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154 lines
4.1 KiB
C
154 lines
4.1 KiB
C
/* Stack executability handling for GNU dynamic linker. Linux version.
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Copyright (C) 2003, 2004, 2005, 2006 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 <ldsodefs.h>
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#include <sys/mman.h>
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#include <errno.h>
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#include <libintl.h>
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#include <stdbool.h>
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#include <stackinfo.h>
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#include <caller.h>
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#include <sysdep.h>
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#include <kernel-features.h>
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extern int __stack_prot attribute_relro attribute_hidden;
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int
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internal_function
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_dl_make_stack_executable (void **stack_endp)
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{
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/* This gives us the highest/lowest page that needs to be changed. */
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uintptr_t page = ((uintptr_t) *stack_endp
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& -(intptr_t) GLRO(dl_pagesize));
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int result = 0;
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/* Challenge the caller. */
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if (__builtin_expect (__check_caller (RETURN_ADDRESS (0),
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allow_ldso|allow_libpthread) != 0, 0)
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|| __builtin_expect (*stack_endp != __libc_stack_end, 0))
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return EPERM;
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/* Newer Linux kernels support a flag to make our job easy. */
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#if defined PROT_GROWSDOWN || defined PROT_GROWSUP
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# if __ASSUME_PROT_GROWSUPDOWN == 0
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static bool no_growsupdown;
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if (! no_growsupdown)
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# endif
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{
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if (__builtin_expect (__mprotect ((void *) page, GLRO(dl_pagesize),
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__stack_prot) == 0, 1))
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goto return_success;
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# if __ASSUME_PROT_GROWSUPDOWN == 0
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if (errno == EINVAL)
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no_growsupdown = true;
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else
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# endif
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{
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result = errno;
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goto out;
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}
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}
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#endif
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/* There is always a hole in the address space below the bottom of the
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stack. So when we make an mprotect call that starts below the bottom
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of the stack, it will include the hole and fail with ENOMEM.
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We start with a random guess at how deep the stack might have gotten
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so as to have extended the GROWSDOWN mapping to lower pages. */
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#if __ASSUME_PROT_GROWSUPDOWN == 0
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size_t size = GLRO(dl_pagesize) * 8;
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# if _STACK_GROWS_DOWN
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page = page + GLRO(dl_pagesize) - size;
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while (1)
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{
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if (__mprotect ((void *) page, size,
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__stack_prot & ~PROT_GROWSDOWN) == 0)
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/* We got this chunk changed; loop to do another chunk below. */
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page -= size;
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else
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{
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if (errno != ENOMEM) /* Unexpected failure mode. */
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{
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result = errno;
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goto out;
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}
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if (size == GLRO(dl_pagesize))
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/* We just tried to mprotect the top hole page and failed.
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We are done. */
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break;
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/* Our mprotect call failed because it started below the lowest
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stack page. Try again on just the top half of that region. */
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size /= 2;
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page += size;
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}
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}
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# elif _STACK_GROWS_UP
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while (1)
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{
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if (__mprotect ((void *) page, size, __stack_prot & ~PROT_GROWSUP) == 0)
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/* We got this chunk changed; loop to do another chunk below. */
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page += size;
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else
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{
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if (errno != ENOMEM) /* Unexpected failure mode. */
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{
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result = errno;
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goto out;
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}
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if (size == GLRO(dl_pagesize))
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/* We just tried to mprotect the lowest hole page and failed.
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We are done. */
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break;
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/* Our mprotect call failed because it extended past the highest
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stack page. Try again on just the bottom half of that region. */
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size /= 2;
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}
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}
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# else
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# error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP"
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# endif
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#endif
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return_success:
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/* Clear the address. */
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*stack_endp = NULL;
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/* Remember that we changed the permission. */
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GL(dl_stack_flags) |= PF_X;
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out:
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#ifdef check_consistency
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check_consistency ();
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#endif
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return result;
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}
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rtld_hidden_def (_dl_make_stack_executable)
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