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glibc/sysdeps/aarch64/dl-bti.c

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aarch64: enable BTI at runtime Binaries can opt-in to using BTI via an ELF object file marking. The dynamic linker has to then mprotect the executable segments with PROT_BTI. In case of static linked executables or in case of the dynamic linker itself, PROT_BTI protection is done by the operating system. On AArch64 glibc uses PT_GNU_PROPERTY instead of PT_NOTE to check the properties of a binary because PT_NOTE can be unreliable with old linkers (old linkers just append the notes of input objects together and add them to the output without checking them for consistency which means multiple incompatible GNU property notes can be present in PT_NOTE). BTI property is handled in the loader even if glibc is not built with BTI support, so in theory user code can be BTI protected independently of glibc. In practice though user binaries are not marked with the BTI property if glibc has no support because the static linked libc objects (crt files, libc_nonshared.a) are unmarked. This patch relies on Linux userspace API that is not yet in a linux release but in v5.8-rc1 so scheduled to be in Linux 5.8. Co-authored-by: Szabolcs Nagy <szabolcs.nagy@arm.com> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-06-22 09:57:20 +00:00
/* AArch64 BTI functions.
Update copyright dates with scripts/update-copyrights
2024-01-01 18:12:26 +00:00
Copyright (C) 2020-2024 Free Software Foundation, Inc.
aarch64: enable BTI at runtime Binaries can opt-in to using BTI via an ELF object file marking. The dynamic linker has to then mprotect the executable segments with PROT_BTI. In case of static linked executables or in case of the dynamic linker itself, PROT_BTI protection is done by the operating system. On AArch64 glibc uses PT_GNU_PROPERTY instead of PT_NOTE to check the properties of a binary because PT_NOTE can be unreliable with old linkers (old linkers just append the notes of input objects together and add them to the output without checking them for consistency which means multiple incompatible GNU property notes can be present in PT_NOTE). BTI property is handled in the loader even if glibc is not built with BTI support, so in theory user code can be BTI protected independently of glibc. In practice though user binaries are not marked with the BTI property if glibc has no support because the static linked libc objects (crt files, libc_nonshared.a) are unmarked. This patch relies on Linux userspace API that is not yet in a linux release but in v5.8-rc1 so scheduled to be in Linux 5.8. Co-authored-by: Szabolcs Nagy <szabolcs.nagy@arm.com> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-06-22 09:57:20 +00:00
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 <unistd.h>
#include <errno.h>
#include <libintl.h>
#include <ldsodefs.h>
aarch64: Use mmap to add PROT_BTI instead of mprotect [BZ #26831] Re-mmap executable segments if possible instead of using mprotect to add PROT_BTI. This allows using BTI protection with security policies that prevent mprotect with PROT_EXEC. If the fd of the ELF module is not available because it was kernel mapped then mprotect is used and failures are ignored. To protect the main executable even when mprotect is filtered the linux kernel will have to be changed to add PROT_BTI to it. The delayed failure reporting is mainly needed because currently _dl_process_gnu_properties does not propagate failures such that the required cleanups happen. Using the link_map_machine struct for error propagation is not ideal, but this seemed to be the least intrusive solution. Fixes bug 26831. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-12-01 10:13:18 +00:00
#include <sys/mman.h>
aarch64: enable BTI at runtime Binaries can opt-in to using BTI via an ELF object file marking. The dynamic linker has to then mprotect the executable segments with PROT_BTI. In case of static linked executables or in case of the dynamic linker itself, PROT_BTI protection is done by the operating system. On AArch64 glibc uses PT_GNU_PROPERTY instead of PT_NOTE to check the properties of a binary because PT_NOTE can be unreliable with old linkers (old linkers just append the notes of input objects together and add them to the output without checking them for consistency which means multiple incompatible GNU property notes can be present in PT_NOTE). BTI property is handled in the loader even if glibc is not built with BTI support, so in theory user code can be BTI protected independently of glibc. In practice though user binaries are not marked with the BTI property if glibc has no support because the static linked libc objects (crt files, libc_nonshared.a) are unmarked. This patch relies on Linux userspace API that is not yet in a linux release but in v5.8-rc1 so scheduled to be in Linux 5.8. Co-authored-by: Szabolcs Nagy <szabolcs.nagy@arm.com> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-06-22 09:57:20 +00:00
