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-rw-r--r--meta-rcar-gen2/recipes-kernel/linux/linux-renesas/0001-SEC-Backport-mm-larger-stack-guard-gap-between-vmas.patch797
1 files changed, 797 insertions, 0 deletions
diff --git a/meta-rcar-gen2/recipes-kernel/linux/linux-renesas/0001-SEC-Backport-mm-larger-stack-guard-gap-between-vmas.patch b/meta-rcar-gen2/recipes-kernel/linux/linux-renesas/0001-SEC-Backport-mm-larger-stack-guard-gap-between-vmas.patch
new file mode 100644
index 0000000..002e9f1
--- /dev/null
+++ b/meta-rcar-gen2/recipes-kernel/linux/linux-renesas/0001-SEC-Backport-mm-larger-stack-guard-gap-between-vmas.patch
@@ -0,0 +1,797 @@
+From 0558b5c626426017848d9f3b7af380494c3deece Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Jan-Simon=20M=C3=B6ller?= <jsmoeller@linuxfoundation.org>
+Date: Tue, 27 Jun 2017 22:46:11 +0200
+Subject: [PATCH 1/3] [SEC][Backport] mm: larger stack guard gap, between vmas
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+This change backports
+https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/patch/?id=1ad9a25dd06fda9bdc27875e1cedb8277accb212
+
+Signed-off-by: Jan-Simon Möller <jsmoeller@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/powerpc/mm/slice.c | 2 +-
+ 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/memory.c | 49 -----------
+ mm/mmap.c | 168 ++++++++++++++++++++----------------
+ 18 files changed, 144 insertions(+), 171 deletions(-)
+
+diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
+index 9859ddf..09924a9 100644
+--- a/Documentation/kernel-parameters.txt
++++ b/Documentation/kernel-parameters.txt
+@@ -2884,6 +2884,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
+ 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.
+
+diff --git a/arch/arc/mm/mmap.c b/arch/arc/mm/mmap.c
+index 2e06d56..cf4ae69 100644
+--- a/arch/arc/mm/mmap.c
++++ b/arch/arc/mm/mmap.c
+@@ -64,7 +64,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long 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;
+ }
+
+diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
+index 5ef506c..984509e 100644
+--- a/arch/arm/mm/mmap.c
++++ b/arch/arm/mm/mmap.c
+@@ -89,7 +89,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long 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;
+ }
+
+@@ -140,7 +140,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+ 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;
+ }
+
+diff --git a/arch/frv/mm/elf-fdpic.c b/arch/frv/mm/elf-fdpic.c
+index 836f147..efa59f1 100644
+--- a/arch/frv/mm/elf-fdpic.c
++++ b/arch/frv/mm/elf-fdpic.c
+@@ -74,7 +74,7 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, unsi
+ 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;
+ }
+
+diff --git a/arch/mips/mm/mmap.c b/arch/mips/mm/mmap.c
+index 7e5fe27..0bb4295 100644
+--- a/arch/mips/mm/mmap.c
++++ b/arch/mips/mm/mmap.c
+@@ -92,7 +92,7 @@ static unsigned long arch_get_unmapped_area_common(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;
+ }
+
+diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
+index 7ce9cf3..887365a 100644
+--- a/arch/powerpc/mm/slice.c
++++ b/arch/powerpc/mm/slice.c
+@@ -103,7 +103,7 @@ static int slice_area_is_free(struct mm_struct *mm, unsigned long addr,
+ 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)
+diff --git a/arch/sh/mm/mmap.c b/arch/sh/mm/mmap.c
+index 6777177..7df7d59 100644
+--- a/arch/sh/mm/mmap.c
++++ b/arch/sh/mm/mmap.c
+@@ -63,7 +63,7 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long 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;
+ }
+
+@@ -113,7 +113,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+
+ 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;
+ }
+
+diff --git a/arch/sparc/kernel/sys_sparc_64.c b/arch/sparc/kernel/sys_sparc_64.c
+index 2daaaa6..79b981e 100644
+--- a/arch/sparc/kernel/sys_sparc_64.c
++++ b/arch/sparc/kernel/sys_sparc_64.c
+@@ -119,7 +119,7 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr, unsi
+
+ 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;
+ }
+
+@@ -182,7 +182,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+
+ 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;
