diff options
Diffstat (limited to 'main/linux-vanilla/mm-larger-stack-guard-gap-between-vmas.patch')
| -rw-r--r-- | main/linux-vanilla/mm-larger-stack-guard-gap-between-vmas.patch | 885 |
1 files changed, 885 insertions, 0 deletions
diff --git a/main/linux-vanilla/mm-larger-stack-guard-gap-between-vmas.patch b/main/linux-vanilla/mm-larger-stack-guard-gap-between-vmas.patch new file mode 100644 index 0000000000..af4e9c6980 --- /dev/null +++ b/main/linux-vanilla/mm-larger-stack-guard-gap-between-vmas.patch @@ -0,0 +1,885 @@ +From: Hugh Dickins <hughd@google.com> +Date: Mon, 19 Jun 2017 04:03:24 -0700 +Subject: mm: larger stack guard gap, between vmas + +commit 1be7107fbe18eed3e319a6c3e83c78254b693acb upstream. + +Stack guard page is a useful feature to reduce a risk of stack smashing +into a different mapping. We have been using a single page gap which +is sufficient to prevent having stack adjacent to a different mapping. +But this seems to be insufficient in the light of the stack usage in +userspace. E.g. glibc uses as large as 64kB alloca() in many commonly +used functions. Others use constructs liks gid_t buffer[NGROUPS_MAX] +which is 256kB or stack strings with MAX_ARG_STRLEN. + +This will become especially dangerous for suid binaries and the default +no limit for the stack size limit because those applications can be +tricked to consume a large portion of the stack and a single glibc call +could jump over the guard page. These attacks are not theoretical, +unfortunatelly. + +Make those attacks less probable by increasing the stack guard gap +to 1MB (on systems with 4k pages; but make it depend on the page size +because systems with larger base pages might cap stack allocations in +the PAGE_SIZE units) which should cover larger alloca() and VLA stack +allocations. It is obviously not a full fix because the problem is +somehow inherent, but it should reduce attack space a lot. + +One could argue that the gap size should be configurable from userspace, +but that can be done later when somebody finds that the new 1MB is wrong +for some special case applications. For now, add a kernel command line +option (stack_guard_gap) to specify the stack gap size (in page units). + +Implementation wise, first delete all the old code for stack guard page: +because although we could get away with accounting one extra page in a +stack vma, accounting a larger gap can break userspace - case in point, +a program run with "ulimit -S -v 20000" failed when the 1MB gap was +counted for RLIMIT_AS; similar problems could come with RLIMIT_MLOCK +and strict non-overcommit mode. + +Instead of keeping gap inside the stack vma, maintain the stack guard +gap as a gap between vmas: using vm_start_gap() in place of vm_start +(or vm_end_gap() in place of vm_end if VM_GROWSUP) in just those few +places which need to respect the gap - mainly arch_get_unmapped_area(), +and and the vma tree's subtree_gap support for that. + +Original-patch-by: Oleg Nesterov <oleg@redhat.com> +Original-patch-by: Michal Hocko <mhocko@suse.com> +Signed-off-by: Hugh Dickins <hughd@google.com> +Acked-by: Michal Hocko <mhocko@suse.com> +Tested-by: Helge Deller <deller@gmx.de> # parisc +Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> +[wt: backport to 4.11: adjust context] +[wt: backport to 4.9: adjust context ; kernel doc