aarch64: Use mmap to add PROT_BTI instead of mprotect [BZ #26831] Re-mmap executable segments if possible instead of using mprotect to add PROT_BTI. This allows using BTI protection with security policies that prevent mprotect with PROT_EXEC. If the fd of the ELF module is not available because it was kernel mapped then mprotect is used and failures are ignored. To protect the main executable even when mprotect is filtered the linux kernel will have to be changed to add PROT_BTI to it. The delayed failure reporting is mainly needed because currently _dl_process_gnu_properties does not propagate failures such that the required cleanups happen. Using the link_map_machine struct for error propagation is not ideal, but this seemed to be the least intrusive solution. Fixes bug 26831. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-12-01 10:13:18 +00:00
/* See elf/dl-load.h. */
#ifndef MAP_COPY
# define MAP_COPY (MAP_PRIVATE | MAP_DENYWRITE)
#endif
/* Enable BTI protection for MAP. */
void
_dl_bti_protect (struct link_map *map, int fd)
aarch64: enable BTI at runtime Binaries can opt-in to using BTI via an ELF object file marking. The dynamic linker has to then mprotect the executable segments with PROT_BTI. In case of static linked executables or in case of the dynamic linker itself, PROT_BTI protection is done by the operating system. On AArch64 glibc uses PT_GNU_PROPERTY instead of PT_NOTE to check the properties of a binary because PT_NOTE can be unreliable with old linkers (old linkers just append the notes of input objects together and add them to the output without checking them for consistency which means multiple incompatible GNU property notes can be present in PT_NOTE). BTI property is handled in the loader even if glibc is not built with BTI support, so in theory user code can be BTI protected independently of glibc. In practice though user binaries are not marked with the BTI property if glibc has no support because the static linked libc objects (crt files, libc_nonshared.a) are unmarked. This patch relies on Linux userspace API that is not yet in a linux release but in v5.8-rc1 so scheduled to be in Linux 5.8. Co-authored-by: Szabolcs Nagy <szabolcs.nagy@arm.com> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-06-22 09:57:20 +00:00
{
aarch64: align address for BTI protection [BZ #26988] Handle unaligned executable load segments (the bfd linker is not expected to produce such binaries, but other linkers may). Computing the mapping bounds follows _dl_map_object_from_fd more closely now. Fixes bug 26988. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-12-01 10:12:32 +00:00
const size_t pagesz = GLRO(dl_pagesize);
aarch64: enable BTI at runtime Binaries can opt-in to using BTI via an ELF object file marking. The dynamic linker has to then mprotect the executable segments with PROT_BTI. In case of static linked executables or in case of the dynamic linker itself, PROT_BTI protection is done by the operating system. On AArch64 glibc uses PT_GNU_PROPERTY instead of PT_NOTE to check the properties of a binary because PT_NOTE can be unreliable with old linkers (old linkers just append the notes of input objects together and add them to the output without checking them for consistency which means multiple incompatible GNU property notes can be present in PT_NOTE). BTI property is handled in the loader even if glibc is not built with BTI support, so in theory user code can be BTI protected independently of glibc. In practice though user binaries are not marked with the BTI property if glibc has no support because the static linked libc objects (crt files, libc_nonshared.a) are unmarked. This patch relies on Linux userspace API that is not yet in a linux release but in v5.8-rc1 so scheduled to be in Linux 5.8. Co-authored-by: Szabolcs Nagy <szabolcs.nagy@arm.com> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-06-22 09:57:20 +00:00
const ElfW(Phdr) *phdr;
for (phdr = map->l_phdr; phdr < &map->l_phdr[map->l_phnum]; ++phdr)
if (phdr->p_type == PT_LOAD && (phdr->p_flags & PF_X))
{
aarch64: align address for BTI protection [BZ #26988] Handle unaligned executable load segments (the bfd linker is not expected to produce such binaries, but other linkers may). Computing the mapping bounds follows _dl_map_object_from_fd more closely now. Fixes bug 26988. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-12-01 10:12:32 +00:00
size_t vstart = ALIGN_DOWN (phdr->p_vaddr, pagesz);
size_t vend = ALIGN_UP (phdr->p_vaddr + phdr->p_filesz, pagesz);
off_t off = ALIGN_DOWN (phdr->p_offset, pagesz);
void *start = (void *) (vstart + map->l_addr);
size_t len = vend - vstart;
aarch64: Respect p_flags when protecting code with PROT_BTI Use PROT_READ and PROT_WRITE according to the load segment p_flags when adding PROT_BTI. This is before processing relocations which may drop PROT_BTI in case of textrels. Executable stacks are not protected via PROT_BTI either. PROT_BTI is hardening in case memory corruption happened, it's value is reduced if there is writable and executable memory available so missing it on such memory is fine, but we should respect the p_flags and should not drop PROT_WRITE.
