Messages in this thread | | | Subject | Re: [PATCH v3 05/11] arm: Properly account for stack randomization and stack guard gap | From | Alex Ghiti <> | Date | Thu, 18 Apr 2019 02:01:20 -0400 |
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On 4/18/19 1:26 AM, Kees Cook wrote: > On Wed, Apr 17, 2019 at 12:28 AM Alexandre Ghiti <alex@ghiti.fr> wrote: >> This commit takes care of stack randomization and stack guard gap when >> computing mmap base address and checks if the task asked for randomization. >> This fixes the problem uncovered and not fixed for arm here: >> https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1429066.html > Please use the official archive instead. This includes headers, linked > patches, etc: > https://lkml.kernel.org/r/20170622200033.25714-1-riel@redhat.com
Ok, sorry about that, and thanks for the info.
> >> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> >> --- >> arch/arm/mm/mmap.c | 14 ++++++++++++-- >> 1 file changed, 12 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c >> index f866870db749..bff3d00bda5b 100644 >> --- a/arch/arm/mm/mmap.c >> +++ b/arch/arm/mm/mmap.c >> @@ -18,8 +18,9 @@ >> (((pgoff)<<PAGE_SHIFT) & (SHMLBA-1))) >> >> /* gap between mmap and stack */ >> -#define MIN_GAP (128*1024*1024UL) >> -#define MAX_GAP ((TASK_SIZE)/6*5) >> +#define MIN_GAP (128*1024*1024UL) > Might as well fix this up as SIZE_128M
I left the code as is because it gets removed in the next commit, I did not even correct the checkpatch warnings. But I can fix that in v4, since there will be a v4 :)
> >> +#define MAX_GAP ((TASK_SIZE)/6*5) >> +#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12)) > STACK_RND_MASK is already defined so you don't need to add it here, yes?
At this point, I don't think arm has STACK_RND_MASK defined anywhere since the generic version is in mm/util.c.
> >> static int mmap_is_legacy(struct rlimit *rlim_stack) >> { >> @@ -35,6 +36,15 @@ static int mmap_is_legacy(struct rlimit *rlim_stack) >> static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack) >> { >> unsigned long gap = rlim_stack->rlim_cur; >> + unsigned long pad = stack_guard_gap; >> + >> + /* Account for stack randomization if necessary */ >> + if (current->flags & PF_RANDOMIZE) >> + pad += (STACK_RND_MASK << PAGE_SHIFT); >> + >> + /* Values close to RLIM_INFINITY can overflow. */ >> + if (gap + pad > gap) >> + gap += pad; >> >> if (gap < MIN_GAP) >> gap = MIN_GAP; >> -- >> 2.20.1 >> > But otherwise, yes: > > Acked-by: Kees Cook <keescook@chromium.org>
Thanks !
> > -- > Kees Cook > > _______________________________________________ > linux-riscv mailing list > linux-riscv@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-riscv
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