fdt_region: Check return value of fdt_get_property_by_offset() calls

fdt_get_property_by_offset() returns NULL for FDT with version
less than 0x10. fdt_find_regions() dereferences the result without
checking, leading to a NULL pointer dereference during signature
verification of an untrusted FIT. fdt_add_alias_regions() and
fdt_next_region() also lack validation.

Add NULL checks before accessing the returned property pointer.
Also add a missing NULL check for fdt_string() in
fdt_add_alias_regions() and fdt_next_region().

Signed-off-by: Anton Ivanov <anton@binarly.io>

diff --git a/boot/fdt_region.c b/boot/fdt_region.c
index 295ea08ac91c622496351f6804da9e7cf0c4e3a5..0a9d47bb2bd3157ebe798d1cce00c537d8251683 100644 (file)
--- a/boot/fdt_region.c
+++ b/boot/fdt_region.c
@@ -69,6 +69,8 @@ int fdt_find_regions(const void *fdt, char * const inc[], int inc_count,
                        include = want >= 2;
                        stop_at = offset;
                        prop = fdt_get_property_by_offset(fdt, offset, NULL);
+                       if (!prop)
+                               return -FDT_ERR_BADSTRUCTURE;
                        str = fdt_string(fdt, fdt32_to_cpu(prop->nameoff));
                        if (!str)
                                return -FDT_ERR_BADSTRUCTURE;
@@ -271,7 +273,11 @@ int fdt_add_alias_regions(const void *fdt, struct fdt_region *region, int count,
                int target, next;
 
                prop = fdt_get_property_by_offset(fdt, offset, NULL);
+               if (!prop)
+                       return -FDT_ERR_BADSTRUCTURE;
                name = fdt_string(fdt, fdt32_to_cpu(prop->nameoff));
+               if (!name)
+                       return -FDT_ERR_BADSTRUCTURE;
                target = fdt_path_offset(fdt, name);
                if (!region_list_contains_offset(info, fdt, target))
                        continue;
@@ -520,7 +526,11 @@ int fdt_next_region(const void *fdt,
                case FDT_PROP:
                        stop_at = offset;
                        prop = fdt_get_property_by_offset(fdt, offset, NULL);
+                       if (!prop)
+                               return -FDT_ERR_BADSTRUCTURE;
                        str = fdt_string(fdt, fdt32_to_cpu(prop->nameoff));
+                       if (!str)
+                               return -FDT_ERR_BADSTRUCTURE;
                        val = h_include(priv, fdt, last_node, FDT_IS_PROP, str,
                                            strlen(str) + 1);
                        if (val == -1) {