| Message ID | 20180404004211.6141-3-ahs3@redhat.com (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Headers | show |
diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c index b6ac8162a2c0..672a1f22c3a5 100644 --- a/drivers/acpi/tables.c +++ b/drivers/acpi/tables.c @@ -271,8 +271,7 @@ acpi_parse_entries_array(char *id, unsigned long table_size, entry = (struct acpi_subtable_header *) ((unsigned long)table_header + table_size); - while (((unsigned long)entry) + sizeof(struct acpi_subtable_header) < - table_end) { + while (((unsigned long)entry + entry->length) <= table_end) { if (max_entries && count >= max_entries) break;
For ACPI tables that have subtables, acpi_parse_entries_array() gets used to step through each of the subtables in memory. The primary loop for this was checking that the beginning location of the subtable being examined plus the length of struct acpi_subtable_header was not beyond the end of the complete ACPI table; if it wasn't, the subtable could be examined, but if it was the loop would terminate as it should. In the middle of this subtable loop, a callback is used to examine the subtable in detail. Should the callback function try to examine elements of the subtable that are located past the subtable header, and the ACPI table containing this subtable has an incorrect length, it is possible to access either invalid or protected memory and cause a fault. And, the length of struct acpi_subtable_header will always be smaller than the length of the actual subtable. To fix this, we make the main loop check that the beginning of the subtable being examined plus the actual length of the subtable does not go past the end of the enclosing ACPI table. While this cannot protect us from malicious callback functions, it can prevent us from failing because of some poorly constructed ACPI tables. Found by inspection. There is no functional change to existing code that is known to work when calling acpi_parse_entries_array(). Signed-off-by: Al Stone <ahs3@redhat.com> Cc: Rafael J. Wysocki <rjw@rjwysocki.net> Cc: Len Brown <lenb@kernel.org> --- drivers/acpi/tables.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)