Messages in this thread | | | Date | Fri, 11 Sep 2009 01:14:13 +0200 (CEST) | From | Jiri Kosina <> | Subject | Re: [PATCH v4] x86: increase MIN_GAP to include randomized stack |
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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.
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