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(no To-header on input) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Type: text/plain; charset="utf-8" This enables architectures using the generic mmap layout to support 32-bit mmap calls from 64-bit processes and vice-versa. Architectures using this must define separate 32-bit and 64-bit versions of STACK_TOP, TASK_UNMAPPED_BASE and STACK_RND_MASK. Signed-off-by: Amanieu d'Antras Co-developed-by: Ryan Houdek Signed-off-by: Ryan Houdek --- mm/util.c | 46 ++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 38 insertions(+), 8 deletions(-) diff --git a/mm/util.c b/mm/util.c index 54870226cea6..37bd764174b5 100644 --- a/mm/util.c +++ b/mm/util.c @@ -353,12 +353,12 @@ unsigned long arch_randomize_brk(struct mm_struct *mm) return randomize_page(mm->brk, SZ_1G); } =20 -unsigned long arch_mmap_rnd(void) +static unsigned long mmap_rnd(bool compat) { unsigned long rnd; =20 #ifdef CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS - if (is_compat_task()) + if (compat) rnd =3D get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1); else #endif /* CONFIG_HAVE_ARCH_MMAP_RND_COMPAT_BITS */ @@ -367,6 +367,11 @@ unsigned long arch_mmap_rnd(void) return rnd << PAGE_SHIFT; } =20 +unsigned long arch_mmap_rnd(void) +{ + return mmap_rnd(is_compat_task()); +} + static int mmap_is_legacy(struct rlimit *rlim_stack) { if (current->personality & ADDR_COMPAT_LAYOUT) @@ -383,16 +388,17 @@ static int mmap_is_legacy(struct rlimit *rlim_stack) * the face of randomisation. */ #define MIN_GAP (SZ_128M) -#define MAX_GAP (STACK_TOP / 6 * 5) +#define MAX_GAP (stack_top / 6 * 5) =20 -static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stac= k) +static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stac= k, + unsigned long stack_top, unsigned long stack_rnd_mask) { unsigned long gap =3D rlim_stack->rlim_cur; unsigned long pad =3D stack_guard_gap; =20 /* Account for stack randomization if necessary */ if (current->flags & PF_RANDOMIZE) - pad +=3D (STACK_RND_MASK << PAGE_SHIFT); + pad +=3D (stack_rnd_mask << PAGE_SHIFT); =20 /* Values close to RLIM_INFINITY can overflow. */ if (gap + pad > gap) @@ -403,21 +409,45 @@ static unsigned long mmap_base(unsigned long rnd, str= uct rlimit *rlim_stack) else if (gap > MAX_GAP) gap =3D MAX_GAP; =20 - return PAGE_ALIGN(STACK_TOP - gap - rnd); + return PAGE_ALIGN(stack_top - gap - rnd); } =20 void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) { unsigned long random_factor =3D 0UL; +#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES + unsigned long compat_random_factor =3D 0UL; +#endif =20 - if (current->flags & PF_RANDOMIZE) + if (current->flags & PF_RANDOMIZE) { +#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES + random_factor =3D mmap_rnd(false); + compat_random_factor =3D mmap_rnd(true); +#else random_factor =3D arch_mmap_rnd(); +#endif + } =20 if (mmap_is_legacy(rlim_stack)) { +#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES + mm->mmap_base =3D TASK_UNMAPPED_BASE_64 + random_factor; + mm->mmap_compat_base =3D + TASK_UNMAPPED_BASE_32 + compat_random_factor; +#else mm->mmap_base =3D TASK_UNMAPPED_BASE + random_factor; +#endif mm->get_unmapped_area =3D arch_get_unmapped_area; } else { - mm->mmap_base =3D mmap_base(random_factor, rlim_stack); +#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES + mm->mmap_base =3D mmap_base(random_factor, rlim_stack, + STACK_TOP_64, STACK_RND_MASK_64); + mm->mmap_compat_base =3D mmap_base(compat_random_factor, + rlim_stack, STACK_TOP_32, + STACK_RND_MASK_32); +#else + mm->mmap_base =3D mmap_base(random_factor, rlim_stack, STACK_TOP, + STACK_RND_MASK); +#endif mm->get_unmapped_area =3D arch_get_unmapped_area_topdown; } } --=20 2.31.1