+ }
+
+diff --git a/arch/sparc/mm/hugetlbpage.c b/arch/sparc/mm/hugetlbpage.c
+index d2b5944..ce49370 100644
+--- a/arch/sparc/mm/hugetlbpage.c
++++ b/arch/sparc/mm/hugetlbpage.c
+@@ -118,7 +118,7 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
+ 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)
+diff --git a/arch/tile/mm/hugetlbpage.c b/arch/tile/mm/hugetlbpage.c
+index 650ccff..c75eac7 100644
+--- a/arch/tile/mm/hugetlbpage.c
++++ b/arch/tile/mm/hugetlbpage.c
+@@ -297,7 +297,7 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
+ 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)
+diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c
+index 30277e2..d050393 100644
+--- a/arch/x86/kernel/sys_x86_64.c
++++ b/arch/x86/kernel/sys_x86_64.c
+@@ -127,7 +127,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ 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;
+ }
+
+@@ -166,7 +166,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+ 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;
+ }
+
+diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
+index ae1aa71..6adf3d9 100644
+--- a/arch/x86/mm/hugetlbpage.c
++++ b/arch/x86/mm/hugetlbpage.c
+@@ -341,7 +341,7 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
+ 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)
+diff --git a/arch/xtensa/kernel/syscall.c b/arch/xtensa/kernel/syscall.c
+index 5d3f7a1..1ff0b92 100644
+--- a/arch/xtensa/kernel/syscall.c
++++ b/arch/xtensa/kernel/syscall.c
+@@ -86,7 +86,7 @@ unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ /* 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)
+diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
+index 4e5f332..db7d89c 100644
+--- a/fs/hugetlbfs/inode.c
++++ b/fs/hugetlbfs/inode.c
+@@ -169,7 +169,7 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
+ 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;
+ }
+
+diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
+index 65fc60a..a5884ed 100644
+--- a/fs/proc/task_mmu.c
++++ b/fs/proc/task_mmu.c
+@@ -279,11 +279,7 @@ show_map_vma(struct seq_file *m, struct vm_area_struct *vma, int is_pid)
+
+ /* 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_printf(m, "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu %n",
+ start,
+diff --git a/include/linux/mm.h b/include/linux/mm.h
+index 263b405..294a6b1 100644
+--- a/include/linux/mm.h
++++ b/include/linux/mm.h
+@@ -1056,34 +1056,6 @@ int set_page_dirty(struct page *page);
+ int set_page_dirty_lock(struct page *page);
+ int clear_page_dirty_for_io(struct page *page);
+
+-/* 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 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);
+-}
+-
+ extern pid_t
+ vm_is_stack(struct task_struct *task, struct vm_area_struct *vma, int in_group);
+
+@@ -1609,6 +1581,7 @@ unsigned long ra_submit(struct file_ra_state *ra,
+ struct address_space *mapping,
+ struct file *filp);
+
++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);
+
+@@ -1637,6 +1610,30 @@ static inline struct vm_area_struct * find_vma_intersection(struct mm_struct * m
+ 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;
+diff --git a/mm/memory.c b/mm/memory.c
+index 3a3f316..06bbba9 100644
+--- a/mm/memory.c
++++ b/mm/memory.c
+@@ -1654,12 +1654,6 @@ no_page_table:
+ return page;
+ }
+
+-static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
+-{
+- return stack_guard_page_start(vma, addr) ||
+- stack_guard_page_end(vma, addr+PAGE_SIZE);
+-}
+-
+ /**
+ * __get_user_pages() - pin user pages in memory
+ * @tsk: task_struct of target task
+@@ -1827,11 +1821,6 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
+ int ret;
+ unsigned int fault_flags = 0;
+
+- /* For mlock, just skip the stack guard page. */
+- if (foll_flags & FOLL_MLOCK) {
+- if (stack_guard_page(vma, start))
+- goto next_page;
+- }
+ if (foll_flags & FOLL_WRITE)
+ fault_flags |= FAULT_FLAG_WRITE;
+ if (nonblocking)
+@@ -3186,40 +3175,6 @@ 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;
+-
+- 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;
+-
+- 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.
