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fdt: break loop compatibles when no NUL-terminator is found #807

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fdt: break loop compatibles when no NUL-terminator is found #807

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4 changes: 4 additions & 0 deletions src/fdt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -737,6 +737,10 @@ int fdt_node_offset_by_compatible(const void *fdt, int startoffset,
len -= (nextprop - prop) + 1;
prop = nextprop + 1;
}
else {
/* No NUL terminator within the declared length, break. */
break;
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}
}
}
return offset;
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54 changes: 54 additions & 0 deletions tools/unit-tests/unit-fdt.c
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Expand Up @@ -157,17 +157,71 @@ START_TEST(test_fdt_shrink_rejects_dt_strings_area_overflow)
}
END_TEST

/* Minimal FDT whose root node carries a `compatible` property whose value has
* no NUL terminator within its declared length (len=4, "AAAA").
* fdt_node_offset_by_compatible() walks the (possibly multi-string) compatible
* value with memchr(prop, '\0', len); */
static const uint8_t fdt_compatible_no_terminator[] = {
/* header */
0xd0, 0x0d, 0xfe, 0xed, /* magic */
0x00, 0x00, 0x00, 0x63, /* totalsize = 99 */
0x00, 0x00, 0x00, 0x38, /* off_dt_struct = 56 */
0x00, 0x00, 0x00, 0x58, /* off_dt_strings = 88 */
0x00, 0x00, 0x00, 0x28, /* off_mem_rsvmap = 40 */
0x00, 0x00, 0x00, 0x11, /* version = 17 */
0x00, 0x00, 0x00, 0x10, /* last_comp_version = 16 */
0x00, 0x00, 0x00, 0x00, /* boot_cpuid_phys */
0x00, 0x00, 0x00, 0x0b, /* size_dt_strings = 11 */
0x00, 0x00, 0x00, 0x20, /* size_dt_struct = 32 */
/* mem_rsvmap terminator (offset 40) */
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
/* struct block (offset 56) */
0x00, 0x00, 0x00, 0x01, /* BEGIN_NODE root */
0x00, 0x00, 0x00, 0x00, /* "" */
0x00, 0x00, 0x00, 0x03, /* FDT_PROP */
0x00, 0x00, 0x00, 0x04, /* len = 4 */
0x00, 0x00, 0x00, 0x00, /* nameoff = 0 ("compatible") */
0x41, 0x41, 0x41, 0x41, /* value "AAAA" -- no NUL */
0x00, 0x00, 0x00, 0x02, /* END_NODE root */
0x00, 0x00, 0x00, 0x09, /* FDT_END */
/* strings block (offset 88) */
0x63, 0x6f, 0x6d, 0x70, 0x61, 0x74, 0x69, 0x62, /* "compatib" */
0x6c, 0x65, 0x00, /* "le\0" */
};

START_TEST(test_fdt_node_offset_by_compatible_terminates_on_unterminated_prop)
{
int off;

/* complen = strlen("foo") = 3 <= 4 = declared property length, so the
* inner walk loop is entered; "foo" != "AAAA" so it does not match and
* falls through to the memchr() advance */
off = fdt_node_offset_by_compatible(fdt_compatible_no_terminator, -1, "foo");

ck_assert_int_lt(off, 0);
}
END_TEST

static Suite *fdt_suite(void)
{
Suite *s = suite_create("fdt");
TCase *tc = tcase_create("fdt");
/* Separate case with a hard timeout so an unterminated-property
* regression is reported as a failure rather than hanging the suite. */
TCase *tc_dos = tcase_create("fdt-dos");

tcase_add_test(tc, test_fdt_get_string_rejects_out_of_range_offset);
tcase_add_test(tc, test_fdt_get_string_returns_string_with_valid_offset);
tcase_add_test(tc, test_fit_load_image_rejects_oversized_prop_len);
tcase_add_test(tc, test_fdt_shrink_rejects_dt_strings_area_overflow);
suite_add_tcase(s, tc);

tcase_set_timeout(tc_dos, 5);
tcase_add_test(tc_dos,
test_fdt_node_offset_by_compatible_terminates_on_unterminated_prop);
suite_add_tcase(s, tc_dos);

return s;
}

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