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fdt_region: Check for a single root node of the correct name

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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 <sjg@chromium.org>
Reported-by: Bruce Monroe <bruce.monroe@intel.com>
Reported-by: Arie Haenel <arie.haenel@intel.com>
Reported-by: Julien Lenoir <julien.lenoir@intel.com>
This commit is contained in:
Simon Glass 2021-02-15 17:08:05 -07:00 committed by Tom Rini
parent 6144438fb5
commit 8a7d4cf982
1 changed files with 11 additions and 0 deletions
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11
common/fdt_region.c
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@ -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: