Re: [PATCH] mm: larger stack guard gap, between vmas

Hugh Dickins
2017-06-24T09:11:47Z

On Thu, 22 Jun 2017, Hugh Dickins wrote:
> On Thu, 22 Jun 2017, Ben Hutchings wrote:
>
> > Here's my attempt at a backport to 3.2. This is only tested on
> > x86_64 and I think I should introduce local variables for
> > vma_start_gap() in a few places. I had to cherry-pick commit
> > 09884964335e "mm: do not grow the stack vma just because of an overrun
> > on preceding vma" before this one (which was a clean cherry-pick).
>
> Both your speed and your stamina are much better than mine; and your
> patch belies your Sturgeon's law signature. I haven't got beyond the
> architectures yet in my parallel attempt, and you do appear to be
> doing everything right (but a local variable often welcome, yes).
>
> I'm giving up for the night, will contine tomorrow.
> The only discrepancy I notice so far is that I have
> arch/alpha/kernel/osf_sys.c
> arch/ia64/mm/hugetlbpage.c
> arch/sparc/kernel/sys_sparc_32.c
> in my list of changed files, but they're not in yours.

And here's my attempt at a backport to 3.2.89, at last.
I know it builds and boots and runs on x86 64 and 32,
but that's about all that I've tried.

If you diff against yours (I preferred not to send that diff,
because of the couple of rejects in yours against 3.2.89),
you'll find most of the difference is just noise from where
I used a variable, but you had not yet done so in yours.

But there are those three missing files, and there are a few
places where I have a little "if (prev) {" block at the head of
the loop after find_vma_prev(): I think those loops start off
wrongly without that.

I notice now that you don't use find_vma_prev() in your generic
(mm/mmap.c) arch_get_unmapped_area() and _topdown(): and now
that I reflect on it, I think you're perfectly correct to keep
those simple (especially given the inefficient implementation
of find_vma_prev() in 3.2 - only later was it changed to make
use of vm_prev), since both ia64 and parisc provide their own
arch_get_unmapped_area() in this release, and neither use the
_topdown().

Whereas I spent much too much time on adapting those generics
to vm_end_gap(), and pretty much gave up on the _topdown() -
it grieved me to end up calling find_vma_prev() each time
around the loop (where before it called find_vma() each time
around the loop), there is definitely better use to be made
of vm_prev there, but too hard to get right as I grew tired.

So please at least take a look through the diff from yours, I
think you'll find a few things to bring in, but a lot to ignore.

Hugh

diff -purN 302s/arch/alpha/kernel/osf_sys.c 302h/arch/alpha/kernel/osf_sys.c
--- 302s/arch/alpha/kernel/osf_sys.c 2011-10-24 00:10:05.000000000 -0700
+++ 302h/arch/alpha/kernel/osf_sys.c 2017-06-22 18:16:22.425283525 -0700
@@ -1147,7 +1147,7 @@ arch_get_unmapped_area_1(unsigned long a
/* At this point: (!vma || addr < vma->vm_end). */
if (limit - len < addr)
return -ENOMEM;
- if (!vma || addr + len <= vma->vm_start)
+ if (!vma || addr + len <= vm_start_vma(vma))
return addr;
addr = vma->vm_end;
vma = vma->vm_next;
diff -purN 302s/arch/arm/mm/mmap.c 302h/arch/arm/mm/mmap.c
--- 302s/arch/arm/mm/mmap.c 2012-01-04 15:55:44.000000000 -0800
+++ 302h/arch/arm/mm/mmap.c 2017-06-23 21:30:38.061880299 -0700
@@ -30,7 +30,7 @@ arch_get_unmapped_area(struct file *filp
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
- unsigned long start_addr;
+ unsigned long start_addr, vm_start;
int do_align = 0;
int aliasing = cache_is_vipt_aliasing();

@@ -62,7 +62,7 @@ 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;
}
if (len > mm->cached_hole_size) {
@@ -96,15 +96,17 @@ full_search:
}
return -ENOMEM;
}
- if (!vma || addr + len <= vma->vm_start) {
+ if (vma)
+ vm_start = vm_start_gap(vma);
+ if (!vma || addr + len <= vm_start) {
/*
* Remember the place where we stopped the search:
*/
mm->free_area_cache = addr + len;
return addr;
}
- if (addr + mm->cached_hole_size < vma->vm_start)
- mm->cached_hole_size = vma->vm_start - addr;
+ if (addr + mm->cached_hole_size < vm_start)
+ mm->cached_hole_size = vm_start - addr;
addr = vma->vm_end;
if (do_align)
addr = COLOUR_ALIGN(addr, pgoff);
diff -purN 302s/arch/frv/mm/elf-fdpic.c 302h/arch/frv/mm/elf-fdpic.c
--- 302s/arch/frv/mm/elf-fdpic.c 2007-07-08 16:32:17.000000000 -0700
+++ 302h/arch/frv/mm/elf-fdpic.c 2017-06-22 18:27:22.823308633 -0700
@@ -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;
}

@@ -89,7 +89,7 @@ unsigned long arch_get_unmapped_area(str
for (; vma; vma = vma->vm_next) {
if (addr > limit)
break;
- if (addr + len <= vma->vm_start)
+ if (addr + len <= vm_start_gap(vma))
goto success;
addr = vma->vm_end;
}
@@ -104,7 +104,7 @@ unsigned long arch_get_unmapped_area(str
for (; vma; vma = vma->vm_next) {
if (addr > limit)
break;
- if (addr + len <= vma->vm_start)
+ if (addr + len <= vm_start_gap(vma))
goto success;
addr = vma->vm_end;
}
diff -purN 302s/arch/ia64/kernel/sys_ia64.c 302h/arch/ia64/kernel/sys_ia64.c
--- 302s/arch/ia64/kernel/sys_ia64.c 2010-02-24 10:52:17.000000000 -0800
+++ 302h/arch/ia64/kernel/sys_ia64.c 2017-06-23 21:31:37.581321626 -0700
@@ -27,7 +27,8 @@ arch_get_unmapped_area (struct file *fil
long map_shared = (flags & MAP_SHARED);
unsigned long start_addr, align_mask = PAGE_SIZE - 1;
struct mm_struct *mm = current->mm;
- struct vm_area_struct *vma;
+ struct vm_area_struct *vma, *prev;
+ unsigned long prev_end;

if (len > RGN_MAP_LIMIT)
return -ENOMEM;
@@ -58,7 +59,17 @@ arch_get_unmapped_area (struct file *fil
full_search:
start_addr = addr = (addr + align_mask) & ~align_mask;

- for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
+ for (vma = find_vma_prev(mm, addr, &prev); ; prev = vma,
+ vma = vma->vm_next) {
+ if (prev) {
+ prev_end = vm_end_gap(prev);
+ if (addr < prev_end) {
+ addr = (prev_end + align_mask) & ~align_mask;
+ /* If vma already violates gap, forget it */
+ if (vma && addr > vma->vm_start)
+ addr = vma->vm_start;
+ }
+ }
/* At this point: (!vma || addr < vma->vm_end). */
if (TASK_SIZE - len < addr || RGN_MAP_LIMIT - len < REGION_OFFSET(addr)) {
if (start_addr != TASK_UNMAPPED_BASE) {
@@ -68,12 +79,11 @@ arch_get_unmapped_area (struct file *fil
}
return -ENOMEM;
}
- if (!vma || addr + len <= vma->vm_start) {
+ if (!vma || addr + len <= vm_start_gap(vma)) {
/* Remember the address where we stopped this search: */
mm->free_area_cache = addr + len;
return addr;
}
- addr = (vma->vm_end + align_mask) & ~align_mask;
}
}

diff -purN 302s/arch/ia64/mm/hugetlbpage.c 302h/arch/ia64/mm/hugetlbpage.c
--- 302s/arch/ia64/mm/hugetlbpage.c 2011-03-14 18:20:32.000000000 -0700
+++ 302h/arch/ia64/mm/hugetlbpage.c 2017-06-22 20:50:22.569517894 -0700
@@ -171,9 +171,9 @@ unsigned long hugetlb_get_unmapped_area(
/* At this point: (!vmm || addr < vmm->vm_end). */
if (REGION_OFFSET(addr) + len > RGN_MAP_LIMIT)
return -ENOMEM;
- if (!vmm || (addr + len) <= vmm->vm_start)
+ if (!vmm || (addr + len) <= vm_start_gap(vmm))
return addr;
- addr = ALIGN(vmm->vm_end, HPAGE_SIZE);
+ addr = ALIGN(vm_end_gap(vmm), HPAGE_SIZE);
}
}

diff -purN 302s/arch/mips/mm/mmap.c 302h/arch/mips/mm/mmap.c
--- 302s/arch/mips/mm/mmap.c 2011-10-24 00:10:05.000000000 -0700
+++ 302h/arch/mips/mm/mmap.c 2017-06-22 20:34:16.758377572 -0700
@@ -70,6 +70,7 @@ static unsigned long arch_get_unmapped_a
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
unsigned long addr = addr0;
+ unsigned long vm_start;
int do_color_align;

if (unlikely(len > TASK_SIZE))
@@ -103,7 +104,7 @@ 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;
}

@@ -118,7 +119,7 @@ static unsigned long arch_get_unmapped_a
/* At this point: (!vma || addr < vma->vm_end). */
if (TASK_SIZE - len < addr)
return -ENOMEM;
- if (!vma || addr + len <= vma->vm_start)
+ if (!vma || addr + len <= vm_start_gap(vma))
return addr;
addr = vma->vm_end;
if (do_color_align)
@@ -145,7 +146,7 @@ static unsigned long arch_get_unmapped_a
/* make sure it can fit in the remaining address space */
if (likely(addr > len)) {
vma = find_vma(mm, addr - len);
- if (!vma || addr <= vma->vm_start) {
+ if (!vma || addr <= vm_start_gap(vma)) {
/* cache the address as a hint for next time */
return mm->free_area_cache = addr - len;
}
@@ -165,20 +166,22 @@ static unsigned long arch_get_unmapped_a
* return with success:
*/
vma = find_vma(mm, addr);
- if (likely(!vma || addr + len <= vma->vm_start)) {
+ if (vma)
+ vm_start = vm_start_gap(vma);
+ if (likely(!vma || addr + len <= vm_start)) {
/* cache the address as a hint for next time */
return mm->free_area_cache = addr;
}

/* remember the largest hole we saw so far */
- if (addr + mm->cached_hole_size < vma->vm_start)
- mm->cached_hole_size = vma->vm_start - addr;
+ if (addr + mm->cached_hole_size < vm_start)
+ mm->cached_hole_size = vm_start - addr;

/* try just below the current vma->vm_start */
- addr = vma->vm_start - len;
+ addr = vm_start - len;
if (do_color_align)
addr = COLOUR_ALIGN_DOWN(addr, pgoff);
- } while (likely(len < vma->vm_start));
+ } while (likely(len < vm_start));

bottomup:
/*
diff -purN 302s/arch/parisc/kernel/sys_parisc.c 302h/arch/parisc/kernel/sys_parisc.c
--- 302s/arch/parisc/kernel/sys_parisc.c 2017-06-20 16:22:15.561319552 -0700
+++ 302h/arch/parisc/kernel/sys_parisc.c 2017-06-23 21:35:09.003338157 -0700
@@ -35,17 +35,27 @@

static unsigned long get_unshared_area(unsigned long addr, unsigned long len)
{
- struct vm_area_struct *vma;
+ struct vm_area_struct *vma, *prev;
+ unsigned long prev_end;

addr = PAGE_ALIGN(addr);

- for (vma = find_vma(current->mm, addr); ; vma = vma->vm_next) {
+ for (vma = find_vma_prev(current->mm, addr, &prev); ; prev = vma,
+ vma = vma->vm_next) {
+ if (prev) {
+ prev_end = vm_end_gap(prev);
+ if (addr < prev_end) {
+ addr = prev_end;
+ /* If vma already violates gap, forget it */
+ if (vma && addr > vma->vm_start)
+ addr = vma->vm_start;
+ }
+ }
/* At this point: (!vma || addr < vma->vm_end). */
if (TASK_SIZE - len < addr)
return -ENOMEM;
- if (!vma || addr + len <= vma->vm_start)
+ if (!vma || addr + len <= vm_start_gap(vma))
return addr;
- addr = vma->vm_end;
}
}

@@ -70,22 +80,32 @@ static int get_offset(struct address_spa
static unsigned long get_shared_area(struct address_space *mapping,
unsigned long addr, unsigned long len, unsigned long pgoff)
{
- struct vm_area_struct *vma;
+ struct vm_area_struct *vma, *prev;
+ unsigned long prev_end;
int offset = mapping ? get_offset(mapping) : 0;

offset = (offset + (pgoff << PAGE_SHIFT)) & 0x3FF000;

addr = DCACHE_ALIGN(addr - offset) + offset;

- for (vma = find_vma(current->mm, addr); ; vma = vma->vm_next) {
+ for (vma = find_vma_prev(current->mm, addr, &prev); ; prev = vma,
+ vma = vma->vm_next) {
+ if (prev) {
+ prev_end = vm_end_gap(prev);
+ if (addr < prev_end) {
+ addr = DCACHE_ALIGN(prev_end - offset) + offset;
+ if (addr < prev_end) /* handle wraparound */
+ return -ENOMEM;
+ /* If vma already violates gap, forget it */
+ if (vma && addr > vma->vm_start)
+ addr = vma->vm_start;
+ }
+ }
/* At this point: (!vma || addr < vma->vm_end). */
if (TASK_SIZE - len < addr)
return -ENOMEM;
- if (!vma || addr + len <= vma->vm_start)
+ if (!vma || addr + len <= vm_start_gap(vma))
return addr;
- addr = DCACHE_ALIGN(vma->vm_end - offset) + offset;
- if (addr < vma->vm_end) /* handle wraparound */
- return -ENOMEM;
}
}

diff -purN 302s/arch/powerpc/mm/slice.c 302h/arch/powerpc/mm/slice.c
--- 302s/arch/powerpc/mm/slice.c 2012-01-04 15:55:44.000000000 -0800
+++ 302h/arch/powerpc/mm/slice.c 2017-06-23 21:36:04.038822093 -0700
@@ -98,7 +98,7 @@ 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)
@@ -227,7 +227,7 @@ static unsigned long slice_find_area_bot
int psize, int use_cache)
{
struct vm_area_struct *vma;
- unsigned long start_addr, addr;
+ unsigned long start_addr, addr, vm_start;
struct slice_mask mask;
int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);

@@ -256,7 +256,9 @@ full_search:
addr = _ALIGN_UP(addr + 1, 1ul << SLICE_HIGH_SHIFT);
continue;
}
- if (!vma || addr + len <= vma->vm_start) {
+ if (vma)
+ vm_start = vm_start_gap(vma);
+ if (!vma || addr + len <= vm_start) {
/*
* Remember the place where we stopped the search:
*/
@@ -264,8 +266,8 @@ full_search:
mm->free_area_cache = addr + len;
return addr;
}
- if (use_cache && (addr + mm->cached_hole_size) < vma->vm_start)
- mm->cached_hole_size = vma->vm_start - addr;
+ if (use_cache && (addr + mm->cached_hole_size) < vm_start)
+ mm->cached_hole_size = vm_start - addr;
addr = vma->vm_end;
}

