You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
294 lines
8.6 KiB
294 lines
8.6 KiB
commit c02695d776406faaf63418e4e80c4a7023af0b4f
|
|
Author: H.J. Lu <hjl.tools@gmail.com>
|
|
Date: Wed Sep 16 16:00:14 2020 -0700
|
|
|
|
x86/CET: Update vfork to prevent child return
|
|
|
|
Child of vfork should either call _exit or one of the exec family of
|
|
functions. But normally there is nothing to prevent child of vfork from
|
|
return of the vfork-calling function. Simpilfy x86 vfork when shadow
|
|
stack is in use to introduce mismatched shadow stack in child of vfork
|
|
to trigger SIGSEGV when the child returns from the function in which
|
|
vfork was called.
|
|
---
|
|
|
|
diff --git a/sysdeps/unix/sysv/linux/i386/vfork.S b/sysdeps/unix/sysv/linux/i386/vfork.S
|
|
index ceb41db0bd..91277a639f 100644
|
|
--- a/sysdeps/unix/sysv/linux/i386/vfork.S
|
|
+++ b/sysdeps/unix/sysv/linux/i386/vfork.S
|
|
@@ -21,39 +21,6 @@
|
|
#include <bits/errno.h>
|
|
#include <tcb-offsets.h>
|
|
|
|
-#if SHSTK_ENABLED
|
|
-/* The shadow stack prevents us from pushing the saved return PC onto
|
|
- the stack and returning normally. Instead we pop the shadow stack
|
|
- and return directly. This is the safest way to return and ensures
|
|
- any stack manipulations done by the vfork'd child doesn't cause the
|
|
- parent to terminate when CET is enabled. */
|
|
-# undef SYSCALL_ERROR_HANDLER
|
|
-# ifdef PIC
|
|
-# define SYSCALL_ERROR_HANDLER \
|
|
-0: \
|
|
- calll .L1; \
|
|
-.L1: \
|
|
- popl %edx; \
|
|
-.L2: \
|
|
- addl $_GLOBAL_OFFSET_TABLE_ + (.L2 - .L1), %edx; \
|
|
- movl __libc_errno@gotntpoff(%edx), %edx; \
|
|
- negl %eax; \
|
|
- movl %eax, %gs:(%edx); \
|
|
- orl $-1, %eax; \
|
|
- jmp 1b;
|
|
-# else
|
|
-# define SYSCALL_ERROR_HANDLER \
|
|
-0: \
|
|
- movl __libc_errno@indntpoff, %edx; \
|
|
- negl %eax; \
|
|
- movl %eax, %gs:(%edx); \
|
|
- orl $-1, %eax; \
|
|
- jmp 1b;
|
|
-# endif
|
|
-# undef SYSCALL_ERROR_LABEL
|
|
-# define SYSCALL_ERROR_LABEL 0f
|
|
-#endif
|
|
-
|
|
/* Clone the calling process, but without copying the whole address space.
|
|
The calling process is suspended until the new process exits or is
|
|
replaced by a call to `execve'. Return -1 for errors, 0 to the new process,
|
|
@@ -70,20 +37,17 @@ ENTRY (__vfork)
|
|
movl $SYS_ify (vfork), %eax
|
|
int $0x80
|
|
|
|
-#if !SHSTK_ENABLED
|
|
/* Jump to the return PC. Don't jump directly since this
|
|
disturbs the branch target cache. Instead push the return
|
|
address back on the stack. */
|
|
pushl %ecx
|
|
cfi_adjust_cfa_offset (4)
|
|
-#endif
|
|
|
|
cmpl $-4095, %eax
|
|
/* Branch forward if it failed. */
|
|
jae SYSCALL_ERROR_LABEL
|
|
|
|
#if SHSTK_ENABLED
|
|
-1:
|
|
/* Check if shadow stack is in use. */
|
|
xorl %edx, %edx
|
|
rdsspd %edx
|
|
@@ -91,18 +55,19 @@ ENTRY (__vfork)
|
|
/* Normal return if shadow stack isn't in use. */
|
|
je L(no_shstk)
|
|
|
|
- /* Pop return address from shadow stack and jump back to caller
|
|