was not in admin-guide] +Signed-off-by: Willy Tarreau <w@1wt.eu> +Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> +--- + Documentation/kernel-parameters.txt | 7 + + arch/arc/mm/mmap.c | 2 + arch/arm/mm/mmap.c | 4 + arch/frv/mm/elf-fdpic.c | 2 + arch/mips/mm/mmap.c | 2 + arch/parisc/kernel/sys_parisc.c | 15 ++- + arch/powerpc/mm/hugetlbpage-radix.c | 2 + arch/powerpc/mm/mmap.c | 4 + arch/powerpc/mm/slice.c | 2 + arch/s390/mm/mmap.c | 4 + arch/sh/mm/mmap.c | 4 + arch/sparc/kernel/sys_sparc_64.c | 4 + arch/sparc/mm/hugetlbpage.c | 2 + arch/tile/mm/hugetlbpage.c | 2 + arch/x86/kernel/sys_x86_64.c | 4 + arch/x86/mm/hugetlbpage.c | 2 + arch/xtensa/kernel/syscall.c | 2 + fs/hugetlbfs/inode.c | 2 + fs/proc/task_mmu.c | 4 + include/linux/mm.h | 53 ++++++------ + mm/gup.c | 5 - + mm/memory.c | 38 --------- + mm/mmap.c | 149 +++++++++++++++++++++--------------- + 23 files changed, 152 insertions(+), 163 deletions(-) + +--- a/Documentation/kernel-parameters.txt ++++ b/Documentation/kernel-parameters.txt +@@ -3932,6 +3932,13 @@ bytes respectively. Such letter suffixes + spia_pedr= + spia_peddr= + ++ stack_guard_gap= [MM] ++ override the default stack gap protection. The value ++ is in page units and it defines how many pages prior ++ to (for stacks growing down) resp. after (for stacks ++ growing up) the main stack are reserved for no other ++ mapping. Default value is 256 pages. ++ + stacktrace [FTRACE] + Enabled the stack tracer on boot up. + +--- a/arch/arc/mm/mmap.c ++++ b/arch/arc/mm/mmap.c +@@ -64,7 +64,7 @@ arch_get_unmapped_area(struct file *filp + + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + +--- a/arch/arm/mm/mmap.c ++++ b/arch/arm/mm/mmap.c +@@ -89,7 +89,7 @@ arch_get_unmapped_area(struct file *filp + + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + +@@ -140,7 +140,7 @@ arch_get_unmapped_area_topdown(struct fi + addr = PAGE_ALIGN(addr); + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + +--- a/arch/frv/mm/elf-fdpic.c ++++ b/arch/frv/mm/elf-fdpic.c +@@ -74,7 +74,7 @@ unsigned long arch_get_unmapped_area(str + addr = PAGE_ALIGN(addr); + vma = find_vma(current->mm, addr); + if (TASK_SIZE - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + goto success; + } + +--- a/arch/mips/mm/mmap.c ++++ b/arch/mips/mm/mmap.c +@@ -92,7 +92,7 @@ static unsigned long arch_get_unmapped_a + + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + +--- a/arch/parisc/kernel/sys_parisc.c ++++ b/arch/parisc/kernel/sys_parisc.c +@@ -88,7 +88,7 @@ unsigned long arch_get_unmapped_area(str + unsigned long len, unsigned long pgoff, unsigned long flags) + { + struct mm_struct *mm = current->mm; +- struct vm_area_struct *vma; ++ struct vm_area_struct *vma, *prev; + unsigned long task_size = TASK_SIZE; + int do_color_align, last_mmap; + struct vm_unmapped_area_info info; +@@ -115,9 +115,10 @@ unsigned long arch_get_unmapped_area(str + else + addr = PAGE_ALIGN(addr); + +- vma = find_vma(mm, addr); ++ vma = find_vma_prev(mm, addr, &prev); + if (task_size - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma)) && ++ (!prev || addr >= vm_end_gap(prev))) + goto found_addr; + } + +@@ -141,7 +142,7 @@ arch_get_unmapped_area_topdown(struct fi + const unsigned long len, const unsigned long pgoff, + const unsigned long flags) + { +- struct vm_area_struct *vma; ++ struct vm_area_struct *vma, *prev; + struct mm_struct *mm = current->mm; + unsigned long addr = addr0; + int do_color_align, last_mmap; +@@ -175,9 +176,11 @@ arch_get_unmapped_area_topdown(struct fi + addr = COLOR_ALIGN(addr, last_mmap, pgoff); + else + addr = PAGE_ALIGN(addr); +- vma = find_vma(mm, addr); ++ ++ vma = find_vma_prev(mm, addr, &prev); + if (TASK_SIZE - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma)) && ++ (!prev || addr >= vm_end_gap(prev))) + goto found_addr; + } + +--- a/arch/powerpc/mm/hugetlbpage-radix.c ++++ b/arch/powerpc/mm/hugetlbpage-radix.c +@@ -65,7 +65,7 @@ radix__hugetlb_get_unmapped_area(struct + addr = ALIGN(addr, huge_page_size(h)); + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + /* +--- a/arch/powerpc/mm/mmap.c ++++ b/arch/powerpc/mm/mmap.c +@@ -106,7 +106,7 @@ radix__arch_get_unmapped_area(struct fil + addr = PAGE_ALIGN(addr); + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + +@@ -142,7 +142,7 @@ radix__arch_get_unmapped_area_topdown(st + addr = PAGE_ALIGN(addr); + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + +--- a/arch/powerpc/mm/slice.c ++++ b/arch/powerpc/mm/slice.c +@@ -105,7 +105,7 @@ static int slice_area_is_free(struct mm_ + if ((mm->task_size - len) < addr) + return 0; + vma = find_vma(mm, addr); +- return (!vma || (addr + len) <= vma->vm_start); ++ return (!vma || (addr + len) <= vm_start_gap(vma)); + } + + static int slice_low_has_vma(struct mm_struct *mm, unsigned long slice) +--- a/arch/s390/mm/mmap.c ++++ b/arch/s390/mm/mmap.c +@@ -98,7 +98,7 @@ arch_get_unmapped_area(struct file *filp + addr = PAGE_ALIGN(addr); + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + +@@ -136,7 +136,7 @@ arch_get_unmapped_area_topdown(struct fi + addr = PAGE_ALIGN(addr); + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + +--- a/arch/sh/mm/mmap.c ++++ b/arch/sh/mm/mmap.c +@@ -63,7 +63,7 @@ unsigned long arch_get_unmapped_area(str + + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + +@@ -113,7 +113,7 @@ arch_get_unmapped_area_topdown(struct fi + + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + +--- a/arch/sparc/kernel/sys_sparc_64.c ++++ b/arch/sparc/kernel/sys_sparc_64.c +@@ -118,7 +118,7 @@ unsigned long arch_get_unmapped_area(str + + vma = find_vma(mm, addr); + if (task_size - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + +@@ -181,7 +181,7 @@ arch_get_unmapped_area_topdown(struct fi + + vma = find_vma(mm, addr); + if (task_size - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + +--- a/arch/sparc/mm/hugetlbpage.c ++++ b/arch/sparc/mm/hugetlbpage.c +@@ -116,7 +116,7 @@ hugetlb_get_unmapped_area(struct file *f + addr = ALIGN(addr, HPAGE_SIZE); + vma = find_vma(mm, addr); + if (task_size - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + if (mm->get_unmapped_area == arch_get_unmapped_area) +--- a/arch/tile/mm/hugetlbpage.c ++++ b/arch/tile/mm/hugetlbpage.c +@@ -232,7 +232,7 @@ unsigned long hugetlb_get_unmapped_area( + addr = ALIGN(addr, huge_page_size(h)); + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + if (current->mm->get_unmapped_area == arch_get_unmapped_area) +--- a/arch/x86/kernel/sys_x86_64.c ++++ b/arch/x86/kernel/sys_x86_64.c +@@ -140,7 +140,7 @@ arch_get_unmapped_area(struct file *filp + addr = PAGE_ALIGN(addr); + vma = find_vma(mm, addr); + if (end - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + +@@ -183,7 +183,7 @@ arch_get_unmapped_area_topdown(struct fi + addr = PAGE_ALIGN(addr); + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + +--- a/arch/x86/mm/hugetlbpage.c ++++ b/arch/x86/mm/hugetlbpage.c +@@ -144,7 +144,7 @@ hugetlb_get_unmapped_area(struct file *f + addr = ALIGN(addr, huge_page_size(h)); + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + if (mm->get_unmapped_area == arch_get_unmapped_area) +--- a/arch/xtensa/kernel/syscall.c ++++ b/arch/xtensa/kernel/syscall.c +@@ -87,7 +87,7 @@ unsigned long arch_get_unmapped_area(str + /* At this point: (!vmm || addr < vmm->vm_end). */ + if (TASK_SIZE - len < addr) + return -ENOMEM; +- if (!vmm || addr + len <= vmm->vm_start) ++ if (!vmm || addr + len <= vm_start_gap(vmm)) + return addr; + addr = vmm->vm_end; + if (flags & MAP_SHARED) +--- a/fs/hugetlbfs/inode.c ++++ b/fs/hugetlbfs/inode.c +@@ -191,7 +191,7 @@ hugetlb_get_unmapped_area(struct file *f + addr = ALIGN(addr, huge_page_size(h)); + vma = find_vma(mm, addr); + if (TASK_SIZE - len >= addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma))) + return addr; + } + +--- a/fs/proc/task_mmu.c ++++ b/fs/proc/task_mmu.c +@@ -299,11 +299,7 @@ show_map_vma(struct seq_file *m, struct + + /* We don't show the stack guard page in /proc/maps */ + start = vma->vm_start; +- if (stack_guard_page_start(vma, start)) +- start += PAGE_SIZE; + end = vma->vm_end; +- if (stack_guard_page_end(vma, end)) +- end -= PAGE_SIZE; + + seq_setwidth(m, 25 + sizeof(void *) * 6 - 1); + seq_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu ", +--- a/include/linux/mm.h ++++ b/include/linux/mm.h +@@ -1356,39 +1356,11 @@ int clear_page_dirty_for_io(struct page + + int get_cmdline(struct task_struct *task, char *buffer, int buflen); + +-/* Is the vma a continuation of the stack vma above it? */ +-static inline int vma_growsdown(struct vm_area_struct *vma, unsigned long addr) +-{ +- return vma && (vma->vm_end == addr) && (vma->vm_flags & VM_GROWSDOWN); +-} +- + static inline bool vma_is_anonymous(struct vm_area_struct *vma) + { + return !vma->vm_ops; + } + +-static inline int stack_guard_page_start(struct vm_area_struct *vma, +- unsigned long addr) +-{ +- return (vma->vm_flags & VM_GROWSDOWN) && +- (vma->vm_start == addr) && +- !vma_growsdown(vma->vm_prev, addr); +-} +- +-/* Is the vma a continuation of the stack vma below it? */ +-static inline int vma_growsup(struct vm_area_struct *vma, unsigned long addr) +-{ +- return vma && (vma->vm_start == addr) && (vma->vm_flags & VM_GROWSUP); +-} +- +-static inline int stack_guard_page_end(struct vm_area_struct *vma, +- unsigned long addr) +-{ +- return (vma->vm_flags & VM_GROWSUP) && +- (vma->vm_end == addr) && +- !vma_growsup(vma->vm_next, addr); +-} +- + int vma_is_stack_for_current(struct vm_area_struct *vma); + + extern unsigned long move_page_tables(struct vm_area_struct *vma, +@@ -2127,6 +2099,7 @@ void page_cache_async_readahead(struct a + pgoff_t offset, + unsigned long size); + ++extern unsigned long stack_guard_gap; + /* Generic expand stack which grows the stack according to GROWS{UP,DOWN} */ + extern int expand_stack(struct vm_area_struct *vma, unsigned long address); + +@@ -2155,6 +2128,30 @@ static inline struct vm_area_struct * fi + return vma; + } + ++static inline unsigned long vm_start_gap(struct