@@ -284,7 +286,7 @@ static unsigned long slice_find_area_top
int psize, int use_cache)
{
struct vm_area_struct *vma;
- unsigned long addr;
+ unsigned long addr, vm_start;
struct slice_mask mask;
int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);

@@ -336,7 +338,9 @@ static unsigned long slice_find_area_top
* return with success:
*/
vma = find_vma(mm, addr);
- if (!vma || (addr + len) <= vma->vm_start) {
+ if (vma)
+ vm_start = vm_start_gap(vma);
+ if (!vma || (addr + len) <= vm_start) {
/* remember the address as a hint for next time */
if (use_cache)
mm->free_area_cache = addr;
@@ -344,11 +348,11 @@ static unsigned long slice_find_area_top
}

/* remember the largest hole we saw so far */
- if (use_cache && (addr + mm->cached_hole_size) < vma->vm_start)
- mm->cached_hole_size = vma->vm_start - addr;
+ if (use_cache && (addr + mm->cached_hole_size) < vm_start)
+ mm->cached_hole_size = vm_start - addr;

/* try just below the current vma->vm_start */
- addr = vma->vm_start;
+ addr = vm_start;
}

/*
diff -purN 302s/arch/sh/mm/mmap.c 302h/arch/sh/mm/mmap.c
--- 302s/arch/sh/mm/mmap.c 2010-02-24 10:52:17.000000000 -0800
+++ 302h/arch/sh/mm/mmap.c 2017-06-23 21:36:50.758384088 -0700
@@ -47,7 +47,7 @@ unsigned long arch_get_unmapped_area(str
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
- unsigned long start_addr;
+ unsigned long start_addr, vm_start;
int do_colour_align;

if (flags & MAP_FIXED) {
@@ -75,7 +75,7 @@ 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;
}

@@ -106,15 +106,17 @@ full_search:
}
return -ENOMEM;
}
- if (likely(!vma || addr + len <= vma->vm_start)) {
+ if (vma)
+ vm_start = vm_start_gap(vma);
+ if (likely(!vma || addr + len <= vm_start)) {
/*
* Remember the place where we stopped the search:
*/
mm->free_area_cache = addr + len;
return addr;
}
- if (addr + mm->cached_hole_size < vma->vm_start)
- mm->cached_hole_size = vma->vm_start - addr;
+ if (addr + mm->cached_hole_size < vm_start)
+ mm->cached_hole_size = vm_start - addr;

addr = vma->vm_end;
if (do_colour_align)
@@ -130,6 +132,7 @@ arch_get_unmapped_area_topdown(struct fi
struct vm_area_struct *vma;
struct mm_struct *mm = current->mm;
unsigned long addr = addr0;
+ unsigned long vm_start;
int do_colour_align;

if (flags & MAP_FIXED) {
@@ -158,7 +161,7 @@ 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;
}

@@ -179,7 +182,7 @@ arch_get_unmapped_area_topdown(struct fi
/* make sure it can fit in the remaining address space */
if (likely(addr > len)) {
vma = find_vma(mm, addr-len);
- if (!vma || addr <= vma->vm_start) {
+ if (!vma || addr <= vm_start_gap(vma)) {
/* remember the address as a hint for next time */
return (mm->free_area_cache = addr-len);
}
@@ -199,20 +202,22 @@ arch_get_unmapped_area_topdown(struct fi
* return with success:
*/
vma = find_vma(mm, addr);
- if (likely(!vma || addr+len <= vma->vm_start)) {
+ if (vma)
+ vm_start = vm_start_gap(vma);
+ if (likely(!vma || addr + len <= vm_start)) {
/* remember the address as a hint for next time */
return (mm->free_area_cache = addr);
}

/* remember the largest hole we saw so far */
- if (addr + mm->cached_hole_size < vma->vm_start)
- mm->cached_hole_size = vma->vm_start - addr;
+ if (addr + mm->cached_hole_size < vm_start)
+ mm->cached_hole_size = vm_start - addr;

/* try just below the current vma->vm_start */
- addr = vma->vm_start-len;
+ addr = vm_start-len;
if (do_colour_align)
addr = COLOUR_ALIGN_DOWN(addr, pgoff);
- } while (likely(len < vma->vm_start));
+ } while (likely(len < vm_start));

bottomup:
/*
diff -purN 302s/arch/sparc/kernel/sys_sparc_32.c 302h/arch/sparc/kernel/sys_sparc_32.c
--- 302s/arch/sparc/kernel/sys_sparc_32.c 2011-01-04 16:50:19.000000000 -0800
+++ 302h/arch/sparc/kernel/sys_sparc_32.c 2017-06-22 19:35:28.166491263 -0700
@@ -71,7 +71,7 @@ unsigned long arch_get_unmapped_area(str
}
if (TASK_SIZE - PAGE_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 -purN 302s/arch/sparc/kernel/sys_sparc_64.c 302h/arch/sparc/kernel/sys_sparc_64.c
--- 302s/arch/sparc/kernel/sys_sparc_64.c 2017-06-20 16:22:15.661318622 -0700
+++ 302h/arch/sparc/kernel/sys_sparc_64.c 2017-06-23 21:38:31.169442960 -0700
@@ -117,7 +117,7 @@ unsigned long arch_get_unmapped_area(str
struct mm_struct *mm = current->mm;
struct vm_area_struct * vma;
unsigned long task_size = TASK_SIZE;
- unsigned long start_addr;
+ unsigned long start_addr, vm_start;
int do_color_align;

if (flags & MAP_FIXED) {
@@ -147,7 +147,7 @@ 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;
}

