diff options
| -rw-r--r-- | mm/mmap.c | 36 |
1 files changed, 28 insertions, 8 deletions
diff --git a/mm/mmap.c b/mm/mmap.c index ed70a68e882a..02c09f33df8b 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1811,10 +1811,10 @@ detach_vmas_to_be_unmapped(struct mm_struct *mm, struct vm_area_struct *vma, } /* - * Split a vma into two pieces at address 'addr', a new vma is allocated - * either for the first part or the tail. + * __split_vma() bypasses sysctl_max_map_count checking. We use this on the + * munmap path where it doesn't make sense to fail. */ -int split_vma(struct mm_struct * mm, struct vm_area_struct * vma, +static int __split_vma(struct mm_struct * mm, struct vm_area_struct * vma, unsigned long addr, int new_below) { struct mempolicy *pol; @@ -1824,9 +1824,6 @@ int split_vma(struct mm_struct * mm, struct vm_area_struct * vma, ~(huge_page_mask(hstate_vma(vma))))) return -EINVAL; - if (mm->map_count >= sysctl_max_map_count) - return -ENOMEM; - new = kmem_cache_alloc(vm_area_cachep, GFP_KERNEL); if (!new) return -ENOMEM; @@ -1866,6 +1863,19 @@ int split_vma(struct mm_struct * mm, struct vm_area_struct * vma, return 0; } +/* + * Split a vma into two pieces at address 'addr', a new vma is allocated + * either for the first part or the tail. + */ +int split_vma(struct mm_struct *mm, struct vm_area_struct *vma, + unsigned long addr, int new_below) +{ + if (mm->map_count >= sysctl_max_map_count) + return -ENOMEM; + + return __split_vma(mm, vma, addr, new_below); +} + /* Munmap is split into 2 main parts -- this part which finds * what needs doing, and the areas themselves, which do the * work. This now handles partial unmappings. @@ -1901,7 +1911,17 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len) * places tmp vma above, and higher split_vma places tmp vma below. */ if (start > vma->vm_start) { - int error = split_vma(mm, vma, start, 0); + int error; + + /* + * Make sure that map_count on return from munmap() will + * not exceed its limit; but let map_count go just above + * its limit temporarily, to help free resources as expected. + */ + if (end < vma->vm_end && mm->map_count >= sysctl_max_map_count) + return -ENOMEM; + + error = __split_vma(mm, vma, start, 0); if (error) return error; prev = vma; @@ -1910,7 +1930,7 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len) /* Does it split the last one? */ last = find_vma(mm, end); if (last && end > last->vm_start) { - int error = split_vma(mm, last, end, 1); + int error = __split_vma(mm, last, end, 1); if (error) return error; } |