2020-07-13 10:28:18 +00:00
aarch64: align address for BTI protection [BZ #26988] Handle unaligned executable load segments (the bfd linker is not expected to produce such binaries, but other linkers may). Computing the mapping bounds follows _dl_map_object_from_fd more closely now. Fixes bug 26988. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-12-01 10:12:32 +00:00
unsigned prot = PROT_EXEC | PROT_BTI;
aarch64: Respect p_flags when protecting code with PROT_BTI Use PROT_READ and PROT_WRITE according to the load segment p_flags when adding PROT_BTI. This is before processing relocations which may drop PROT_BTI in case of textrels. Executable stacks are not protected via PROT_BTI either. PROT_BTI is hardening in case memory corruption happened, it's value is reduced if there is writable and executable memory available so missing it on such memory is fine, but we should respect the p_flags and should not drop PROT_WRITE.
2020-07-13 10:28:18 +00:00
if (phdr->p_flags & PF_R)
prot |= PROT_READ;
if (phdr->p_flags & PF_W)
prot |= PROT_WRITE;
aarch64: Use mmap to add PROT_BTI instead of mprotect [BZ #26831] Re-mmap executable segments if possible instead of using mprotect to add PROT_BTI. This allows using BTI protection with security policies that prevent mprotect with PROT_EXEC. If the fd of the ELF module is not available because it was kernel mapped then mprotect is used and failures are ignored. To protect the main executable even when mprotect is filtered the linux kernel will have to be changed to add PROT_BTI to it. The delayed failure reporting is mainly needed because currently _dl_process_gnu_properties does not propagate failures such that the required cleanups happen. Using the link_map_machine struct for error propagation is not ideal, but this seemed to be the least intrusive solution. Fixes bug 26831. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-12-01 10:13:18 +00:00
if (fd == -1)
/* Ignore failures for kernel mapped binaries. */
__mprotect (start, len, prot);
else
map->l_mach.bti_fail = __mmap (start, len, prot,
MAP_FIXED|MAP_COPY|MAP_FILE,
fd, off) == MAP_FAILED;
aarch64: enable BTI at runtime Binaries can opt-in to using BTI via an ELF object file marking. The dynamic linker has to then mprotect the executable segments with PROT_BTI. In case of static linked executables or in case of the dynamic linker itself, PROT_BTI protection is done by the operating system. On AArch64 glibc uses PT_GNU_PROPERTY instead of PT_NOTE to check the properties of a binary because PT_NOTE can be unreliable with old linkers (old linkers just append the notes of input objects together and add them to the output without checking them for consistency which means multiple incompatible GNU property notes can be present in PT_NOTE). BTI property is handled in the loader even if glibc is not built with BTI support, so in theory user code can be BTI protected independently of glibc. In practice though user binaries are not marked with the BTI property if glibc has no support because the static linked libc objects (crt files, libc_nonshared.a) are unmarked. This patch relies on Linux userspace API that is not yet in a linux release but in v5.8-rc1 so scheduled to be in Linux 5.8. Co-authored-by: Szabolcs Nagy <szabolcs.nagy@arm.com> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-06-22 09:57:20 +00:00
}
}
aarch64: Use mmap to add PROT_BTI instead of mprotect [BZ #26831] Re-mmap executable segments if possible instead of using mprotect to add PROT_BTI. This allows using BTI protection with security policies that prevent mprotect with PROT_EXEC. If the fd of the ELF module is not available because it was kernel mapped then mprotect is used and failures are ignored. To protect the main executable even when mprotect is filtered the linux kernel will have to be changed to add PROT_BTI to it. The delayed failure reporting is mainly needed because currently _dl_process_gnu_properties does not propagate failures such that the required cleanups happen. Using the link_map_machine struct for error propagation is not ideal, but this seemed to be the least intrusive solution. Fixes bug 26831. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-12-01 10:13:18 +00:00
static void
bti_failed (struct link_map *l, const char *program)
{
if (program)
_dl_fatal_printf ("%s: %s: failed to turn on BTI protection\n",
program, l->l_name);
else
/* Note: the errno value is not available any more. */
_dl_signal_error (0, l->l_name, "dlopen",
N_("failed to turn on BTI protection"));
}
aarch64: Fix missing BTI protection from dependencies [BZ #26926] The _dl_open_check and _rtld_main_check hooks are not called on the dependencies of a loaded module, so BTI protection was missed on every module other than the main executable and directly dlopened libraries. The fix just iterates over dependencies to enable BTI. Fixes bug 26926.
