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f33632ccd1
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 with a
space to store shadow stack pointer. It 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 its 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/jmp_buf-ssp.sym: 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 (gen-as-const-headers):
Add jmp_buf-ssp.sym.
(tests): Add tst-saved_mask-1.
56 lines
1.8 KiB
C
56 lines
1.8 KiB
C
/* Test that sigprocmask does not read from the unused part of jmpbuf.
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Copyright (C) 2017 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <stdlib.h>
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#include <signal.h>
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#include <string.h>
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#include <errno.h>
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#include <setjmpP.h>
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#include <support/next_to_fault.h>
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#define SIZEOF_SIGSET_T sizeof (__jmp_buf_sigset_t)
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static int
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do_test (void)
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{
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sigjmp_buf sj;
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struct support_next_to_fault sigset_t_buf
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= support_next_to_fault_allocate (SIZEOF_SIGSET_T);
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sigset_t *m_p = (sigset_t *) sigset_t_buf.buffer;
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sigset_t m;
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sigemptyset (&m);
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memcpy (m_p, &m, SIZEOF_SIGSET_T);
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sigprocmask (SIG_SETMASK, m_p, NULL);
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memcpy (&m, m_p, SIZEOF_SIGSET_T);
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if (sigsetjmp (sj, 0) == 0)
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{
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sigaddset (&m, SIGUSR1);
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memcpy (m_p, &m, SIZEOF_SIGSET_T);
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sigprocmask (SIG_SETMASK, m_p, NULL);
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memcpy (&m, m_p, SIZEOF_SIGSET_T);
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siglongjmp (sj, 1);
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return EXIT_FAILURE;
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}
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sigprocmask (SIG_SETMASK, NULL, m_p);
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memcpy (&m, m_p, SIZEOF_SIGSET_T);
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return sigismember (&m, SIGUSR1) ? EXIT_SUCCESS : EXIT_FAILURE;
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}
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#include <support/test-driver.c>
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