@@ -181,15 +181,17 @@ full_search:
}
return -ENOMEM;
}
- if (likely(!vma || addr + len <= vma->vm_start)) {
+ if (vma)
+ vm_start = vm_start_gap(vma);
+ if (likely(!vma || addr + len <= vm_start)) {
/*
* Remember the place where we stopped the search:
*/
mm->free_area_cache = addr + len;
return addr;
}
- if (addr + mm->cached_hole_size < vma->vm_start)
- mm->cached_hole_size = vma->vm_start - addr;
+ if (addr + mm->cached_hole_size < vm_start)
+ mm->cached_hole_size = vm_start - addr;

addr = vma->vm_end;
if (do_color_align)
@@ -237,7 +239,7 @@ 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;
}

diff -purN 302s/arch/sparc/mm/hugetlbpage.c 302h/arch/sparc/mm/hugetlbpage.c
--- 302s/arch/sparc/mm/hugetlbpage.c 2012-01-04 15:55:44.000000000 -0800
+++ 302h/arch/sparc/mm/hugetlbpage.c 2017-06-23 21:39:56.800640620 -0700
@@ -33,7 +33,7 @@ static unsigned long hugetlb_get_unmappe
struct mm_struct *mm = current->mm;
struct vm_area_struct * vma;
unsigned long task_size = TASK_SIZE;
- unsigned long start_addr;
+ unsigned long start_addr, vm_start;

if (test_thread_flag(TIF_32BIT))
task_size = STACK_TOP32;
@@ -67,15 +67,17 @@ full_search:
}
return -ENOMEM;
}
- if (likely(!vma || addr + len <= vma->vm_start)) {
+ if (vma)
+ vm_start = vm_start_gap(vma);
+ if (likely(!vma || addr + len <= vm_start)) {
/*
* Remember the place where we stopped the search:
*/
mm->free_area_cache = addr + len;
return addr;
}
- if (addr + mm->cached_hole_size < vma->vm_start)
- mm->cached_hole_size = vma->vm_start - addr;
+ if (addr + mm->cached_hole_size < vm_start)
+ mm->cached_hole_size = vm_start - addr;

addr = ALIGN(vma->vm_end, HPAGE_SIZE);
}
@@ -90,6 +92,7 @@ hugetlb_get_unmapped_area_topdown(struct
struct vm_area_struct *vma;
struct mm_struct *mm = current->mm;
unsigned long addr = addr0;
+ unsigned long vm_start;

/* This should only ever run for 32-bit processes. */
BUG_ON(!test_thread_flag(TIF_32BIT));
@@ -106,7 +109,7 @@ hugetlb_get_unmapped_area_topdown(struct
/* make sure it can fit in the remaining address space */
if (likely(addr > len)) {
vma = find_vma(mm, addr-len);
- if (!vma || addr <= vma->vm_start) {
+ if (!vma || addr <= vm_start_gap(vma)) {
/* remember the address as a hint for next time */
return (mm->free_area_cache = addr-len);
}
@@ -124,18 +127,20 @@ hugetlb_get_unmapped_area_topdown(struct
* return with success:
*/
vma = find_vma(mm, addr);
- if (likely(!vma || addr+len <= vma->vm_start)) {
+ if (vma)
+ vm_start = vm_start_gap(vma);
+ if (likely(!vma || addr + len <= vm_start)) {
/* remember the address as a hint for next time */
return (mm->free_area_cache = addr);
}

/* remember the largest hole we saw so far */
- if (addr + mm->cached_hole_size < vma->vm_start)
- mm->cached_hole_size = vma->vm_start - addr;
+ if (addr + mm->cached_hole_size < vm_start)
+ mm->cached_hole_size = vm_start - addr;