vm_area_struct *vma) ++{ ++ unsigned long vm_start = vma->vm_start; ++ ++ if (vma->vm_flags & VM_GROWSDOWN) { ++ vm_start -= stack_guard_gap; ++ if (vm_start > vma->vm_start) ++ vm_start = 0; ++ } ++ return vm_start; ++} ++ ++static inline unsigned long vm_end_gap(struct vm_area_struct *vma) ++{ ++ unsigned long vm_end = vma->vm_end; ++ ++ if (vma->vm_flags & VM_GROWSUP) { ++ vm_end += stack_guard_gap; ++ if (vm_end < vma->vm_end) ++ vm_end = -PAGE_SIZE; ++ } ++ return vm_end; ++} ++ + static inline unsigned long vma_pages(struct vm_area_struct *vma) + { + return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT; +--- a/mm/gup.c ++++ b/mm/gup.c +@@ -370,11 +370,6 @@ static int faultin_page(struct task_stru + /* mlock all present pages, but do not fault in new pages */ + if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK) + return -ENOENT; +- /* For mm_populate(), just skip the stack guard page. */ +- if ((*flags & FOLL_POPULATE) && +- (stack_guard_page_start(vma, address) || +- stack_guard_page_end(vma, address + PAGE_SIZE))) +- return -ENOENT; + if (*flags & FOLL_WRITE) + fault_flags |= FAULT_FLAG_WRITE; + if (*flags & FOLL_REMOTE) +--- a/mm/memory.c ++++ b/mm/memory.c +@@ -2699,40 +2699,6 @@ out_release: + } + + /* +- * This is like a special single-page "expand_{down|up}wards()", +- * except we must first make sure that 'address{-|+}PAGE_SIZE' +- * doesn't hit another vma. +- */ +-static inline int check_stack_guard_page(struct vm_area_struct *vma, unsigned long address) +-{ +- address &= PAGE_MASK; +- if ((vma->vm_flags & VM_GROWSDOWN) && address == vma->vm_start) { +- struct vm_area_struct *prev = vma->vm_prev; +- +- /* +- * Is there a mapping abutting this one below? +- * +- * That's only ok if it's the same stack mapping +- * that has gotten split.. +- */ +- if (prev && prev->vm_end == address) +- return prev->vm_flags & VM_GROWSDOWN ? 0 : -ENOMEM; +- +- return expand_downwards(vma, address - PAGE_SIZE); +- } +- if ((vma->vm_flags & VM_GROWSUP) && address + PAGE_SIZE == vma->vm_end) { +- struct vm_area_struct *next = vma->vm_next; +- +- /* As VM_GROWSDOWN but s/below/above/ */ +- if (next && next->vm_start == address + PAGE_SIZE) +- return next->vm_flags & VM_GROWSUP ? 0 : -ENOMEM; +- +- return expand_upwards(vma, address + PAGE_SIZE); +- } +- return 0; +-} +- +-/* + * We enter with non-exclusive mmap_sem (to exclude vma changes, + * but allow concurrent faults), and pte mapped but not yet locked. + * We return with mmap_sem still held, but pte unmapped and unlocked. +@@ -2748,10 +2714,6 @@ static int do_anonymous_page(struct faul + if (vma->vm_flags & VM_SHARED) + return VM_FAULT_SIGBUS; + +- /* Check if we need to add a guard page to the stack */ +- if (check_stack_guard_page(vma, fe->address) < 0) +- return VM_FAULT_SIGSEGV; +- + /* + * Use pte_alloc() instead of pte_alloc_map(). We can't run + * pte_offset_map() on pmds where a huge pmd might be created +--- a/mm/mmap.c ++++ b/mm/mmap.c +@@ -183,6 +183,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk) + unsigned long retval; + unsigned long newbrk, oldbrk; + struct mm_struct *mm = current->mm; ++ struct vm_area_struct *next; + unsigned long min_brk; + bool populate; + +@@ -228,7 +229,8 @@ SYSCALL_DEFINE1(brk, unsigned long, brk) + } + + /* Check against existing mmap mappings. */ +- if (find_vma_intersection(mm, oldbrk, newbrk+PAGE_SIZE)) ++ next = find_vma(mm, oldbrk); ++ if (next && newbrk + PAGE_SIZE > vm_start_gap(next)) + goto out; + + /* Ok, looks good - let it rip. */ +@@ -251,10 +253,22 @@ out: + + static long vma_compute_subtree_gap(struct vm_area_struct *vma) + { +- unsigned long max, subtree_gap; +- max = vma->vm_start; +- if (vma->vm_prev) +- max -= vma->vm_prev->vm_end; ++ unsigned long max, prev_end, subtree_gap; ++ ++ /* ++ * Note: in the rare case of a VM_GROWSDOWN above a VM_GROWSUP, we ++ * allow two stack_guard_gaps between them here, and when choosing ++ * an unmapped area; whereas when expanding we only require one. ++ * That's a little inconsistent, but keeps the code here simpler. ++ */ ++ max = vm_start_gap(vma); ++ if (vma->vm_prev) { ++ prev_end = vm_end_gap(vma->vm_prev); ++ if (max > prev_end) ++ max -= prev_end; ++ else ++ max = 0; ++ } + if (vma->vm_rb.rb_left) { + subtree_gap = rb_entry(vma->vm_rb.rb_left, + struct vm_area_struct, vm_rb)->rb_subtree_gap; +@@ -350,7 +364,7 @@ static void validate_mm(struct mm_struct + anon_vma_unlock_read(anon_vma); + } + +- highest_address = vma->vm_end; ++ highest_address = vm_end_gap(vma); + vma = vma->vm_next; + i++; + } +@@ -539,7 +553,7 @@ void __vma_link_rb(struct mm_struct *mm, + if (vma->vm_next) + vma_gap_update(vma->vm_next); + else +- mm->highest_vm_end = vma->vm_end; ++ mm->highest_vm_end = vm_end_gap(vma); + + /* + * vma->vm_prev wasn't known when we followed the rbtree to find the +@@ -854,7 +868,7 @@ again: + vma_gap_update(vma); + if (end_changed) { + if (!next) +- mm->highest_vm_end = end; ++ mm->highest_vm_end = vm_end_gap(vma); + else if (!adjust_next) + vma_gap_update(next); + } +@@ -939,7 +953,7 @@ again: + * mm->highest_vm_end doesn't need any update + * in remove_next == 1 case. + */ +- VM_WARN_ON(mm->highest_vm_end != end); ++ VM_WARN_ON(mm->highest_vm_end != vm_end_gap(vma)); + } + } + if (insert && file) +@@ -1783,7 +1797,7 @@ unsigned long unmapped_area(struct vm_un + + while (true) { + /* Visit left subtree if it looks promising */ +- gap_end = vma->vm_start; ++ gap_end = vm_start_gap(vma); + if (gap_end >= low_limit && vma->vm_rb.rb_left) { + struct vm_area_struct *left = + rb_entry(vma->vm_rb.rb_left, +@@ -1794,7 +1808,7 @@ unsigned long unmapped_area(struct vm_un + } + } + +- gap_start = vma->vm_prev ? vma->vm_prev->vm_end : 0; ++ gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0; + check_current: + /* Check if current node has a suitable gap */ + if (gap_start > high_limit) +@@ -1821,8 +1835,8 @@ check_current: + vma = rb_entry(rb_parent(prev), + struct vm_area_struct, vm_rb); + if (prev == vma->vm_rb.rb_left) { +- gap_start = vma->vm_prev->vm_end; +- gap_end = vma->vm_start; ++ gap_start = vm_end_gap(vma->vm_prev); ++ gap_end = vm_start_gap(vma); + goto check_current; + } + } +@@ -1886,7 +1900,7 @@ unsigned long unmapped_area_topdown(stru + + while (true) { + /* Visit right subtree if it looks promising */ +- gap_start = vma->vm_prev ? vma->vm_prev->vm_end : 0; ++ gap_start = vma->vm_prev ? vm_end_gap(vma->vm_prev) : 0; + if (gap_start <= high_limit && vma->vm_rb.rb_right) { + struct vm_area_struct *right = + rb_entry(vma->vm_rb.rb_right, +@@ -1899,7 +1913,7 @@ unsigned long unmapped_area_topdown(stru + + check_current: + /* Check if current node has a suitable gap */ +- gap_end = vma->vm_start; ++ gap_end = vm_start_gap(vma); + if (gap_end < low_limit) + return -ENOMEM; + if (gap_start <= high_limit && gap_end - gap_start >= length) +@@ -1925,7 +1939,7 @@ check_current: + struct vm_area_struct, vm_rb); + if (prev == vma->vm_rb.rb_right) { + gap_start = vma->vm_prev ? +- vma->vm_prev->vm_end : 0; ++ vm_end_gap(vma->vm_prev) : 0; + goto check_current; + } + } +@@ -1963,7 +1977,7 @@ arch_get_unmapped_area(struct file *filp + unsigned long len, unsigned long pgoff, unsigned long flags) + { + struct mm_struct *mm = current->mm; +- struct vm_area_struct *vma; ++ struct vm_area_struct *vma, *prev; + struct vm_unmapped_area_info info; + + if (len > TASK_SIZE - mmap_min_addr) +@@ -1974,9 +1988,10 @@ arch_get_unmapped_area(struct file *filp + + if (addr) { + addr = PAGE_ALIGN(addr); +- vma = find_vma(mm, addr); ++ vma = find_vma_prev(mm, addr, &prev); + if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma)) && ++ (!prev || addr >= vm_end_gap(prev))) + return addr; + } + +@@ -1999,7 +2014,7 @@ arch_get_unmapped_area_topdown(struct fi + const unsigned long len, const unsigned long pgoff, + const unsigned long flags) + { +- struct vm_area_struct *vma; ++ struct vm_area_struct *vma, *prev; + struct mm_struct *mm = current->mm; + unsigned long addr = addr0; + struct vm_unmapped_area_info info; +@@ -2014,9 +2029,10 @@ arch_get_unmapped_area_topdown(struct fi + /* requesting a specific address */ + if (addr) { + addr = PAGE_ALIGN(addr); +- vma = find_vma(mm, addr); ++ vma = find_vma_prev(mm, addr, &prev); + if (TASK_SIZE - len >= addr && addr >= mmap_min_addr && +- (!vma || addr + len <= vma->vm_start)) ++ (!vma || addr + len <= vm_start_gap(vma)) && ++ (!prev || addr >= vm_end_gap(prev))) + return addr; + } + +@@ -2151,21 +2167,19 @@ find_vma_prev(struct mm_struct *mm, unsi + * update accounting. This is shared with both the + * grow-up and grow-down cases. + */ +-static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, unsigned long grow) ++static int acct_stack_growth(struct vm_area_struct *vma, ++ unsigned long size, unsigned long grow) + { + struct mm_struct *mm = vma->vm_mm; + struct rlimit *rlim = current->signal->rlim; +- unsigned long new_start, actual_size; ++ unsigned long new_start; + + /* address space limit tests */ + if (!may_expand_vm(mm, vma->vm_flags, grow)) + return -ENOMEM; + + /* Stack limit test */ +- actual_size = size; +- if (size && (vma->vm_flags & (VM_GROWSUP | VM_GROWSDOWN))) +- actual_size -= PAGE_SIZE; +- if (actual_size > READ_ONCE(rlim[RLIMIT_STACK].rlim_cur)) ++ if (size > READ_ONCE(rlim[RLIMIT_STACK].rlim_cur)) + return -ENOMEM; + + /* mlock limit tests */ +@@ -2203,17 +2217,30 @@ static int acct_stack_growth(struct vm_a + int expand_upwards(struct vm_area_struct *vma, unsigned long address) + { + struct mm_struct *mm = vma->vm_mm; ++ struct vm_area_struct *next; ++ unsigned long gap_addr; + int error = 0; + + if (!(vma->vm_flags & VM_GROWSUP)) + return -EFAULT; + + /* Guard against wrapping around to address 0. */ +- if (address < PAGE_ALIGN(address+4)) +- address = PAGE_ALIGN(address+4); +- else ++ address &= PAGE_MASK; ++ address += PAGE_SIZE; ++ if (!address) + return -ENOMEM; + ++ /* Enforce stack_guard_gap */ ++ gap_addr = address + stack_guard_gap; ++ if (gap_addr < address) ++ return -ENOMEM; ++ next = vma->vm_next; ++ if (next && next->vm_start < gap_addr) { ++ if (!