At present fdt_find_regions() assumes that the FIT is a valid devicetree.
If the FIT has two root nodes this is currently not detected in this
function, nor does libfdt's fdt_check_full() notice. Also it is possible
for the root node to have a name even though it should not.
Add checks for these and return -FDT_ERR_BADSTRUCTURE if a problem is
detected.
CVE-2021-27097
Signed-off-by: Simon Glass <s...@chromium.org>
Reported-by: Bruce Monroe <bruce.mon...@intel.com>
Reported-by: Arie Haenel <arie.hae...@intel.com>
Reported-by: Julien Lenoir <julien.len...@intel.com>
---
common/fdt_region.c | 11 +++++++++++
1 file changed, 11 insertions(+)
diff --git a/common/fdt_region.c b/common/fdt_region.c
index ff12c518e97..e4ef0ca7703 100644
--- a/common/fdt_region.c
+++ b/common/fdt_region.c
@@ -43,6 +43,7 @@ int fdt_find_regions(const void *fdt, char * const inc[], int
inc_count,
int depth = -1;
int want = 0;
int base = fdt_off_dt_struct(fdt);
+ bool expect_end = false;
end = path;
*end = '\0';
@@ -59,6 +60,10 @@ int fdt_find_regions(const void *fdt, char * const inc[],
int inc_count,
tag = fdt_next_tag(fdt, offset, &nextoffset);
stop_at = nextoffset;
+ /* If we see two root nodes, something is wrong */
+ if (expect_end && tag != FDT_END)
+ return -FDT_ERR_BADLAYOUT;
+
switch (tag) {
case FDT_PROP:
include = want >= 2;
@@ -81,6 +86,10 @@ int fdt_find_regions(const void *fdt, char * const inc[],
int inc_count,
if (depth == FDT_MAX_DEPTH)
return -FDT_ERR_BADSTRUCTURE;
name = fdt_get_name(fdt, offset, &len);
+
+ /* The root node must have an empty name */
+ if (!depth && *name)
+ return -FDT_ERR_BADLAYOUT;
if (end - path + 2 + len >= path_len)
return -FDT_ERR_NOSPACE;
if (end != path + 1)
@@ -108,6 +117,8 @@ int fdt_find_regions(const void *fdt, char * const inc[],
int inc_count,
while (end > path && *--end != '/')
;
*end = '\0';
+ if (depth == -1)
+ expect_end = true;
break;
case FDT_END:
--
2.30.0.478.g8a0d178c01-goog