/* try just below the current vma->vm_start */
- addr = (vma->vm_start-len) & HPAGE_MASK;
- } while (likely(len < vma->vm_start));
+ addr = (vm_start - len) & HPAGE_MASK;
+ } while (likely(len < vm_start));

bottomup:
/*
@@ -182,7 +187,7 @@ 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)
diff -purN 302s/arch/tile/mm/hugetlbpage.c 302h/arch/tile/mm/hugetlbpage.c
--- 302s/arch/tile/mm/hugetlbpage.c 2011-05-18 21:06:34.000000000 -0700
+++ 302h/arch/tile/mm/hugetlbpage.c 2017-06-22 20:35:23.725762639 -0700
@@ -159,7 +159,7 @@ static unsigned long hugetlb_get_unmappe
struct hstate *h = hstate_file(file);
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
- unsigned long start_addr;
+ unsigned long start_addr, vm_start;

if (len > mm->cached_hole_size) {
start_addr = mm->free_area_cache;
@@ -185,12 +185,14 @@ full_search:
}
return -ENOMEM;
}
- if (!vma || addr + len <= vma->vm_start) {
+ if (vma)
+ vm_start = vm_start_gap(vma);
+ if (!vma || addr + len <= vm_start) {
mm->free_area_cache = addr + len;
return addr;
}
- if (addr + mm->cached_hole_size < vma->vm_start)
- mm->cached_hole_size = vma->vm_start - addr;
+ if (addr + mm->cached_hole_size < vm_start)
+ mm->cached_hole_size = vm_start - addr;
addr = ALIGN(vma->vm_end, huge_page_size(h));
}
}
@@ -204,6 +206,7 @@ static unsigned long hugetlb_get_unmappe
struct vm_area_struct *vma, *prev_vma;
unsigned long base = mm->mmap_base, addr = addr0;
unsigned long largest_hole = mm->cached_hole_size;
+ unsigned long vm_start;
int first_time = 1;

/* don't allow allocations above current base */
@@ -234,9 +237,10 @@ try_again:

/*
* new region fits between prev_vma->vm_end and
- * vma->vm_start, use it:
+ * vm_start, use it:
*/
- if (addr + len <= vma->vm_start &&
+ vm_start = vm_start_gap(vma);
+ if (addr + len <= vm_start &&
(!prev_vma || (addr >= prev_vma->vm_end))) {
/* remember the address as a hint for next time */
mm->cached_hole_size = largest_hole;
@@ -251,13 +255,13 @@ try_again:
}

/* remember the largest hole we saw so far */
- if (addr + largest_hole < vma->vm_start)
- largest_hole = vma->vm_start - addr;
+ if (addr + largest_hole < vm_start)
+ largest_hole = vm_start - addr;

/* try just below the current vma->vm_start */
- addr = (vma->vm_start - len) & huge_page_mask(h);
+ addr = (vm_start - len) & huge_page_mask(h);

- } while (len <= vma->vm_start);
+ } while (len <= vm_start);

fail:
/*
@@ -312,7 +316,7 @@ 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)
diff -purN 302s/arch/x86/kernel/sys_x86_64.c 302h/arch/x86/kernel/sys_x86_64.c
--- 302s/arch/x86/kernel/sys_x86_64.c 2017-06-20 16:22:15.749317803 -0700
+++ 302h/arch/x86/kernel/sys_x86_64.c 2017-06-22 20:36:04.897384626 -0700
@@ -126,7 +126,7 @@ arch_get_unmapped_area(struct file *filp
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
- unsigned long start_addr;
+ unsigned long start_addr, vm_start;
unsigned long begin, end;

if (flags & MAP_FIXED)
@@ -141,7 +141,7 @@ 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;
}
if (((flags & MAP_32BIT) || test_thread_flag(TIF_IA32))
@@ -172,15 +172,17 @@ full_search:
}
return -ENOMEM;
}
- if (!vma || addr + len <= vma->vm_start) {
+ if (vma)
+ vm_start = vm_start_gap(vma);
+ if (!vma || addr + len <= vm_start) {
/*
* Remember the place where we stopped the search:
*/
mm->free_area_cache = addr + len;
return addr;
}
- if (addr + mm->cached_hole_size < vma->vm_start)
- mm->cached_hole_size = vma->vm_start - addr;
+ if (addr + mm->cached_hole_size < vm_start)
+ mm->cached_hole_size = vm_start - addr;

addr = vma->vm_end;
addr = align_addr(addr, filp, 0);
@@ -196,6 +198,7 @@ arch_get_unmapped_area_topdown(struct fi
struct vm_area_struct *vma;
struct mm_struct *mm = current->mm;
unsigned long addr = addr0;
+ unsigned long vm_start;

/* requested length too big for entire address space */
if (len > TASK_SIZE)
@@ -213,7 +216,7 @@ 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;
}

@@ -232,7 +235,7 @@ arch_get_unmapped_area_topdown(struct fi
ALIGN_TOPDOWN);

vma = find_vma(mm, tmp_addr);
- if (!vma || tmp_addr + len <= vma->vm_start)
+ if (!vma || tmp_addr + len <= vm_start_gap(vma))
/* remember the address as a hint for next time */
return mm->free_area_cache = tmp_addr;
}
@@ -251,17 +254,19 @@ arch_get_unmapped_area_topdown(struct fi
* return with success:
*/
vma = find_vma(mm, addr);
- if (!vma || addr+len <= vma->vm_start)
+ if (vma)
+ vm_start = vm_start_gap(vma);
+ if (!vma || addr + len <= vm_start)
/* remember the address as a hint for next time */
return mm->free_area_cache = addr;

/* remember the largest hole we saw so far */
- if (addr + mm->cached_hole_size < vma->vm_start)
- mm->cached_hole_size = vma->vm_start - addr;
+ if (addr + mm->cached_hole_size < vm_start)
+ mm->cached_hole_size = vm_start - addr;