2020-11-20 15:27:06 +00:00
/* Enable BTI for L and its dependencies. */
aarch64: enable BTI at runtime Binaries can opt-in to using BTI via an ELF object file marking. The dynamic linker has to then mprotect the executable segments with PROT_BTI. In case of static linked executables or in case of the dynamic linker itself, PROT_BTI protection is done by the operating system. On AArch64 glibc uses PT_GNU_PROPERTY instead of PT_NOTE to check the properties of a binary because PT_NOTE can be unreliable with old linkers (old linkers just append the notes of input objects together and add them to the output without checking them for consistency which means multiple incompatible GNU property notes can be present in PT_NOTE). BTI property is handled in the loader even if glibc is not built with BTI support, so in theory user code can be BTI protected independently of glibc. In practice though user binaries are not marked with the BTI property if glibc has no support because the static linked libc objects (crt files, libc_nonshared.a) are unmarked. This patch relies on Linux userspace API that is not yet in a linux release but in v5.8-rc1 so scheduled to be in Linux 5.8. Co-authored-by: Szabolcs Nagy <szabolcs.nagy@arm.com> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-06-22 09:57:20 +00:00
void
_dl_bti_check (struct link_map *l, const char *program)
{
aarch64: Fix missing BTI protection from dependencies [BZ #26926] The _dl_open_check and _rtld_main_check hooks are not called on the dependencies of a loaded module, so BTI protection was missed on every module other than the main executable and directly dlopened libraries. The fix just iterates over dependencies to enable BTI. Fixes bug 26926.
2020-11-20 15:27:06 +00:00
if (!GLRO(dl_aarch64_cpu_features).bti)
return;
aarch64: Use mmap to add PROT_BTI instead of mprotect [BZ #26831] Re-mmap executable segments if possible instead of using mprotect to add PROT_BTI. This allows using BTI protection with security policies that prevent mprotect with PROT_EXEC. If the fd of the ELF module is not available because it was kernel mapped then mprotect is used and failures are ignored. To protect the main executable even when mprotect is filtered the linux kernel will have to be changed to add PROT_BTI to it. The delayed failure reporting is mainly needed because currently _dl_process_gnu_properties does not propagate failures such that the required cleanups happen. Using the link_map_machine struct for error propagation is not ideal, but this seemed to be the least intrusive solution. Fixes bug 26831. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-12-01 10:13:18 +00:00
if (l->l_mach.bti_fail)
bti_failed (l, program);
aarch64: Fix missing BTI protection from dependencies [BZ #26926] The _dl_open_check and _rtld_main_check hooks are not called on the dependencies of a loaded module, so BTI protection was missed on every module other than the main executable and directly dlopened libraries. The fix just iterates over dependencies to enable BTI. Fixes bug 26926.
2020-11-20 15:27:06 +00:00
unsigned int i = l->l_searchlist.r_nlist;
while (i-- > 0)
{
struct link_map *dep = l->l_initfini[i];
aarch64: Use mmap to add PROT_BTI instead of mprotect [BZ #26831] Re-mmap executable segments if possible instead of using mprotect to add PROT_BTI. This allows using BTI protection with security policies that prevent mprotect with PROT_EXEC. If the fd of the ELF module is not available because it was kernel mapped then mprotect is used and failures are ignored. To protect the main executable even when mprotect is filtered the linux kernel will have to be changed to add PROT_BTI to it. The delayed failure reporting is mainly needed because currently _dl_process_gnu_properties does not propagate failures such that the required cleanups happen. Using the link_map_machine struct for error propagation is not ideal, but this seemed to be the least intrusive solution. Fixes bug 26831. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-12-01 10:13:18 +00:00
if (dep->l_mach.bti_fail)
bti_failed (dep, program);
aarch64: Fix missing BTI protection from dependencies [BZ #26926] The _dl_open_check and _rtld_main_check hooks are not called on the dependencies of a loaded module, so BTI protection was missed on every module other than the main executable and directly dlopened libraries. The fix just iterates over dependencies to enable BTI. Fixes bug 26926.
2020-11-20 15:27:06 +00:00
}
aarch64: enable BTI at runtime Binaries can opt-in to using BTI via an ELF object file marking. The dynamic linker has to then mprotect the executable segments with PROT_BTI. In case of static linked executables or in case of the dynamic linker itself, PROT_BTI protection is done by the operating system. On AArch64 glibc uses PT_GNU_PROPERTY instead of PT_NOTE to check the properties of a binary because PT_NOTE can be unreliable with old linkers (old linkers just append the notes of input objects together and add them to the output without checking them for consistency which means multiple incompatible GNU property notes can be present in PT_NOTE). BTI property is handled in the loader even if glibc is not built with BTI support, so in theory user code can be BTI protected independently of glibc. In practice though user binaries are not marked with the BTI property if glibc has no support because the static linked libc objects (crt files, libc_nonshared.a) are unmarked. This patch relies on Linux userspace API that is not yet in a linux release but in v5.8-rc1 so scheduled to be in Linux 5.8. Co-authored-by: Szabolcs Nagy <szabolcs.nagy@arm.com> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
2020-06-22 09:57:20 +00:00
}
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