Messages in this thread | | | Date | Tue, 8 Sep 2009 10:47:46 +0200 (CEST) | From | Jiri Kosina <> | Subject | Re: [PATCH v3] x86: increase MIN_GAP to include randomized stack |
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On Tue, 8 Sep 2009, Michal Hocko 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> > --- > arch/x86/mm/mmap.c | 25 +++++++++++++++++++++++-- > 1 files changed, 23 insertions(+), 2 deletions(-) > > I think that this is also stable material and I will repost it to > stable@kernel.org once you ack it. > > Changes from v2: > STACK_RND_MASK has to be defined for CONFIG_X86_32 as well. > > Changes from v1: > Fixed unsigned int overflow in MIN_GAP calculation. > > > diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c > index 1658296..a4566a8 100644 > --- a/arch/x86/mm/mmap.c > +++ b/arch/x86/mm/mmap.c > @@ -30,12 +30,33 @@ > #include <linux/limits.h> > #include <linux/sched.h> > > +/* 1GB for 64bit, 8MB for 32bit definition taken from arch/x86/include/asm/elf.h */ > +#ifndef STACK_RND_MASK > +#ifdef CONFIG_X86_64 > +#define STACK_RND_MASK (test_thread_flag(TIF_IA32) ? 0x7ff : 0x3fffff) > +#else > +#define STACK_RND_MASK (0x7ff) > +#endif > +#endif
I'd still prefer all this macro-magic happening in <asm/elf.h> and including this file from arch/x86/mm/mmap.c, otherwise we are duplicating the STACK_RND_MASK definition, which is messy.
-- Jiri Kosina SUSE Labs
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