Date: Wed, 2 May 2018 08:27:00 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r333168 - stable/11/lib/libc/secure Message-ID: <201805020827.w428R0Bg095370@repo.freebsd.org>
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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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