of: Fix overflow bug in string property parsing functions

The string property read helpers will run off the end of the buffer if
it is handed a malformed string property. Rework the parsers to make
sure that doesn't happen. At the same time add new test cases to make
sure the functions behave themselves.

The original implementations of of_property_read_string_index() and
of_property_count_strings() both open-coded the same block of parsing
code, each with it's own subtly different bugs. The fix here merges
functions into a single helper and makes the original functions static
inline wrappers around the helper.

One non-bugfix aspect of this patch is the addition of a new wrapper,
of_property_read_string_array(). The new wrapper is needed by the
device_properties feature that Rafael is working on and planning to
merge for v3.19. The implementation is identical both with and without
the new static inline wrapper, so it just got left in to reduce the
churn on the header file.

Signed-off-by: Grant Likely <grant.likely@linaro.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Darren Hart <darren.hart@intel.com>
Cc: <stable@vger.kernel.org>  # v3.3+: Drop selftest hunks that don't apply

1 files changed, 60 insertions, 6 deletions

diff --git a/drivers/of/selftest.c b/drivers/of/selftest.c
index 7800127..11b873c 100644
--- a/drivers/of/selftest.c
+++ b/drivers/of/selftest.c
@@ -339,8 +339,9 @@ static void __init of_selftest_parse_phandle_with_args(void)
 	selftest(rc == -EINVAL, "expected:%i got:%i\n", -EINVAL, rc);
 }
 
-static void __init of_selftest_property_match_string(void)
+static void __init of_selftest_property_string(void)
 {
+	const char *strings[4];
 	struct device_node *np;
 	int rc;
 
@@ -357,13 +358,66 @@ static void __init of_selftest_property_match_string(void)
 	rc = of_property_match_string(np, "phandle-list-names", "third");
 	selftest(rc == 2, "third expected:0 got:%i\n", rc);
 	rc = of_property_match_string(np, "phandle-list-names", "fourth");
-	selftest(rc == -ENODATA, "unmatched string; rc=%i", rc);
+	selftest(rc == -ENODATA, "unmatched string; rc=%i\n", rc);
 	rc = of_property_match_string(np, "missing-property", "blah");
-	selftest(rc == -EINVAL, "missing property; rc=%i", rc);
+	selftest(rc == -EINVAL, "missing property; rc=%i\n", rc);
 	rc = of_property_match_string(np, "empty-property", "blah");
-	selftest(rc == -ENODATA, "empty property; rc=%i", rc);
+	selftest(rc == -ENODATA, "empty property; rc=%i\n", rc);
 	rc = of_property_match_string(np, "unterminated-string", "blah");
-	selftest(rc == -EILSEQ, "unterminated string; rc=%i", rc);
+	selftest(rc == -EILSEQ, "unterminated string; rc=%i\n", rc);
+
+	/* of_property_count_strings() tests */
+	rc = of_property_count_strings(np, "string-property");
+	selftest(rc == 1, "Incorrect string count; rc=%i\n", rc);
+	rc = of_property_count_strings(np, "phandle-list-names");
+	selftest(rc == 3, "Incorrect string count; rc=%i\n", rc);
+	rc = of_property_count_strings(np, "unterminated-string");
+	selftest(rc == -EILSEQ, "unterminated string; rc=%i\n", rc);
+	rc = of_property_count_strings(np, "unterminated-string-list");
+	selftest(rc == -EILSEQ, "unterminated string array; rc=%i\n", rc);
+
+	/* of_property_read_string_index() tests */
+	rc = of_property_read_string_index(np, "string-property", 0, strings);
+	selftest(rc == 0 && !strcmp(strings[0], "foobar"), "of_property_read_string_index() failure; rc=%i\n", rc);
+	strings[0] = NULL;
+	rc = of_property_read_string_index(np, "string-property", 1, strings);
+	selftest(rc == -ENODATA && strings[0] == NULL, "of_property_read_string_index() failure; rc=%i\n", rc);
+	rc = of_property_read_string_index(np, "phandle-list-names", 0, strings);
+	selftest(rc == 0 && !strcmp(strings[0], "first"), "of_property_read_string_index() failure; rc=%i\n", rc);
+	rc = of_property_read_string_index(np, "phandle-list-names", 1, strings);
+	selftest(rc == 0 && !strcmp(strings[0], "second"), "of_property_read_string_index() failure; rc=%i\n", rc);
+	rc = of_property_read_string_index(np, "phandle-list-names", 2, strings);
+	selftest(rc == 0 && !strcmp(strings[0], "third"), "of_property_read_string_index() failure; rc=%i\n", rc);
+	strings[0] = NULL;
+	rc = of_property_read_string_index(np, "phandle-list-names", 3, strings);
+	selftest(rc == -ENODATA && strings[0] == NULL, "of_property_read_string_index() failure; rc=%i\n", rc);
+	strings[0] = NULL;
+	rc = of_property_read_string_index(np, "unterminated-string", 0, strings);
+	selftest(rc == -EILSEQ && strings[0] == NULL, "of_property_read_string_index() failure; rc=%i\n", rc);
+	rc = of_property_read_string_index(np, "unterminated-string-list", 0, strings);
+	selftest(rc == 0 && !strcmp(strings[0], "first"), "of_property_read_string_index() failure; rc=%i\n", rc);
+	strings[0] = NULL;
+	rc = of_property_read_string_index(np, "unterminated-string-list", 2, strings); /* should fail */
+	selftest(rc == -EILSEQ && strings[0] == NULL, "of_property_read_string_index() failure; rc=%i\n", rc);
+	strings[1] = NULL;
+
+	/* of_property_read_string_array() tests */
+	rc = of_property_read_string_array(np, "string-property", strings, 4);
+	selftest(rc == 1, "Incorrect string count; rc=%i\n", rc);
+	rc = of_property_read_string_array(np, "phandle-list-names", strings, 4);
+	selftest(rc == 3, "Incorrect string count; rc=%i\n", rc);
+	rc = of_property_read_string_array(np, "unterminated-string", strings, 4);
+	selftest(rc == -EILSEQ, "unterminated string; rc=%i\n", rc);
+	/* -- An incorrectly formed string should cause a failure */
+	rc = of_property_read_string_array(np, "unterminated-string-list", strings, 4);
+	selftest(rc == -EILSEQ, "unterminated string array; rc=%i\n", rc);
+	/* -- parsing the correctly formed strings should still work: */
+	strings[2] = NULL;
+	rc = of_property_read_string_array(np, "unterminated-string-list", strings, 2);
+	selftest(rc == 2 && strings[2] == NULL, "of_property_read_string_array() failure; rc=%i\n", rc);
+	strings[1] = NULL;
+	rc = of_property_read_string_array(np, "phandle-list-names", strings, 1);
+	selftest(rc == 1 && strings[1] == NULL, "Overwrote end of string array; rc=%i, str='%s'\n", rc, strings[1]);
 }
 
 #define propcmp(p1, p2) (((p1)->length == (p2)->length) && \
@@ -881,7 +935,7 @@ static int __init of_selftest(void)
 	of_selftest_find_node_by_name();
 	of_selftest_dynamic();
 	of_selftest_parse_phandle_with_args();
-	of_selftest_property_match_string();
+	of_selftest_property_string();
 	of_selftest_property_copy();
 	of_selftest_changeset();
 	of_selftest_parse_interrupts();