From: Nick Alcock <nick.alcock@oracle.com>
Date: Mon, 26 Dec 2016 09:09:06 +0000 (+0100)
Subject: Do not stack-protect sigreturn stubs [BZ #7065]
X-Git-Tag: glibc-2.25~148
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2e6c45c59bcd40f1ae8466cbd32f4d263ff45619;p=thirdparty%2Fglibc.git

Do not stack-protect sigreturn stubs [BZ #7065]

These are called from the kernel with the stack at a carefully-
chosen location so that the stack frame can be restored: they must not
move the stack pointer lest garbage be restored into the registers.

We explicitly inhibit protection for SPARC and for signal/sigreturn.c:
other arches either define their sigreturn stubs in .S files, or (i386,
x86_64, mips) use macros expanding to top-level asm blocks and explicit
labels in the text section to mock up a "function" without telling the
compiler that one is there at all.
---

diff --git a/ChangeLog b/ChangeLog
index 99749a5b757..edf85237ac5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2016-12-26  Nick Alcock  <nick.alcock@oracle.com>
+
+	[BZ #7065]
+	* signal/Makefile (CFLAGS-sigreturn.c): Use $(no-stack-protector).
+	* sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c:
+	(__rt_sigreturn_stub): Use inhibit_stack_protector.
+	* sysdeps/unix/sysv/linux/sparc/sparc32/sigaction.c
+	(__rt_sigreturn_stub, __sigreturn_stub): Likewise.
+
 2016-12-26  Nick Alcock  <nick.alcock@oracle.com>
 
 	[BZ #7065]
diff --git a/signal/Makefile b/signal/Makefile
index 9d29ff49f32..ccd6f516194 100644
--- a/signal/Makefile
+++ b/signal/Makefile
@@ -48,3 +48,5 @@ CFLAGS-sigsuspend.c = -fexceptions -fasynchronous-unwind-tables
 CFLAGS-sigtimedwait.c = -fexceptions -fasynchronous-unwind-tables
 CFLAGS-sigwait.c = -fexceptions -fasynchronous-unwind-tables
 CFLAGS-sigwaitinfo.c = -fexceptions -fasynchronous-unwind-tables
+
+CFLAGS-sigreturn.c = $(no-stack-protector)
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/sigaction.c b/sysdeps/unix/sysv/linux/sparc/sparc32/sigaction.c
index 5aa3c3516e9..b75142fc6b6 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/sigaction.c
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/sigaction.c
@@ -65,7 +65,9 @@ libc_hidden_def (__libc_sigaction)
 #include <nptl/sigaction.c>
 
 
-static void
+static
+inhibit_stack_protector
+void
 __rt_sigreturn_stub (void)
 {
   __asm__ ("mov %0, %%g1\n\t"
@@ -74,7 +76,9 @@ __rt_sigreturn_stub (void)
 	   : "i" (__NR_rt_sigreturn));
 }
 
-static void
+static
+inhibit_stack_protector
+void
 __sigreturn_stub (void)
 {
   __asm__ ("mov %0, %%g1\n\t"
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c b/sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c
index 50c444c72d1..058c0114492 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/sigaction.c
@@ -66,7 +66,9 @@ libc_hidden_def (__libc_sigaction)
 #include <nptl/sigaction.c>
 
 
-static void
+static
+inhibit_stack_protector
+void
 __rt_sigreturn_stub (void)
 {
   __asm__ ("mov %0, %%g1\n\t"