Patchwork [2/2] jmpbuf: Add paddings for target specific usage

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Submitter H.J. Lu
Date Nov. 25, 2017, 4:34 p.m.
Message ID <CAMe9rOr3bKzEE-0ab7Yue_rS0snMZ3_8b=BWfJzjkjvgAp39XQ@mail.gmail.com>
Download mbox | patch
Permalink /patch/24527/
State New
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Comments

H.J. Lu - Nov. 25, 2017, 4:34 p.m.
On Tue, Nov 21, 2017 at 2:22 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Wed, Nov 15, 2017 at 5:20 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Wed, Nov 15, 2017 at 3:10 AM, Florian Weimer <fweimer@redhat.com> wrote:
>>> On 11/14/2017 02:10 PM, H.J. Lu wrote:
>>>>
>>>> +static int
>>>> +do_test (void)
>>>> +{
>>>> +  sigjmp_buf sj;
>>>> +  struct support_next_to_fault sigset_t_buf
>>>> +    = support_next_to_fault_allocate (SIZEOF_SIGSET_T);
>>>> +  sigset_t *m_p = (sigset_t *) sigset_t_buf.buffer;
>>>> +  sigset_t m;
>>>> +
>>>> +  sigemptyset (&m);
>>>> +  memcpy (m_p, &m, SIZEOF_SIGSET_T);
>>>> +  sigprocmask (SIG_SETMASK, m_p, NULL);
>>>> +  memcpy (&m, m_p, SIZEOF_SIGSET_T);
>>>> +  if (sigsetjmp (sj, 0) == 0)
>>>> +    {
>>>> +      sigaddset (&m, SIGUSR1);
>>>> +      memcpy (m_p, &m, SIZEOF_SIGSET_T);
>>>> +      sigprocmask (SIG_SETMASK, m_p, NULL);
>>>> +      memcpy (&m, m_p, SIZEOF_SIGSET_T);
>>>> +      siglongjmp (sj, 1);
>>>> +      return EXIT_FAILURE;
>>>> +    }
>>>> +  sigprocmask (SIG_SETMASK, NULL, m_p);
>>>> +  memcpy (&m, m_p, SIZEOF_SIGSET_T);
>>>> +  return sigismember (&m, SIGUSR1) ? EXIT_SUCCESS : EXIT_FAILURE;
>>>> +}
>>>
>>>
>>> Sorry, I don't understand anymore what this test is supposed to test and
>>> how.
>>
>> This tests the reduced __jmp_buf_sigset_t used by __saved_mask is
>> bigger than sigset expected by kernel.
>>
>>> To be honest, I don't like how you inject the internal definition of
>>> jmp_buf.  Is this the way we do it for the nptl types?
>>
>> I only need to make some room in
>>
>> /* Calling environment, plus possibly a saved signal mask.  */
>> struct __jmp_buf_tag
>>   {
>>     /* NOTE: The machine-dependent definitions of `__sigsetjmp'
>>        assume that a `jmp_buf' begins with a `__jmp_buf' and that
>>        `__mask_was_saved' follows it.  Do not move these members
>>        or add others before it.  */
>>     __jmp_buf __jmpbuf; /* Calling environment.  */
>>     int __mask_was_saved; /* Saved the signal mask?  */
>>     __sigset_t __saved_mask; /* Saved signal mask.  */
>>   };
>>
>> for target specific purpose.   I changed it to
>>
>> struct __jmp_buf_tag
>>   {
>>     /* NOTE: The machine-dependent definitions of `__sigsetjmp'
>>        assume that a `jmp_buf' begins with a `__jmp_buf' and that
>>        `__mask_was_saved' follows it.  Do not move these members
>>        or add others before it.  */
>>     __jmp_buf __jmpbuf; /* Calling environment.  */
>>     int __mask_was_saved; /* Saved the signal mask?  */
>>     union
>>     {
>>     __sigset_t __saved_mask_compat;
>>     struct
>>       {
>> __jmp_buf_sigset_t __saved_mask;
>> /* Paddings for architecture specific usage.  */
>> unsigned long int __padding[12];
>>       } __saved;
>>     }  __saved_mask;
>>   };
>>
>> #define __saved_mask __saved_mask.__saved.__saved_mask
>>
>> I did only to  __sigset_t  in __jmp_buf_tag and this test verifies that the size
>> of __jmp_buf_sigset_t works with sigprocmask.
>>
>> Are you suggesting we make some room in __sigset_t directly?  This will
>> require very extensive changes. If not, what do you exactly suggest?
>>
>>> I think you should check _JUMP_BUF_SIGSET_NSIG against a kernel constant
>>> (_NSIGS?) somewhere.
>>
>> There is a _Static_assert in include/setjmp.h.  But it isn't triggered.  This
>> updated patch moves it to sysdeps/unix/sysv/linux/__saved_mask.h.   Now
>> I got
>>
>> ../sysdeps/unix/sysv/linux/__saved_mask.h:32:1: error: static
>> assertion failed: "size of ___saved_mask < size of
>> __sigprocmask_sigset_t"
>>  _Static_assert (sizeof (___saved_mask) >= sizeof (__sigprocmask_sigset_t),
>>
>> if __jmp_buf_sigset_t is too small.
>>
>> --
>> H.J.
>
> Any comments, suggestions or objections?  The patch is at
>
> https://sourceware.org/ml/libc-alpha/2017-11/msg00510.html
>

