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authorOleg Nesterov <oleg@redhat.com>2017-07-10 15:49:54 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-07-10 16:32:33 -0700
commit32e4e6d5cbb0c0e427391635991fe65e17797af8 (patch)
tree99fd2fe16b0823ff35bf616f1f3dad661e21cec9 /mm/mmap.c
parent561b5e0709e4a248c67d024d4d94b6e31e3edf2f (diff)
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mm/mmap.c: expand_downwards: don't require the gap if !vm_prev
expand_stack(vma) fails if address < stack_guard_gap even if there is no vma->vm_prev. I don't think this makes sense, and we didn't do this before the recent commit 1be7107fbe18 ("mm: larger stack guard gap, between vmas"). We do not need a gap in this case, any address is fine as long as security_mmap_addr() doesn't object. This also simplifies the code, we know that address >= prev->vm_end and thus underflow is not possible. Link: http://lkml.kernel.org/r/20170628175258.GA24881@redhat.com Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Hugh Dickins <hughd@google.com> Cc: Larry Woodman <lwoodman@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/mmap.c')
-rw-r--r--mm/mmap.c10
1 files changed, 3 insertions, 7 deletions
diff --git a/mm/mmap.c b/mm/mmap.c
index d1902872414f..49c56b811b03 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2316,7 +2316,6 @@ int expand_downwards(struct vm_area_struct *vma,
{
struct mm_struct *mm = vma->vm_mm;
struct vm_area_struct *prev;
- unsigned long gap_addr;
int error;
address &= PAGE_MASK;
@@ -2325,15 +2324,12 @@ int expand_downwards(struct vm_area_struct *vma,
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 &&
+ /* Check that both stack segments have the same anon_vma? */
+ if (prev && !(prev->vm_flags & VM_GROWSDOWN) &&
(prev->vm_flags & (VM_WRITE|VM_READ|VM_EXEC))) {
- if (!(prev->vm_flags & VM_GROWSDOWN))
+ if (address - prev->vm_end < stack_guard_gap)
return -ENOMEM;
- /* Check that both stack segments have the same anon_vma? */
}
/* We must make sure the anon_vma is allocated. */