From 5cf7f9a0a54e93a6d3361de5f4ba4358b054c6c2 Mon Sep 17 00:00:00 2001 From: Christophe Leroy Date: Sat, 9 Apr 2022 19:17:35 +0200 Subject: [PATCH] powerpc/mm: Enable full randomisation of memory mappings Do like most other architectures and provide randomisation also to "legacy" memory mappings, by adding the random factor to mm->mmap_base in arch_pick_mmap_layout(). See commit 8b8addf891de ("x86/mm/32: Enable full randomization on i386 and X86_32") for all explanations and benefits of that mmap randomisation. At the moment, slice_find_area_bottomup() doesn't use mm->mmap_base but uses the fixed TASK_UNMAPPED_BASE instead. slice_find_area_bottomup() being used as a fallback to slice_find_area_topdown(), it can't use mm->mmap_base directly. Instead of always using TASK_UNMAPPED_BASE as base address, leave it to the caller. When called from slice_find_area_topdown() TASK_UNMAPPED_BASE is used. Otherwise mm->mmap_base is used. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/417fb10dde828534c73a03138b49621d74f4e5be.1649523076.git.christophe.leroy@csgroup.eu --- arch/powerpc/mm/book3s64/slice.c | 18 +++++++----------- arch/powerpc/mm/mmap.c | 2 +- 2 files changed, 8 insertions(+), 12 deletions(-) diff --git a/arch/powerpc/mm/book3s64/slice.c b/arch/powerpc/mm/book3s64/slice.c index 03681042b807..c0b58afb9a47 100644 --- a/arch/powerpc/mm/book3s64/slice.c +++ b/arch/powerpc/mm/book3s64/slice.c @@ -276,20 +276,18 @@ static bool slice_scan_available(unsigned long addr, } static unsigned long slice_find_area_bottomup(struct mm_struct *mm, - unsigned long len, + unsigned long addr, unsigned long len, const struct slice_mask *available, int psize, unsigned long high_limit) { int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT); - unsigned long addr, found, next_end; + unsigned long found, next_end; struct vm_unmapped_area_info info; info.flags = 0; info.length = len; info.align_mask = PAGE_MASK & ((1ul << pshift) - 1); info.align_offset = 0; - - addr = TASK_UNMAPPED_BASE; /* * Check till the allow max value for this mmap request */ @@ -322,12 +320,12 @@ static unsigned long slice_find_area_bottomup(struct mm_struct *mm, } static unsigned long slice_find_area_topdown(struct mm_struct *mm, - unsigned long len, + unsigned long addr, unsigned long len, const struct slice_mask *available, int psize, unsigned long high_limit) { int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT); - unsigned long addr, found, prev; + unsigned long found, prev; struct vm_unmapped_area_info info; unsigned long min_addr = max(PAGE_SIZE, mmap_min_addr); @@ -335,8 +333,6 @@ static unsigned long slice_find_area_topdown(struct mm_struct *mm, info.length = len; info.align_mask = PAGE_MASK & ((1ul << pshift) - 1); info.align_offset = 0; - - addr = mm->mmap_base; /* * If we are trying to allocate above DEFAULT_MAP_WINDOW * Add the different to the mmap_base. @@ -377,7 +373,7 @@ static unsigned long slice_find_area_topdown(struct mm_struct *mm, * can happen with large stack limits and large mmap() * allocations. */ - return slice_find_area_bottomup(mm, len, available, psize, high_limit); + return slice_find_area_bottomup(mm, TASK_UNMAPPED_BASE, len, available, psize, high_limit); } @@ -386,9 +382,9 @@ static unsigned long slice_find_area(struct mm_struct *mm, unsigned long len, int topdown, unsigned long high_limit) { if (topdown) - return slice_find_area_topdown(mm, len, mask, psize, high_limit); + return slice_find_area_topdown(mm, mm->mmap_base, len, mask, psize, high_limit); else - return slice_find_area_bottomup(mm, len, mask, psize, high_limit); + return slice_find_area_bottomup(mm, mm->mmap_base, len, mask, psize, high_limit); } static inline void slice_copy_mask(struct slice_mask *dst, diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c index 5972d619d274..d9eae456558a 100644 --- a/arch/powerpc/mm/mmap.c +++ b/arch/powerpc/mm/mmap.c @@ -96,7 +96,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) * bit is set, or if the expected stack growth is unlimited: */ if (mmap_is_legacy(rlim_stack)) { - mm->mmap_base = TASK_UNMAPPED_BASE; + mm->mmap_base = TASK_UNMAPPED_BASE + random_factor; mm->get_unmapped_area = arch_get_unmapped_area; } else { mm->mmap_base = mmap_base(random_factor, rlim_stack);