+@@ -3234,10 +3189,6 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
+
+ pte_unmap(page_table);
+
+- /* Check if we need to add a guard page to the stack */
+- if (check_stack_guard_page(vma, address) < 0)
+- return VM_FAULT_SIGBUS;
+-
+ /* Use the zero-page for reads */
+ if (!(flags & FAULT_FLAG_WRITE)) {
+ entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
+diff --git a/mm/mmap.c b/mm/mmap.c
+index 8f87b14..cbdac38 100644
+--- a/mm/mmap.c
++++ b/mm/mmap.c
+@@ -263,6 +263,7 @@ SYSCALL_DEFINE1(brk, unsigned long, brk)
+ unsigned long rlim, retval;
+ unsigned long newbrk, oldbrk;
+ struct mm_struct *mm = current->mm;
++ struct vm_area_struct *next;
+ unsigned long min_brk;
+ bool populate;
+
+@@ -308,7 +309,8 @@ 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. */
+@@ -331,10 +333,22 @@ 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;
+@@ -418,7 +432,7 @@ void validate_mm(struct mm_struct *mm)
+ list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
+ anon_vma_interval_tree_verify(avc);
+ vma_unlock_anon_vma(vma);
+- highest_address = vma->vm_end;
++ highest_address = vm_end_gap(vma);
+ vma = vma->vm_next;
+ i++;
+ }
+@@ -586,7 +600,7 @@ void __vma_link_rb(struct mm_struct *mm, struct vm_area_struct *vma,
+ 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
+@@ -835,7 +849,7 @@ again: remove_next = 1 + (end > next->vm_end);
+ 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);
+ }
+@@ -878,7 +892,7 @@ again: remove_next = 1 + (end > next->vm_end);
+ else if (next)
+ vma_gap_update(next);
+ else
+- mm->highest_vm_end = end;
++ WARN_ON(mm->highest_vm_end != vm_end_gap(vma));
+ }
+ if (insert && file)
+ uprobe_mmap(insert);
+@@ -1670,7 +1684,7 @@ unsigned long unmapped_area(struct vm_unmapped_area_info *info)
+
+ 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,
+@@ -1681,7 +1695,7 @@ unsigned long unmapped_area(struct vm_unmapped_area_info *info)
+ }
+ }
+
+- 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)
+@@ -1708,8 +1722,8 @@ 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;
+ }
+ }
+@@ -1773,7 +1787,7 @@ unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
+
+ 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,
+@@ -1786,7 +1800,7 @@ unsigned long unmapped_area_topdown(struct vm_unmapped_area_info *info)
+
+ 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)
+@@ -1812,7 +1826,7 @@ 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;
+ }
+ }
+@@ -1850,7 +1864,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
+ 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)
+@@ -1861,9 +1875,10 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
+
+ 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;
+ }
+
+@@ -1895,7 +1910,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+ 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;
+@@ -1910,9 +1925,10 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
+ /* 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;
+ }
+
+@@ -2104,32 +2120,40 @@ static int acct_stack_growth(struct vm_area_struct *vma, unsigned long size, uns
+ */
+ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
+ {
+- int error;
++ struct vm_area_struct *next;
++ unsigned long gap_addr;
++ int error = 0;
+
+ if (!(vma->vm_flags & VM_GROWSUP))
+ return -EFAULT;
+
+- /*
+- * We must make sure the anon_vma is allocated
+- * so that the anon_vma locking is not a noop.
+- */
++ /* Guard against wrapping around to address 0. */
++ 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;
+- vma_lock_anon_vma(vma);
+
+ /*
+ * vma->vm_start/vm_end cannot change under us because the caller
+ * is required to hold the mmap_sem in read mode. We need the
+ * anon_vma lock to serialize against concurrent expand_stacks.
+- * Also guard against wrapping around to address 0.
+ */
+- if (address < PAGE_ALIGN(address+4))
+- address = PAGE_ALIGN(address+4);
+- else {
+- vma_unlock_anon_vma(vma);
+- return -ENOMEM;
+- }
+- error = 0;
++ vma_lock_anon_vma(vma);
+
+ /* Somebody else might have raced and expanded it already */
+ if (address > vma->vm_end) {
+@@ -2160,7 +2184,7 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
+ if (vma->vm_next)
+ vma_gap_update(vma->vm_next);
+ else
+- vma->vm_mm->highest_vm_end = address;
++ vma->vm_mm->highest_vm_end = vm_end_gap(vma);
+ spin_unlock(&vma->vm_mm->page_table_lock);
+
+ perf_event_mmap(vma);
+@@ -2180,27 +2204,36 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address)
+ int expand_downwards(struct vm_area_struct *vma,
+ unsigned long address)
+ {
++ struct vm_area_struct *prev;
++ unsigned long gap_addr;
+ int error;
+
+- /*
+- * We must make sure the anon_vma is allocated
+- * so that the anon_vma locking is not a noop.
+- */
+- if (unlikely(anon_vma_prepare(vma)))
+- return -ENOMEM;
+-
+ address &= PAGE_MASK;
+ error = security_mmap_addr(address);
+ if (error)
+ return error;
+
+- vma_lock_anon_vma(vma);
++ /* 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;
+
+ /*
+ * vma->vm_start/vm_end cannot change under us because the caller
+ * is required to hold the mmap_sem in read mode. We need the
+ * anon_vma lock to serialize against concurrent expand_stacks.
+ */
++ vma_lock_anon_vma(vma);
+
+ /* Somebody else might have raced and expanded it already */
+ if (address < vma->vm_start) {
+@@ -2242,28 +2275,25 @@ int expand_downwards(struct vm_area_struct *vma,
+ 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);
+ }
+
+@@ -2285,14 +2315,6 @@ find_extend_vma(struct mm_struct *mm, unsigned long addr)
+ #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);
+ }
+
+@@ -2389,7 +2411,7 @@ detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma,
+ 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;
+ if (mm->unmap_area == arch_unmap_area)
+ addr = prev ? prev->vm_end : mm->mmap_base;
+--
+2.1.4
+