This is the updated patch.  It limited the changes to Linux/x86.
Any comments?

Patch

From 71ac6d741e74e8be54fdc74132bce3def8d90bea Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Sat, 10 Jun 2017 17:23:06 -0700
Subject: [PATCH] x86: Add paddings in jmpbuf for shadow stack pointer

To support Shadow Stack (SHSTK) in Intel Control-flow Enforcement
Technology (CET) in setjmp/longjmp, we need to save shadow stack
pointer in jmp_buf.  The __saved_mask field in jmp_buf has type
of __sigset_t.  On Linux, __sigset_t is defined as

 #define _SIGSET_NWORDS (1024 / (8 * sizeof (unsigned long int)))
typedef struct
{
  unsigned long int __val[_SIGSET_NWORDS];
} __sigset_t;

which is much bigger than expected by the __sigprocmask system call,
which has

typedef struct {
        unsigned long sig[_NSIG_WORDS];
} sigset_t;

For Linux/x86, we can shrink __sigset_t used by __saved_mask in jmp_buf
to add paddings for shadow stack pointer.  As long as the new __sigset_t
is not smaller than sigset_t expected by the __sigprocmask system call,
it should work correctly.  This patch adds an internal header file,
<setjmpP.h>, to define __jmp_buf_sigset_t for __saved_mask in jmp_buf
for Linux/x86 and verifies __jmp_buf_sigset_t has the suitable size for
the __sigprocmask system call.   A run-time test, tst-saved_mask-1.c, is
added to verify that size of __jmp_buf_sigset_t is sufficient.  If size
is too small, the test fails with

rt_sigprocmask(SIG_SETMASK, strace: umoven: short read (4 < 8) @0x7fa8aa28effc
0x7fa8aa28effc, NULL, 8) = -1 EFAULT (Bad address)
rt_sigprocmask(SIG_SETMASK, strace: umoven: short read (4 < 8) @0x7fa8aa28effc
0x7fa8aa28effc, NULL, 8) = -1 EFAULT (Bad address)
rt_sigprocmask(SIG_SETMASK, NULL, 0x7fa8aa28effc, 8) = -1 EFAULT (Bad address)
exit_group(1)                           = ?

Tested with build-many-glibcs.py.

	* debug/longjmp_chk.c: Include <setjmpP.h> instead of
	<setjmp.h>.
	* setjmp/longjmp.c: Include <setjmpP.h> instead of <setjmp.h>.
	(__libc_siglongjmp): Cast &env[0].__saved_mask to "sigset_t *".
	* setjmp/sigjmp.c: Include <setjmpP.h> instead of <setjmp.h>.
	(__sigjmp_save): Cast &env[0].__saved_mask to "sigset_t *".
	* sysdeps/generic/setjmpP.h: New file.
	* sysdeps/unix/sysv/linux/x86/__jmpbuf_arch_t.h: Likewise.
	* sysdeps/unix/sysv/linux/x86/__saved_mask.h: Likewise.
	* sysdeps/unix/sysv/linux/x86/setjmpP.h: Likewise.
	* sysdeps/unix/sysv/linux/x86/tst-saved_mask-1.c: Likewise.
	* sysdeps/unix/sysv/linux/x86/Makefile (tests): Add
	tst-saved_mask-1.
---
 debug/longjmp_chk.c                            |  2 +-
 setjmp/longjmp.c                               |  5 ++-
 setjmp/sigjmp.c                                |  4 +-
 sysdeps/generic/setjmpP.h                      | 24 +++++++++++
 sysdeps/unix/sysv/linux/x86/Makefile           |  4 ++
 sysdeps/unix/sysv/linux/x86/__jmpbuf_arch_t.h  | 43 ++++++++++++++++++++
 sysdeps/unix/sysv/linux/x86/__saved_mask.h     | 34 ++++++++++++++++
 sysdeps/unix/sysv/linux/x86/setjmpP.h          | 28 +++++++++++++
 sysdeps/unix/sysv/linux/x86/tst-saved_mask-1.c | 56 ++++++++++++++++++++++++++
 9 files changed, 195 insertions(+), 5 deletions(-)
 create mode 100644 sysdeps/generic/setjmpP.h
 create mode 100644 sysdeps/unix/sysv/linux/x86/__jmpbuf_arch_t.h
 create mode 100644 sysdeps/unix/sysv/linux/x86/__saved_mask.h
 create mode 100644 sysdeps/unix/sysv/linux/x86/setjmpP.h
 create mode 100644 sysdeps/unix/sysv/linux/x86/tst-saved_mask-1.c

