[PATCH] aarch64: Respect p_flags when protecting code with PROT_BTI

[Szabolcs Nagy]

The 07/17/2020 15:52, Szabolcs Nagy wrote:
> 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?

Carlos, is there any particular reason this is not approved for 2.32?


> > 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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