[v3,08/16] elf: Enable relro for static build
Commit Message
Changes from previous version:
- The tests were removed and instead I will use the ones proposed
by Florian's patch 'elf: Add tests for working RELRO protection'
[1]. I also plan to send additional coverage for '.data.rel.ro'
which trigger failures for the static case on both partial and
full relro which is fixed by this patch once the patch is
upstream.
--
The code is similar to the one at elf/dl-reloc.c, where it checks for
the l_relro_size from the link_map (obtained from PT_GNU_RELRO header
from program headers) and calls_dl_protected_relro.
Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
aarch64-linux-gnu, s390x-linux-gnu, and sparc64-linux-gnu. I also
check with --enable-static pie on x86_64-linux-gnu, i686-linux-gnu,
and aarch64-linux-gnu which seems the only architectures where
static PIE is actually working (as per 9d7a3741c9e, on
arm-linux-gnueabihf, powerpc64{le}-linux-gnu, and s390x-linux-gnu
I am seeing runtime issues not related to my patch).
[1] https://sourceware.org/ml/libc-alpha/2019-10/msg00059.html
---
elf/dl-support.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
Comments
On 18/12/19 3:17 am, Adhemerval Zanella wrote:
> Changes from previous version:
>
> - The tests were removed and instead I will use the ones proposed
> by Florian's patch 'elf: Add tests for working RELRO protection'
> [1]. I also plan to send additional coverage for '.data.rel.ro'
> which trigger failures for the static case on both partial and
> full relro which is fixed by this patch once the patch is
> upstream.
>
> --
>
> The code is similar to the one at elf/dl-reloc.c, where it checks for
> the l_relro_size from the link_map (obtained from PT_GNU_RELRO header
> from program headers) and calls_dl_protected_relro.
>
> Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
> aarch64-linux-gnu, s390x-linux-gnu, and sparc64-linux-gnu. I also
> check with --enable-static pie on x86_64-linux-gnu, i686-linux-gnu,
> and aarch64-linux-gnu which seems the only architectures where
> static PIE is actually working (as per 9d7a3741c9e, on
> arm-linux-gnueabihf, powerpc64{le}-linux-gnu, and s390x-linux-gnu
> I am seeing runtime issues not related to my patch).
>
> [1] https://sourceware.org/ml/libc-alpha/2019-10/msg00059.html
> ---
> elf/dl-support.c | 18 ++++++++++++++----
> 1 file changed, 14 insertions(+), 4 deletions(-)
>
OK.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
@@ -367,14 +367,24 @@ _dl_non_dynamic_init (void)
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)
+ for (const ElfW(Phdr) *ph = _dl_phdr; ph < &_dl_phdr[_dl_phnum]; ++ph)
+ switch (ph->p_type)
{
- _dl_stack_flags = _dl_phdr[i].p_flags;
+ /* Check if the stack is nonexecutable. */
+ case PT_GNU_STACK:
+ _dl_stack_flags = ph->p_flags;
+ break;
+
+ case PT_GNU_RELRO:
+ _dl_main_map.l_relro_addr = ph->p_vaddr;
+ _dl_main_map.l_relro_size = ph->p_memsz;
break;
}
+
+ /* Setup relro on the binary itself. */
+ if (_dl_main_map.l_relro_size != 0)
+ _dl_protect_relro (&_dl_main_map);
}
#ifdef DL_SYSINFO_IMPLEMENTATION