diff --git a/debug/longjmp_chk.c b/debug/longjmp_chk.c
index 1cea6c05ef..61be0da0cd 100644
--- a/debug/longjmp_chk.c
+++ b/debug/longjmp_chk.c
@@ -15,7 +15,7 @@ 
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
-#include <setjmp.h>
+#include <setjmpP.h>
 
 #define __longjmp ____longjmp_chk
 #define __libc_siglongjmp __longjmp_chk
diff --git a/setjmp/longjmp.c b/setjmp/longjmp.c
index 2453c2c124..e144a874d7 100644
--- a/setjmp/longjmp.c
+++ b/setjmp/longjmp.c
@@ -16,7 +16,7 @@ 
    <http://www.gnu.org/licenses/>.  */
 
 #include <stddef.h>
-#include <setjmp.h>
+#include <setjmpP.h>
 #include <signal.h>
 
 
@@ -31,7 +31,8 @@  __libc_siglongjmp (sigjmp_buf env, int val)
 
   if (env[0].__mask_was_saved)
     /* Restore the saved signal mask.  */
-    (void) __sigprocmask (SIG_SETMASK, &env[0].__saved_mask,
+    (void) __sigprocmask (SIG_SETMASK,
+			  (sigset_t *) &env[0].__saved_mask,
 			  (sigset_t *) NULL);
 
   /* Call the machine-dependent function to restore machine state.  */
diff --git a/setjmp/sigjmp.c b/setjmp/sigjmp.c
index 30839ae819..32b727fae8 100644
--- a/setjmp/sigjmp.c
+++ b/setjmp/sigjmp.c
@@ -16,7 +16,7 @@ 
    <http://www.gnu.org/licenses/>.  */
 
 #include <stddef.h>
-#include <setjmp.h>
+#include <setjmpP.h>
 #include <signal.h>
 
 /* This function is called by the `sigsetjmp' macro
@@ -28,7 +28,7 @@  __sigjmp_save (sigjmp_buf env, int savemask)
 {
   env[0].__mask_was_saved = (savemask &&
 			     __sigprocmask (SIG_BLOCK, (sigset_t *) NULL,
-					    &env[0].__saved_mask) == 0);
+					    (sigset_t *) &env[0].__saved_mask) == 0);
 
