[PATCH] aarch64: Respect p_flags when protecting code with PROT_BTI
Szabolcs Nagy
szabolcs.nagy@arm.com
Fri Jul 17 14:52:19 GMT 2020
The 07/15/2020 16:44, Szabolcs Nagy wrote:
> i'd like to commit the attached patch for 2.32
ping.
or can i commit such a patch as a bug fix?
> From af3c11a811cfcc2b72f07efa0696c2200e928e12 Mon Sep 17 00:00:00 2001
> From: Szabolcs Nagy <szabolcs.nagy@arm.com>
> Date: Mon, 13 Jul 2020 11:28:18 +0100
> Subject: [PATCH] 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.
> ---
> sysdeps/aarch64/dl-bti.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/sysdeps/aarch64/dl-bti.c b/sysdeps/aarch64/dl-bti.c
> index 965ddcc732..196e462520 100644
> --- a/sysdeps/aarch64/dl-bti.c
> +++ b/sysdeps/aarch64/dl-bti.c
> @@ -24,13 +24,20 @@ static int
> enable_bti (struct link_map *map, const char *program)
> {
> const ElfW(Phdr) *phdr;
> - unsigned prot = PROT_READ | PROT_EXEC | PROT_BTI;
> + unsigned prot;
>
> for (phdr = map->l_phdr; phdr < &map->l_phdr[map->l_phnum]; ++phdr)
> if (phdr->p_type == PT_LOAD && (phdr->p_flags & PF_X))
> {
> void *start = (void *) (phdr->p_vaddr + map->l_addr);
> size_t len = phdr->p_memsz;
> +
> + prot = PROT_EXEC | PROT_BTI;
> + if (phdr->p_flags & PF_R)
> + prot |= PROT_READ;
> + if (phdr->p_flags & PF_W)
> + prot |= PROT_WRITE;
> +
> if (__mprotect (start, len, prot) < 0)
> {
> if (program)
> --
> 2.17.1
>
--
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