lkml.org 
[lkml]   [2009]   [Sep]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v4] x86: increase MIN_GAP to include randomized stack
On Tue, 8 Sep 2009, Jiri Kosina wrote:

> > Currently we are not including randomized stack size when calculating
> > mmap_base address in arch_pick_mmap_layout for topdown case. This might
> > cause that mmap_base starts in the stack reserved area because stack is
> > randomized by 1GB for 64b (8MB for 32b) and the minimum gap is 128MB.
> >
> > If the stack really grows down to mmap_base then we can get silent mmap
> > region overwrite by the stack values.
> >
> > Let's include maximum stack randomization size into MIN_GAP which is
> > used as the low bound for the gap in mmap.
> >
> > Signed-off-by: Michal Hocko <mhocko@suse.cz>
>
> Acked-by: Jiri Kosina <jkosina@suse.cz>
>
> Ingo, could you please consider applying this?

Any comments about this patch please? (aka. "ping") :)

> > ---
> > arch/x86/include/asm/elf.h | 2 ++
> > arch/x86/mm/mmap.c | 17 +++++++++++++++--
> > 2 files changed, 17 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
> > index 83c1bc8..456a304 100644
> > --- a/arch/x86/include/asm/elf.h
> > +++ b/arch/x86/include/asm/elf.h
> > @@ -299,6 +299,8 @@ do { \
> >
> > #ifdef CONFIG_X86_32
> >
> > +#define STACK_RND_MASK (0x7ff)
> > +
> > #define VDSO_HIGH_BASE (__fix_to_virt(FIX_VDSO))
> >
> > #define ARCH_DLINFO ARCH_DLINFO_IA32(vdso_enabled)
> > diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
> > index 1658296..c8191de 100644
> > --- a/arch/x86/mm/mmap.c
> > +++ b/arch/x86/mm/mmap.c
> > @@ -29,13 +29,26 @@
> > #include <linux/random.h>
> > #include <linux/limits.h>
> > #include <linux/sched.h>
> > +#include <asm/elf.h>
> > +
> > +static unsigned int stack_maxrandom_size(void)
> > +{
> > + unsigned int max = 0;
> > + if ((current->flags & PF_RANDOMIZE) &&
> > + !(current->personality & ADDR_NO_RANDOMIZE)) {
> > + max = ((-1U) & STACK_RND_MASK) << PAGE_SHIFT;
> > + }
> > +
> > + return max;
> > +}
> > +
> >
> > /*
> > * Top of mmap area (just below the process stack).
> > *
> > - * Leave an at least ~128 MB hole.
> > + * Leave an at least ~128 MB hole with possible stack randomization.
> > */
> > -#define MIN_GAP (128*1024*1024)
> > +#define MIN_GAP (128*1024*1024UL + stack_maxrandom_size())
> > #define MAX_GAP (TASK_SIZE/6*5)
> >
> > /*
> > --
> > 1.6.3.3
> >

--
Jiri Kosina
SUSE Labs, Novell Inc.


\
 
 \ /
  Last update: 2009-09-11 01:17    [from the cache]
©2003-2011 Jasper Spaans