- directly. */
|
|
- movl $1, %edx
|
|
- incsspd %edx
|
|
+ testl %eax, %eax
|
|
+ /* In parent, normal return. */
|
|
+ jnz L(no_shstk)
|
|
+
|
|
+ /* NB: In child, jump back to caller via indirect branch without
|
|
+ popping shadow stack which is shared with parent. Keep shadow
|
|
+ stack mismatched so that child returns in the vfork-calling
|
|
+ function will trigger SIGSEGV. */
|
|
+ popl %ecx
|
|
+ cfi_adjust_cfa_offset (-4)
|
|
jmp *%ecx
|
|
|
|
L(no_shstk):
|
|
- /* Jump to the return PC. Don't jump directly since this
|
|
- disturbs the branch target cache. Instead push the return
|
|
- address back on the stack. */
|
|
- pushl %ecx
|
|
- cfi_adjust_cfa_offset (4)
|
|
#endif
|
|
|
|
ret
|
|
diff --git a/sysdeps/unix/sysv/linux/x86/Makefile b/sysdeps/unix/sysv/linux/x86/Makefile
|
|
index 50fd018fa3..6bfd6bec49 100644
|
|
--- a/sysdeps/unix/sysv/linux/x86/Makefile
|
|
+++ b/sysdeps/unix/sysv/linux/x86/Makefile
|
|
@@ -40,6 +40,11 @@ $(objpfx)tst-cet-property-2.out: $(objpfx)tst-cet-property-2 \
|
|
$(evaluate-test)
|
|
endif
|
|
|
|
+ifeq ($(subdir),posix)
|
|
+tests += tst-cet-vfork-1
|
|
+CFLAGS-tst-cet-vfork-1.c += -mshstk
|
|
+endif
|
|
+
|
|
ifeq ($(subdir),stdlib)
|
|
tests += tst-cet-setcontext-1
|
|
CFLAGS-tst-cet-setcontext-1.c += -mshstk
|
|
diff --git a/sysdeps/unix/sysv/linux/x86/tst-cet-vfork-1.c b/sysdeps/unix/sysv/linux/x86/tst-cet-vfork-1.c
|
|
new file mode 100644
|
|
index 0000000000..5b9fc8c170
|
|
--- /dev/null
|
|
+++ b/sysdeps/unix/sysv/linux/x86/tst-cet-vfork-1.c
|
|
@@ -0,0 +1,88 @@
|
|
+/* Verify that child of the vfork-calling function can't return when
|
|
+ shadow stack is in use.
|
|
+ Copyright (C) 2020 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
|
|
+ <https://www.gnu.org/licenses/>. */
|
|
+
|
|
+#include <stdio.h>
|
|
+#include <stdlib.h>
|
|
+#include <unistd.h>
|
|
+#include <errno.h>
|
|
+#include <sys/types.h>
|
|
+#include <sys/wait.h>
|
|
+#include <x86intrin.h>
|
|
+#include <support/test-driver.h>
|
|
+#include <support/xsignal.h>
|
|
+#include <support/xunistd.h>
|
|
+
|
|
+__attribute__ ((noclone, noinline))
|
|
+static void
|
|
+do_test_1 (void)
|
|
+{
|
|
+ pid_t p1;
|
|
+ int fd[2];
|
|
+
|
|
+ if (pipe (fd) == -1)
|
|
+ {
|
|
+ puts ("pipe failed");
|
|
+ _exit (EXIT_FAILURE);
|
|
+ }
|
|
+
|
|
+ if ((p1 = vfork ()) == 0)
|
|
+ {
|
|
+ pid_t p = getpid ();
|
|
+ TEMP_FAILURE_RETRY (write (fd[1], &p, sizeof (p)));
|
|
+ /* Child return should trigger SIGSEGV. */
|
|
+ return;
|
|
+ }
|
|
+ else if (p1 == -1)
|
|
+ {
|
|
+ puts ("vfork failed");
|
|
+ _exit (EXIT_FAILURE);
|
|
+ }
|
|
+
|
|
+ pid_t p2 = 0;
|
|
+ if (TEMP_FAILURE_RETRY (read (fd[0], &p2, sizeof (pid_t)))
|
|
+ != sizeof (pid_t))
|
|
+ puts ("pipd read failed");
|
|
+ else
|
|
+ {
|
|
+ int r;
|
|
+ if (TEMP_FAILURE_RETRY (waitpid (p1, &r, 0)) != p1)
|
|
+ puts ("waitpid failed");
|
|
+ else if (r != 0)
|
|
+ puts ("pip write in child failed");
|
|
+ }
|
|
+
|
|
