diff options
| -rw-r--r-- | elf/Versions | 1 | ||||
| -rw-r--r-- | elf/dl-load.c | 20 | ||||
| -rw-r--r-- | elf/dl-support.c | 19 | ||||
| -rw-r--r-- | elf/rtld.c | 11 | ||||
| -rw-r--r-- | sysdeps/generic/dl-execstack.c | 32 | ||||
| -rw-r--r-- | sysdeps/generic/ldsodefs.h | 13 | ||||
| -rw-r--r-- | sysdeps/unix/sysv/linux/dl-execstack.c | 115 |
7 files changed, 210 insertions, 1 deletions
diff --git a/elf/Versions b/elf/Versions index 7b07999..d3ed536 100644 --- a/elf/Versions +++ b/elf/Versions @@ -54,5 +54,6 @@ ld { _rtld_global; _dl_tls_symaddr; _dl_allocate_tls; _dl_deallocate_tls; _dl_get_tls_static_info; _dl_allocate_tls_init; _dl_get_origin; _dl_tls_setup; _dl_rtld_di_serinfo; + _dl_make_stack_executable; } } diff --git a/elf/dl-load.c b/elf/dl-load.c index 249ef84..0b6e96f 100644 --- a/elf/dl-load.c +++ b/elf/dl-load.c @@ -904,6 +904,9 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp, } } + /* Presumed absent PT_GNU_STACK. */ + uint_fast16_t stack_flags = PF_R|PF_W|PF_X; + { /* Scan the program header table, collecting its load commands. */ struct loadcmd @@ -1058,6 +1061,10 @@ cannot allocate TLS data structures for initial thread"); errstring = N_("cannot handle TLS data"); goto call_lose; break; + + case PT_GNU_STACK: + stack_flags = ph->p_flags; + break; } if (__builtin_expect (nloadcmds == 0, 0)) @@ -1334,6 +1341,19 @@ cannot allocate TLS data structures for initial thread"); l->l_dev = st.st_dev; l->l_ino = st.st_ino; + if (__builtin_expect ((stack_flags &~ GL(dl_stack_flags)) & PF_X, 0)) + { + /* The stack is presently not executable, but this module + requires that it be executable. */ + errval = (*GL(dl_make_stack_executable_hook)) (); + if (errval) + { + errstring = N_("\ +cannot enable executable stack as shared object requires"); + goto call_lose; + } + } + /* When we profile the SONAME might be needed for something else but loading. Add it right away. */ if (__builtin_expect (GL(dl_profile) != NULL, 0) diff --git a/elf/dl-support.c b/elf/dl-support.c index 8c58b2b..448f4c6 100644 --- a/elf/dl-support.c +++ b/elf/dl-support.c @@ -129,6 +129,16 @@ ElfW(Phdr) *_dl_phdr; size_t _dl_phnum; unsigned long int _dl_hwcap __attribute__ ((nocommon)); +/* Prevailing state of the stack, PF_X indicating it's executable. */ +ElfW(Word) _dl_stack_flags = PF_R|PF_W|PF_X; + +/* If loading a shared object requires that we make the stack executable + when it was not, we do it by calling this function. + It returns an errno code or zero on success. */ +int (*_dl_make_stack_executable_hook) (void) internal_function + = _dl_make_stack_executable; + + #ifdef NEED_DL_SYSINFO /* Needed for improved syscall handling on at least x86/Linux. */ uintptr_t _dl_sysinfo = DL_SYSINFO_DEFAULT; @@ -264,6 +274,15 @@ _dl_non_dynamic_init (void) /* Now determine the length of the platform string. */ if (_dl_platform != NULL) _dl_platformlen = strlen (_dl_platform); + + /* Scan for a program header telling us the stack is nonexecutable. */ + if (_dl_phdr != NULL) + for (uint_fast16_t i = 0; i < _dl_phnum; ++i) + if (_dl_phdr[i].p_type == PT_GNU_STACK) + { + _dl_stack_flags = _dl_phdr[i].p_flags; + break; + } } @@ -98,6 +98,8 @@ struct rtld_global _rtld_global = ._dl_fpu_control = _FPU_DEFAULT, ._dl_correct_cache_id = _DL_CACHE_DEFAULT_ID, ._dl_hwcap_mask = HWCAP_IMPORTANT, + /* Default presumption without further information is executable stack. */ + ._dl_stack_flags = PF_R|PF_W|PF_X, #ifdef _LIBC_REENTRANT ._dl_load_lock = _RTLD_LOCK_RECURSIVE_INITIALIZER #endif @@ -249,7 +251,7 @@ _dl_start_final (void *arg, struct dl_start_final_info *info) file access. It will call `dl_main' (below) to do all the real work of the dynamic linker, and then unwind our frame and run the user entry point on the same stack we entered on. */ - start_addr = _dl_sysdep_start (arg, &dl_main); + start_addr = _dl_sysdep_start (arg, &dl_main); #ifndef HP_TIMING_NONAVAIL if (HP_TIMING_AVAIL) @@ -903,6 +905,9 @@ of this helper program; chances are you did not intend to run this program.\n\ } break; #endif + case PT_GNU_STACK: + GL(dl_stack_flags) = ph->p_flags; + break; } #ifdef USE_TLS /* Adjust the address of the TLS initialization image in case @@ -949,6 +954,10 @@ of this helper program; chances are you did not intend to run this program.\n\ _exit (has_interp ? 