ecdeaac05f
* sysdeps/generic/ldsodefs.h (struct rtld_global): Add _dl_stack_flags and _dl_make_stack_executable_hook. Declare _dl_make_stack_executable. * elf/rtld.c (_rtld_global): Add initializer for _dl_stack_flags. (dl_main): Reset _dl_stack_flags according to PT_GNU_STACK phdr. Initialize _dl_make_stack_executable_hook. * elf/dl-support.c: Define those new variables. (_dl_non_dynamic_init): Scan phdrs for PT_GNU_STACK. (_dl_phdr): Fix type. * elf/dl-load.c (_dl_map_object_from_fd): Grok PT_GNU_STACK phdr and enable execute permission for the stack if necessary. * sysdeps/generic/dl-execstack.c: New file. * elf/Makefile (dl-routines): Add it. * elf/Versions (ld: GLIBC_PRIVATE): Add _dl_make_stack_executable. * sysdeps/unix/sysv/linux/dl-execstack.c: New file.
116 lines
3.7 KiB
C
116 lines
3.7 KiB
C
/* Stack executability handling for GNU dynamic linker. Linux version.
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Copyright (C) 2003 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, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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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 <stdbool.h>
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#include <stackinfo.h>
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extern void *__libc_stack_end;
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int
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internal_function
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_dl_make_stack_executable (void)
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{
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if (__libc_stack_end == 0)
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/* XXX for a DT_NEEDED library that requires the change,
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this is not initialized yet!
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*/
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return ENOSYS;
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#if _STACK_GROWS_DOWN
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/* This gives us the highest page that needs to be changed. */
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uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize);
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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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size_t size = GL(dl_pagesize) * 8;
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page = page + GL(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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PROT_READ|PROT_WRITE|PROT_EXEC) == 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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return errno;
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if (size == GL(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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/* This gives us the lowest page that needs to be changed. */
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uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize);
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/* There is always a hole in the address space above the top of the
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stack. So when we make an mprotect call that spans past the top
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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 GROWSUP mapping to higher pages. */
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size_t size = GL(dl_pagesize) * 8;
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while (1)
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{
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if (__mprotect ((void *) page, size,
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PROT_READ|PROT_WRITE|PROT_EXEC) == 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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return errno;
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if (size == GL(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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return 0;
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}
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rtld_hidden_def (_dl_make_stack_executable)
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