(next->vm_flags & VM_GROWSUP)) ++ return -ENOMEM; ++ /* Check that both stack segments have the same anon_vma? */ ++ } ++ + /* We must make sure the anon_vma is allocated. */ + if (unlikely(anon_vma_prepare(vma))) + return -ENOMEM; +@@ -2257,7 +2284,7 @@ int expand_upwards(struct vm_area_struct + if (vma->vm_next) + vma_gap_update(vma->vm_next); + else +- mm->highest_vm_end = address; ++ mm->highest_vm_end = vm_end_gap(vma); + spin_unlock(&mm->page_table_lock); + + perf_event_mmap(vma); +@@ -2278,6 +2305,8 @@ int expand_downwards(struct vm_area_stru + unsigned long address) + { + struct mm_struct *mm = vma->vm_mm; ++ struct vm_area_struct *prev; ++ unsigned long gap_addr; + int error; + + address &= PAGE_MASK; +@@ -2285,6 +2314,17 @@ int expand_downwards(struct vm_area_stru + if (error) + return error; + ++ /* Enforce stack_guard_gap */ ++ gap_addr = address - stack_guard_gap; ++ if (gap_addr > address) ++ return -ENOMEM; ++ prev = vma->vm_prev; ++ if (prev && prev->vm_end > gap_addr) { ++ if (!(prev->vm_flags & VM_GROWSDOWN)) ++ return -ENOMEM; ++ /* Check that both stack segments have the same anon_vma? */ ++ } ++ + /* We must make sure the anon_vma is allocated. */ + if (unlikely(anon_vma_prepare(vma))) + return -ENOMEM; +@@ -2339,28 +2379,25 @@ int expand_downwards(struct vm_area_stru + return error; + } + +-/* +- * Note how expand_stack() refuses to expand the stack all the way to +- * abut the next virtual mapping, *unless* that mapping itself is also +- * a stack mapping. We want to leave room for a guard page, after all +- * (the guard page itself is not added here, that is done by the +- * actual page faulting logic) +- * +- * This matches the behavior of the guard page logic (see mm/memory.c: +- * check_stack_guard_page()), which only allows the guard page to be +- * removed under these circumstances. +- */ ++/* enforced gap between the expanding stack and other mappings. */ ++unsigned long stack_guard_gap = 256UL<<PAGE_SHIFT; ++ ++static int __init cmdline_parse_stack_guard_gap(char *p) ++{ ++ unsigned long val; ++ char *endptr; ++ ++ val = simple_strtoul(p, &endptr, 10); ++ if (!*endptr) ++ stack_guard_gap = val << PAGE_SHIFT; ++ ++ return 0; ++} ++__setup("stack_guard_gap=", cmdline_parse_stack_guard_gap); ++ + #ifdef CONFIG_STACK_GROWSUP + int expand_stack(struct vm_area_struct *vma, unsigned long address) + { +- struct vm_area_struct *next; +- +- address &= PAGE_MASK; +- next = vma->vm_next; +- if (next && next->vm_start == address + PAGE_SIZE) { +- if (!(next->vm_flags & VM_GROWSUP)) +- return -ENOMEM; +- } + return expand_upwards(vma, address); + } + +@@ -2382,14 +2419,6 @@ find_extend_vma(struct mm_struct *mm, un + #else + int expand_stack(struct vm_area_struct *vma, unsigned long address) + { +- struct vm_area_struct *prev; +- +- address &= PAGE_MASK; +- prev = vma->vm_prev; +- if (prev && prev->vm_end == address) { +- if (!(prev->vm_flags & VM_GROWSDOWN)) +- return -ENOMEM; +- } + return expand_downwards(vma, address); + } + +@@ -2487,7 +2516,7 @@ detach_vmas_to_be_unmapped(struct mm_str + vma->vm_prev = prev; + vma_gap_update(vma); + } else +- mm->highest_vm_end = prev ? prev->vm_end : 0; ++ mm->highest_vm_end = prev ? vm_end_gap(prev) : 0; + tail_vma->vm_next = NULL; + + /* Kill the cache */ |