/* try just below the current vma->vm_start */
- addr = vma->vm_start-len;
- } while (len < vma->vm_start);
+ addr = vm_start - len;
+ } while (len < vm_start);

bottomup:
/*
diff -purN 302s/arch/x86/mm/hugetlbpage.c 302h/arch/x86/mm/hugetlbpage.c
--- 302s/arch/x86/mm/hugetlbpage.c 2017-06-20 16:22:15.773317580 -0700
+++ 302h/arch/x86/mm/hugetlbpage.c 2017-06-23 21:40:52.016123391 -0700
@@ -277,7 +277,7 @@ static unsigned long hugetlb_get_unmappe
struct hstate *h = hstate_file(file);
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
- unsigned long start_addr;
+ unsigned long start_addr, vm_start;

if (len > mm->cached_hole_size) {
start_addr = mm->free_area_cache;
@@ -303,12 +303,14 @@ full_search:
}
return -ENOMEM;
}
- if (!vma || addr + len <= vma->vm_start) {
+ if (vma)
+ vm_start = vm_start_gap(vma);
+ if (!vma || addr + len <= vm_start) {
mm->free_area_cache = addr + len;
return addr;
}
- if (addr + mm->cached_hole_size < vma->vm_start)
- mm->cached_hole_size = vma->vm_start - addr;
+ if (addr + mm->cached_hole_size < vm_start)
+ mm->cached_hole_size = vm_start - addr;
addr = ALIGN(vma->vm_end, huge_page_size(h));
}
}
@@ -322,6 +324,7 @@ static unsigned long hugetlb_get_unmappe
struct vm_area_struct *vma, *prev_vma;
unsigned long base = mm->mmap_base, addr = addr0;
unsigned long largest_hole = mm->cached_hole_size;
+ unsigned long vm_start;
int first_time = 1;

/* don't allow allocations above current base */
@@ -351,7 +354,8 @@ try_again:
* new region fits between prev_vma->vm_end and
* vma->vm_start, use it:
*/
- if (addr + len <= vma->vm_start &&
+ vm_start = vm_start_gap(vma);
+ if (addr + len <= vm_start &&
(!prev_vma || (addr >= prev_vma->vm_end))) {
/* remember the address as a hint for next time */
mm->cached_hole_size = largest_hole;
@@ -365,12 +369,12 @@ try_again:
}

/* remember the largest hole we saw so far */
- if (addr + largest_hole < vma->vm_start)
- largest_hole = vma->vm_start - addr;
+ if (addr + largest_hole < vm_start)
+ largest_hole = vm_start - addr;

/* try just below the current vma->vm_start */
- addr = (vma->vm_start - len) & huge_page_mask(h);
- } while (len <= vma->vm_start);
+ addr = (vm_start - len) & huge_page_mask(h);
+ } while (len <= vm_start);

fail:
/*
@@ -426,7 +430,7 @@ 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)
diff -purN 302s/Documentation/kernel-parameters.txt 302h/Documentation/kernel-parameters.txt
--- 302s/Documentation/kernel-parameters.txt 2017-06-20 16:22:15.389321153 -0700
+++ 302h/Documentation/kernel-parameters.txt 2017-06-21 20:07:38.174763661 -0700
@@ -2457,6 +2457,13 @@ 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.

diff -purN 302s/fs/hugetlbfs/inode.c 302h/fs/hugetlbfs/inode.c
--- 302s/fs/hugetlbfs/inode.c 2017-06-20 16:22:17.277303587 -0700
+++ 302h/fs/hugetlbfs/inode.c 2017-06-21 20:07:38.174763661 -0700
@@ -150,7 +150,7 @@ 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;
}

diff -purN 302s/fs/proc/task_mmu.c 302h/fs/proc/task_mmu.c
--- 302s/fs/proc/task_mmu.c 2017-06-20 16:22:17.401302434 -0700
+++ 302h/fs/proc/task_mmu.c 2017-06-21 20:07:38.174763661 -0700
@@ -230,11 +230,7 @@ static void show_map_vma(struct seq_file

/* 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 -purN 302s/include/linux/mm.h 302h/include/linux/mm.h
--- 302s/include/linux/mm.h 2017-06-20 16:22:17.509301429 -0700
+++ 302h/include/linux/mm.h 2017-06-22 17:47:33.388923303 -0700
@@ -1015,34 +1015,6 @@ 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 unsigned long move_page_tables(struct vm_area_struct *vma,
unsigned long old_addr, struct vm_area_struct *new_vma,
unsigned long new_addr, unsigned long len);
@@ -1462,6 +1434,7 @@ unsigned long ra_submit(struct file_ra_s
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);

