From: Simon Glass <sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
To: Devicetree Compiler
<devicetree-compiler-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Cc: David Gibson
<david-xT8FGy+AXnRB3Ne2BGzF6laj5H9X9Tb+@public.gmane.org>,
Simon Glass <sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
Arie Haenel <arie.haenel-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
Julien Lenoir
<julien.lenoir-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Subject: [PATCH v3 2/2] libfdt: Check that the root-node name is empty
Date: Tue, 23 Mar 2021 14:04:10 +1300 [thread overview]
Message-ID: <20210323010410.3222701-2-sjg@chromium.org> (raw)
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-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
Reported-by: Arie Haenel <arie.haenel-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Reported-by: Julien Lenoir <julien.lenoir-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
---
Changes in v3:
- Add to run_tests.sh also
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/run_tests.sh | 2 +-
tests/testdata.h | 1 +
tests/trees.S | 15 +++++++++++++++
6 files changed, 30 insertions(+), 3 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/run_tests.sh b/tests/run_tests.sh
index 82543fc..5c2b1e8 100755
--- a/tests/run_tests.sh
+++ b/tests/run_tests.sh
@@ -518,7 +518,7 @@ libfdt_tests () {
run_test check_full $good
done
for bad in truncated_property.dtb truncated_string.dtb \
- truncated_memrsv.dtb two_roots.dtb; do
+ truncated_memrsv.dtb two_roots.dtb named_root.dtb; do
run_test check_full -n $bad
done
}
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
next reply other threads:[~2021-03-23 1:04 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-23 1:04 Simon Glass [this message]
[not found] ` <20210323010410.3222701-2-sjg-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
2021-03-23 1:13 ` [PATCH v3 2/2] libfdt: Check that the root-node name is empty David Gibson
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