+ /* Parent exits immediately so that parent returns without triggering
|
|
+ SIGSEGV when shadow stack isn't in use. */
|
|
+ _exit (EXIT_FAILURE);
|
|
+}
|
|
+
|
|
+static int
|
|
+do_test (void)
|
|
+{
|
|
+ /* NB: This test should trigger SIGSEGV with shadow stack enabled. */
|
|
+ if (_get_ssp () == 0)
|
|
+ return EXIT_UNSUPPORTED;
|
|
+ do_test_1 ();
|
|
+ /* Child exits immediately so that child returns without triggering
|
|
+ SIGSEGV when shadow stack isn't in use. */
|
|
+ _exit (EXIT_FAILURE);
|
|
+}
|
|
+
|
|
+#define EXPECTED_SIGNAL (_get_ssp () == 0 ? 0 : SIGSEGV)
|
|
+#include <support/test-driver.c>
|
|
diff --git a/sysdeps/unix/sysv/linux/x86_64/vfork.S b/sysdeps/unix/sysv/linux/x86_64/vfork.S
|
|
index 776d2fc610..613ff7e846 100644
|
|
--- a/sysdeps/unix/sysv/linux/x86_64/vfork.S
|
|
+++ b/sysdeps/unix/sysv/linux/x86_64/vfork.S
|
|
@@ -20,22 +20,6 @@
|
|
#include <bits/errno.h>
|
|
#include <tcb-offsets.h>
|
|
|
|
-#if SHSTK_ENABLED
|
|
-/* The shadow stack prevents us from pushing the saved return PC onto
|
|
- the stack and returning normally. Instead we pop the shadow stack
|
|
- and return directly. This is the safest way to return and ensures
|
|
- any stack manipulations done by the vfork'd child doesn't cause the
|
|
- parent to terminate when CET is enabled. */
|
|
-# undef SYSCALL_ERROR_HANDLER
|
|
-# define SYSCALL_ERROR_HANDLER \
|
|
-0: \
|
|
- SYSCALL_SET_ERRNO; \
|
|
- or $-1, %RAX_LP; \
|
|
- jmp 1b;
|
|
-# undef SYSCALL_ERROR_LABEL
|
|
-# define SYSCALL_ERROR_LABEL 0f
|
|
-#endif
|
|
-
|
|
/* Clone the calling process, but without copying the whole address space.
|
|
The calling process is suspended until the new process exits or is
|
|
replaced by a call to `execve'. Return -1 for errors, 0 to the new process,
|
|
@@ -53,17 +37,14 @@ ENTRY (__vfork)
|
|
movl $SYS_ify (vfork), %eax
|
|
syscall
|
|
|
|
-#if !SHSTK_ENABLED
|
|
/* Push back the return PC. */
|
|
pushq %rdi
|
|
cfi_adjust_cfa_offset(8)
|
|
-#endif
|
|
|
|
cmpl $-4095, %eax
|
|
jae SYSCALL_ERROR_LABEL /* Branch forward if it failed. */
|
|
|
|
#if SHSTK_ENABLED
|
|
-1:
|
|
/* Check if shadow stack is in use. */
|
|
xorl %esi, %esi
|
|
rdsspq %rsi
|
|
@@ -71,16 +52,19 @@ ENTRY (__vfork)
|
|
/* Normal return if shadow stack isn't in use. */
|
|
je L(no_shstk)
|
|
|
|
- /* Pop return address from shadow stack and jump back to caller
|
|
- directly. */
|
|
- movl $1, %esi
|
|
- incsspq %rsi
|
|
+ testl %eax, %eax
|
|
+ /* In parent, normal return. */
|
|
+ jnz L(no_shstk)
|
|
+
|
|
+ /* NB: In child, jump back to caller via indirect branch without
|
|
+ popping shadow stack which is shared with parent. Keep shadow
|
|
+ stack mismatched so that child returns in the vfork-calling
|
|
+ function will trigger SIGSEGV. */
|
|
+ popq %rdi
|
|
+ cfi_adjust_cfa_offset(-8)
|
|
jmp *%rdi
|
|
|
|
L(no_shstk):
|
|
- /* Push back the return PC. */
|
|
- pushq %rdi
|
|
- cfi_adjust_cfa_offset(8)
|
|
#endif
|
|
|
|
/* Normal return. */
|
|
--
|
|
2.26.2
|
|
|