof(trees) / sizeof(trees[0]))
diff --git a/tests/testdata.h b/tests/testdata.h
index d03f352..4f9e3ba 100644
--- a/tests/testdata.h
+++ b/tests/testdata.h
@@ -56,4 +56,5 @@ extern struct fdt_header ovf_size_strings;
extern struct fdt_header truncated_string;
extern struct fdt_header truncated_memrsv;
extern struct fdt_header two_roots;
+extern struct fdt_header named_root;
#endif /* ! __ASSEMBLY */
diff --git a/tests/trees.S b/tests/trees.S
index e2380b7..95d599d 100644
--- a/tests/trees.S
+++ b/tests/trees.S
@@ -298,3 +298,18 @@ two_roots_strings_end:
two_roots_end:
+
+ /* root node with a non-empty name */
+ TREE_HDR(named_root)
+ EMPTY_RSVMAP(named_root)
+
+named_root_struct:
+ BEGIN_NODE("fake")
+ END_NODE
+ FDTLONG(FDT_END)
+named_root_struct_end:
+
+named_root_strings:
+named_root_strings_end:
+
+named_root_end:
--
2.31.0.rc2.261.g7f71774620-goog