   return 0;
 }
diff --git a/sysdeps/generic/setjmpP.h b/sysdeps/generic/setjmpP.h
new file mode 100644
index 0000000000..a878ce6b35
--- /dev/null
+++ b/sysdeps/generic/setjmpP.h
@@ -0,0 +1,24 @@ 
+/* Internal header file for <setjmp.h>.  Generic version.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef	_SETJMPP_H
+#define	_SETJMPP_H	1
+
+#include <setjmp.h>
+
+#endif /* setjmpP.h  */
diff --git a/sysdeps/unix/sysv/linux/x86/Makefile b/sysdeps/unix/sysv/linux/x86/Makefile
index c069570683..111ff9ff58 100644
--- a/sysdeps/unix/sysv/linux/x86/Makefile
+++ b/sysdeps/unix/sysv/linux/x86/Makefile
@@ -19,3 +19,7 @@  endif
 ifeq ($(subdir),elf)
 sysdep_routines += dl-vdso
 endif
+
+ifeq ($(subdir),setjmp)
+tests += tst-saved_mask-1
+endif
diff --git a/sysdeps/unix/sysv/linux/x86/__jmpbuf_arch_t.h b/sysdeps/unix/sysv/linux/x86/__jmpbuf_arch_t.h
new file mode 100644
index 0000000000..a170f3ef9b
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86/__jmpbuf_arch_t.h
@@ -0,0 +1,43 @@ 
+/* __jmpbuf_arch_t defition for Linux/x86.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <bits/types/__sigset_t.h>
+
+/* The biggest signal number + 1.  As of kernel 4.13, the maximum number
+   of signals is 128 on MIPS.  Define it to 257 to leave some rooms for
+   the future.  */
+#define _JUMP_BUF_SIGSET_NSIG	257
+/* Number of longs to hold all signals.  */
+#define _JUMP_BUF_SIGSET_NWORDS \
+  ((_JUMP_BUF_SIGSET_NSIG - 1 + 7) / (8 * sizeof (unsigned long int)))
+
+typedef struct
+  {
+    unsigned long int __val[_JUMP_BUF_SIGSET_NWORDS];
+  } __jmp_buf_sigset_t;
+
+typedef union
+  {
+    __sigset_t __saved_mask_compat;
+    struct
+      {
+	__jmp_buf_sigset_t __saved_mask;
+	/* Paddings for architecture specific usage.  */
+	unsigned long int __padding[12];
+      } __saved;
+  } __jmpbuf_arch_t;
diff --git a/sysdeps/unix/sysv/linux/x86/__saved_mask.h b/sysdeps/unix/sysv/linux/x86/__saved_mask.h
new file mode 100644
index 0000000000..98b3bbc836
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86/__saved_mask.h
@@ -0,0 +1,34 @@ 
+/* __saved_mask defition for Linux/x86.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* Saved signal mask.  */
+#define __saved_mask __saved_mask.__saved.__saved_mask
+
+#include <signal.h>
+
+#define _SIGPROCMASK_NSIG_WORDS (_NSIG / (8 * sizeof (unsigned long int)))
+
+typedef struct
+  {
+    unsigned long int __val[_SIGPROCMASK_NSIG_WORDS];
+  } __sigprocmask_sigset_t;
+
+extern jmp_buf ___buf;
+extern  __typeof (___buf[0].__saved_mask) ___saved_mask;
+_Static_assert (sizeof (___saved_mask) >= sizeof (__sigprocmask_sigset_t),
+		"size of ___saved_mask < size of __sigprocmask_sigset_t");
diff --git a/sysdeps/unix/sysv/linux/x86/setjmpP.h b/sysdeps/unix/sysv/linux/x86/setjmpP.h
new file mode 100644
index 0000000000..03bc477166
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86/setjmpP.h
@@ -0,0 +1,28 @@ 
+/* Internal header file for <setjmp.h>.  Linux/x86 version.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef	_SETJMPP_H
+#define	_SETJMPP_H	1
+
+#include <__jmpbuf_arch_t.h>
+#undef __sigset_t
+#define __sigset_t __jmpbuf_arch_t
+#include <setjmp.h>
+#include <__saved_mask.h>
+
+#endif /* setjmpP.h  */
diff --git a/sysdeps/unix/sysv/linux/x86/tst-saved_mask-1.c b/sysdeps/unix/sysv/linux/x86/tst-saved_mask-1.c
new file mode 100644
index 0000000000..1c5adebf0b
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86/tst-saved_mask-1.c
@@ -0,0 +1,56 @@ 
+/* Test that sigprocmask does not read from the unused part of jmpbuf.
+   Copyright (C) 2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <stdlib.h>
+#include <signal.h>
+#include <setjmp.h>
+#include <string.h>
+#include <errno.h>
+#include <__jmpbuf_arch_t.h>
+#include <support/next_to_fault.h>
+
+#define SIZEOF_SIGSET_T sizeof (__jmp_buf_sigset_t)
+
+static int
+do_test (void)
+{
+  sigjmp_buf sj;
+  struct support_next_to_fault sigset_t_buf
+    = support_next_to_fault_allocate (SIZEOF_SIGSET_T);
+  sigset_t *m_p = (sigset_t *) sigset_t_buf.buffer;
+  sigset_t m;
+
+  sigemptyset (&m);
+  memcpy (m_p, &m, SIZEOF_SIGSET_T);
+  sigprocmask (SIG_SETMASK, m_p, NULL);
+  memcpy (&m, m_p, SIZEOF_SIGSET_T);
+  if (sigsetjmp (sj, 0) == 0)
+    {
+      sigaddset (&m, SIGUSR1);
+      memcpy (m_p, &m, SIZEOF_SIGSET_T);
+      sigprocmask (SIG_SETMASK, m_p, NULL);
+      memcpy (&m, m_p, SIZEOF_SIGSET_T);
+      siglongjmp (sj, 1);
+      return EXIT_FAILURE;
+    }
+  sigprocmask (SIG_SETMASK, NULL, m_p);
+  memcpy (&m, m_p, SIZEOF_SIGSET_T);
+  return sigismember (&m, SIGUSR1) ? EXIT_SUCCESS : EXIT_FAILURE;
+}
+
+#include <support/test-driver.c>
-- 
2.14.3