0 : 2); } + /* The explicit initialization here is cheaper than processing the reloc + in the _rtld_local definition's initializer. */ + GL(dl_make_stack_executable_hook) = &_dl_make_stack_executable; + if (! rtld_is_main) /* Initialize the data structures for the search paths for shared objects. */ diff --git a/sysdeps/generic/dl-execstack.c b/sysdeps/generic/dl-execstack.c new file mode 100644 index 0000000..04f87cf --- /dev/null +++ b/sysdeps/generic/dl-execstack.c @@ -0,0 +1,32 @@ +/* Stack executability handling for GNU dynamic linker. Stub version. + Copyright (C) 2003 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, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <ldsodefs.h> +#include <errno.h> + +/* There is no portable way to know the bounds of the initial thread's stack + so as to mprotect it. */ + +int +internal_function +_dl_make_stack_executable (void) +{ + return ENOSYS; +} +rtld_hidden_def (_dl_make_stack_executable) diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index 58dfc15..afb1929 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -355,6 +355,14 @@ struct rtld_global EXTERN void (*_dl_rtld_unlock_recursive) (void *); #endif + /* Prevailing state of the stack, PF_X indicating it's executable. */ + EXTERN ElfW(Word) _dl_stack_flags; + + /* If loading a shared object requires that we make the stack executable + when it was not, we do it by calling this function. + It returns an errno code or zero on success. */ + EXTERN int (*_dl_make_stack_executable_hook) (void) internal_function; + /* Keep the conditional TLS members at the end so the layout of the structure used by !USE_TLS code matches the prefix of the layout in the USE_TLS rtld. Note that `struct link_map' is conditionally @@ -438,6 +446,11 @@ extern void **_dl_initial_error_catch_tsd (void) __attribute__ ((const)) attribute_hidden; #endif +/* This is the initial value of GL(dl_make_stack_executable_hook). + A threads library can change it. */ +extern int _dl_make_stack_executable (void) internal_function; +rtld_hidden_proto (_dl_make_stack_executable) + /* Parameters passed to the dynamic linker. */ extern int _dl_argc attribute_hidden; extern char **_dl_argv; diff --git a/sysdeps/unix/sysv/linux/dl-execstack.c b/sysdeps/unix/sysv/linux/dl-execstack.c new file mode 100644 index 0000000..42300b0 --- /dev/null +++ b/sysdeps/unix/sysv/linux/dl-execstack.c @@ -0,0 +1,115 @@ +/* Stack executability handling for GNU dynamic linker. Linux version. + Copyright (C) 2003 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, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <ldsodefs.h> +#include <sys/mman.h> +#include <errno.h> +#include <stdbool.h> +#include <stackinfo.h> + +extern void *__libc_stack_end; + +int +internal_function +_dl_make_stack_executable (void) +{ + if (__libc_stack_end == 0) + /* XXX for a DT_NEEDED library that requires the change, + this is not initialized yet! + */ + return ENOSYS; + +#if _STACK_GROWS_DOWN + /* This gives us the highest page that needs to be changed. */ + uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize); + + /* There is always a hole in the address space below the bottom of the + stack. So when we make an mprotect call that starts below the bottom + of the stack, it will include the hole and fail with ENOMEM. + + We start with a random guess at how deep the stack might have gotten + so as to have extended the GROWSDOWN mapping to lower pages. */ + + size_t size = GL(dl_pagesize) * 8; + page = page + GL(dl_pagesize) - size; + while (1) + { + if (__mprotect ((void *) page, size, + PROT_READ|PROT_WRITE|PROT_EXEC) == 0) + /* We got this chunk changed; loop to do another chunk below. */ + page -= size; + else + { + if (errno != ENOMEM) /* Unexpected failure mode. */ + return errno; + + if (size == GL(dl_pagesize)) + /* We just tried to mprotect the top hole page and failed. + We are done. */ + break; + + /* Our mprotect call failed because it started below the lowest + stack page. Try again on just the top half of that region. */ + size /= 2; + page += size; + } + } + +#elif _STACK_GROWS_UP + + /* This gives us the lowest page that needs to be changed. */ + uintptr_t page = (uintptr_t) __libc_stack_end & -(intptr_t) GL(dl_pagesize); + + /* There is always a hole in the address space above the top of the + stack. So when we make an mprotect call that spans past the top + of the stack, it will include the hole and fail with ENOMEM. + + We start with a random guess at how deep the stack might have gotten + so as to have extended the GROWSUP mapping to higher pages. */ + + size_t size = GL(dl_pagesize) * 8; + while (1) + { + if (__mprotect ((void *) page, size, + PROT_READ|PROT_WRITE|PROT_EXEC) == 0) + /* We got this chunk changed; loop to do another chunk below. */ + page += size; + else + { + if (errno != ENOMEM) /* Unexpected failure mode. */ + return errno; + + if (size == GL(dl_pagesize)) + /* We just tried to mprotect the lowest hole page and failed. + We are done. */ + break; + + /* Our mprotect call failed because it extended past the highest + stack page. Try again on just the bottom half of that region. */ + size /= 2; + } + } + +#else +# error "Define either _STACK_GROWS_DOWN or _STACK_GROWS_UP" +#endif + + return 0; +} +rtld_hidden_def (_dl_make_stack_executable) |