Messages in this thread | | | Subject | Re: [PATCH v6 09/14] mips: Properly account for stack randomization and stack guard gap | From | Sergei Shtylyov <> | Date | Thu, 8 Aug 2019 12:16:04 +0300 |
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Hello!
On 08.08.2019 9:17, Alexandre Ghiti 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://lkml.kernel.org/r/20170622200033.25714-1-riel@redhat.com > > Signed-off-by: Alexandre Ghiti <alex@ghiti.fr> > Acked-by: Kees Cook <keescook@chromium.org> > Acked-by: Paul Burton <paul.burton@mips.com> > Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> > --- > arch/mips/mm/mmap.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) > > diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c > index d79f2b432318..f5c778113384 100644 > --- a/arch/mips/mm/mmap.c > +++ b/arch/mips/mm/mmap.c > @@ -21,8 +21,9 @@ unsigned long shm_align_mask = PAGE_SIZE - 1; /* Sane caches */ > EXPORT_SYMBOL(shm_align_mask); > > /* gap between mmap and stack */ > -#define MIN_GAP (128*1024*1024UL) > -#define MAX_GAP ((TASK_SIZE)/6*5) > +#define MIN_GAP (128*1024*1024UL) > +#define MAX_GAP ((TASK_SIZE)/6*5)
Could add spaces around *, while touching this anyway? And parens around TASK_SIZE shouldn't be needed...
> +#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12)) > > static int mmap_is_legacy(struct rlimit *rlim_stack) > { > @@ -38,6 +39,15 @@ 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);
Parens not needed here.
> + > + /* Values close to RLIM_INFINITY can overflow. */ > + if (gap + pad > gap) > + gap += pad; > > if (gap < MIN_GAP) > gap = MIN_GAP; >
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