From: "LeMay, Michael" <michael.lemay@intel.com>
To: "musl@lists.openwall.com" <musl@lists.openwall.com>
Subject: [RFC PATCH 2/7] avoid invoking the vDSO when SafeStack is enabled
Date: Tue, 27 Sep 2016 15:35:17 -0700 [thread overview]
Message-ID: <87d625c3-577d-0581-ce82-ca0f8b7b6154@intel.com> (raw)
The Linux vDSO code may be incompatible with programs that enable
segmentation-hardened SafeStack. This patch prevents the vDSO from
being invoked when segmentation-hardened SafeStack is enabled.
Signed-off-by: Michael LeMay <michael.lemay@intel.com>
---
arch/i386/syscall_arch.h | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/arch/i386/syscall_arch.h b/arch/i386/syscall_arch.h
index 4c9d874..08e0910 100644
--- a/arch/i386/syscall_arch.h
+++ b/arch/i386/syscall_arch.h
@@ -52,8 +52,21 @@ static inline long __syscall6(long n, long a1, long
a2, long a3, long a4, long a
return __ret;
}
+#if !SAFE_STACK
+/* The vDSO is not compiled with segmentation-hardened SafeStack. Avoid
+ * invoking the vDSO when hardened SafeStack is enabled, since it may
try to
+ * access the stack using memory operands with base registers other
than EBP or
+ * ESP without also using a stack segment override prefix. A special
compiler
+ * pass needs to be used to add such prefixes, and it is unlikely that
a pass
+ * of that sort was applied when the vDSO was compiled.
+ *
+ * A possible alternative to disabling the use of the vDSO may be to
load the
+ * default flat data segment into DS prior to invoking the vDSO and
reloading
+ * the restricted data segment into DS after the vDSO routine returns.
+ */
#define VDSO_USEFUL
#define VDSO_CGT_SYM "__vdso_clock_gettime"
#define VDSO_CGT_VER "LINUX_2.6"
+#endif
#define SYSCALL_USE_SOCKETCALL
--
2.7.4
next reply other threads:[~2016-09-27 22:35 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-27 22:35 LeMay, Michael [this message]
2016-09-27 22:46 LeMay, Michael
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