Author: kib
Date: Wed May 2 08:26:59 2018
New Revision: 333168
URL: https://svnweb.freebsd.org/changeset/base/333168
Log:
MFC r332940:
Carefully update stack guard bytes inside __guard_setup().
Modified:
stable/11/lib/libc/secure/stack_protector.c
Directory Properties:
stable/11/ (props changed)
Modified: stable/11/lib/libc/secure/stack_protector.c
==============================================================================
--- stable/11/lib/libc/secure/stack_protector.c Wed May 2 08:24:59 2018
(r333167)
+++ stable/11/lib/libc/secure/stack_protector.c Wed May 2 08:26:59 2018
(r333168)
@@ -54,15 +54,27 @@ static void
__guard_setup(void)
{
static const int mib[2] = { CTL_KERN, KERN_ARND };
+ volatile long tmp_stack_chk_guard[nitems(__stack_chk_guard)];
size_t len;
- int error;
+ int error, idx;
if (__stack_chk_guard[0] != 0)
return;
- error = _elf_aux_info(AT_CANARY, __stack_chk_guard,
- sizeof(__stack_chk_guard));
- if (error == 0 && __stack_chk_guard[0] != 0)
+ /*
+ * Avoid using functions which might have stack protection
+ * enabled, to update the __stack_chk_guard. First fetch the
+ * data into a temporal array, then do manual volatile copy to
+ * not allow optimizer to call memcpy() behind us.
+ */
+ error = _elf_aux_info(AT_CANARY, (void *)tmp_stack_chk_guard,
+ sizeof(tmp_stack_chk_guard));
+ if (error == 0 && tmp_stack_chk_guard[0] != 0) {
+ for (idx = 0; idx < nitems(__stack_chk_guard); idx++) {
+ __stack_chk_guard[idx] = tmp_stack_chk_guard[idx];
+ tmp_stack_chk_guard[idx] = 0;
+ }
return;
+ }
len = sizeof(__stack_chk_guard);
if (__sysctl(mib, nitems(mib), __stack_chk_guard, &len, NULL, 0) ==
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