@@ -1490,6 +1463,30 @@ 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;
diff -purN 302s/mm/memory.c 302h/mm/memory.c
--- 302s/mm/memory.c 2017-06-20 16:22:17.725299419 -0700
+++ 302h/mm/memory.c 2017-06-21 20:07:38.178763623 -0700
@@ -1605,12 +1605,6 @@ 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
@@ -1761,11 +1755,6 @@ int __get_user_pages(struct task_struct
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)
@@ -3122,40 +3111,6 @@ 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.
@@ -3174,10 +3129,6 @@ static int do_anonymous_page(struct mm_s
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, address) < 0)
- return VM_FAULT_SIGSEGV;
-
/* Use the zero-page for reads */
if (!(flags & FAULT_FLAG_WRITE)) {
entry = pte_mkspecial(pfn_pte(my_zero_pfn(address),
diff -purN 302s/mm/mmap.c 302h/mm/mmap.c
--- 302s/mm/mmap.c 2017-06-20 16:22:17.733299345 -0700
+++ 302h/mm/mmap.c 2017-06-23 21:42:54.430977017 -0700
@@ -245,6 +245,7 @@ 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;

down_write(&mm->mmap_sem);
@@ -289,7 +290,8 @@ 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. */
@@ -1368,8 +1370,8 @@ 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;
- unsigned long start_addr;
+ struct vm_area_struct *vma, *prev;
+ unsigned long start_addr, vm_start, prev_end;

if (len > TASK_SIZE - mmap_min_addr)
return -ENOMEM;
@@ -1379,9 +1381,10 @@ 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;
}
if (len > mm->cached_hole_size) {
@@ -1392,7 +1395,17 @@ arch_get_unmapped_area(struct file *filp
}

full_search:
- for (vma = find_vma(mm, addr); ; vma = vma->vm_next) {
+ for (vma = find_vma_prev(mm, addr, &prev); ; prev = vma,
+ vma = vma->vm_next) {
+ if (prev) {
+ prev_end = vm_end_gap(prev);
+ if (addr < prev_end) {
+ addr = prev_end;
+ /* If vma already violates gap, forget it */
+ if (vma && addr > vma->vm_start)
+ addr = vma->vm_start;
+ }
+ }
/* At this point: (!vma || addr < vma->vm_end). */
if (TASK_SIZE - len < addr) {
/*
@@ -1407,16 +1420,16 @@ full_search:
}
return -ENOMEM;
}
- if (!vma || addr + len <= vma->vm_start) {
+ vm_start = vma ? vm_start_gap(vma) : TASK_SIZE;
+ if (addr + len <= vm_start) {
/*
* Remember the place where we stopped the search:
*/
mm->free_area_cache = addr + len;
return addr;
}
- if (addr + mm->cached_hole_size < vma->vm_start)
- mm->cached_hole_size = vma->vm_start - addr;
- addr = vma->vm_end;
+ if (addr + mm->cached_hole_size < vm_start)
+ mm->cached_hole_size = vm_start - addr;
}
}
#endif
@@ -1442,9 +1455,10 @@ 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;
+ unsigned long vm_start, prev_end;
unsigned long low_limit = max(PAGE_SIZE, mmap_min_addr);

/* requested length too big for entire address space */
@@ -1457,9 +1471,10 @@ 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;
}

@@ -1474,8 +1489,9 @@ arch_get_unmapped_area_topdown(struct fi

/* make sure it can fit in the remaining address space */
if (addr >= low_limit + len) {
- vma = find_vma(mm, addr-len);
- if (!vma || addr <= vma->vm_start)
+ vma = find_vma_prev(mm, addr-len, &prev);
+ if ((!vma || addr <= vm_start_gap(vma)) &&
+ (!prev || addr-len >= vm_end_gap(prev)))
/* remember the address as a hint for next time */
return (mm->free_area_cache = addr-len);
}
@@ -1491,18 +1507,21 @@ arch_get_unmapped_area_topdown(struct fi
* else if new region fits below vma->vm_start,
* return with success:
*/
- vma = find_vma(mm, addr);
- if (!vma || addr+len <= vma->vm_start)
+ vma = find_vma_prev(mm, addr, &prev);
+ vm_start = vma ? vm_start_gap(vma) : mm->mmap_base;
+ prev_end = prev ? vm_end_gap(prev) : low_limit;
+
+ if (addr + len <= vm_start && addr >= prev_end)
/* remember the address as a hint for next time */
return (mm->free_area_cache = addr);

/* remember the largest hole we saw so far */
- if (addr + mm->cached_hole_size < vma->vm_start)
- mm->cached_hole_size = vma->vm_start - addr;
+ if (addr + mm->cached_hole_size < vm_start)
+ mm->cached_hole_size = vm_start - addr;

/* try just below the current vma->vm_start */
- addr = vma->vm_start-len;
- } while (vma->vm_start >= low_limit + len);
+ addr = vm_start - len;
+ } while (vm_start >= low_limit + len);

bottomup:
/*
@@ -1647,21 +1666,19 @@ out:
* 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, 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 > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur))
+ if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur))
return -ENOMEM;

/* mlock limit tests */
@@ -1703,32 +1720,40 @@ static int acct_stack_growth(struct vm_a
*/
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) {
@@ -1758,27 +1783,36 @@ int expand_upwards(struct vm_area_struct
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_file_mmap(NULL, 0, 0, 0, address, 1);
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) {
@@ -1802,6 +1836,22 @@ int expand_downwards(struct vm_area_stru
return error;
}

+/* 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)
{