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libfdt: Check for multiple/invalid root nodes 

It is possible to construct a devicetree blob with multiple root nodes.
Update fdt_check_full() to check for this, along with a root node with an
invalid name.

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 17:08:11 -07:00 committed by Tom Rini
parent 6f3c2d8aa5
commit 124c255731
2 changed files with 19 additions and 1 deletions
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17
scripts/dtc/libfdt/fdt_ro.c
View File

@ -867,6 +867,7 @@ int fdt_check_full(const void *fdt, size_t bufsize)
unsigned depth = 0;
const void *prop;
const char *propname;
bool expect_end = false;
if (bufsize < FDT_V1_SIZE)
return -FDT_ERR_TRUNCATED;
@ -887,6 +888,10 @@ int fdt_check_full(const void *fdt, size_t bufsize)
if (nextoffset < 0)
return nextoffset;
/* If we see two root nodes, something is wrong */
if (expect_end && tag != FDT_END)
return -FDT_ERR_BADLAYOUT;
switch (tag) {
case FDT_NOP:
break;
@ -900,12 +905,24 @@ 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_BADLAYOUT;
}
break;
case FDT_END_NODE:
if (depth == 0)
return -FDT_ERR_BADSTRUCTURE;
depth--;
if (depth == 0)
expect_end = true;
break;
case FDT_PROP:

3
test/py/tests/test_vboot.py
View File

@ -255,7 +255,8 @@ def test_vboot(u_boot_console, sha_algo, padding, sign_options, required,
util.run_and_log_expect_exception(
cons, [fit_check_sign, '-f', efit, '-k', dtb],
1, 'Failed to verify required signature')
run_bootm(sha_algo, 'evil fakeroot', 'Bad Data Hash', False, efit)
run_bootm(sha_algo, 'evil fakeroot', 'Bad FIT kernel image format',
False, efit)
# Try adding an @ to the kernel node name. This should be detected.
efit = '%stest.evilk.fit' % tmpdir