The VMA count limit check in do_mmap() and do_brk_flags() uses a
strict inequality (>), which allows a process's VMA count to exceed
the configured sysctl_max_map_count limit by one.
A process with mm->map_count == sysctl_max_map_count will incorrectly
pass this check and then exceed the limit upon allocation of a new VMA
when its map_count is incremented.
Other VMA allocation paths, such as split_vma(), already use the
correct, inclusive (>=) comparison.
Fix this bug by changing the comparison to be inclusive in do_mmap()
and do_brk_flags(), bringing them in line with the correct behavior
of other allocation paths.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: "Liam R. Howlett" <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Pedro Falcato <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Reviewed-by: Lorenzo Stoakes <[email protected]>
Reviewed-by: Pedro Falcato <[email protected]>
Acked-by: SeongJae Park <[email protected]>
Signed-off-by: Kalesh Singh <[email protected]>
---
Changes in v3:
- Collect Reviewed-by and Acked-by tags.
Changes in v2:
- Fix mmap check, per Pedro
mm/mmap.c | 2 +-
mm/vma.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index 644f02071a41..da2cbdc0f87b 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -374,7 +374,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
return -EOVERFLOW;
/* Too many mappings? */
- if (mm->map_count > sysctl_max_map_count)
+ if (mm->map_count >= sysctl_max_map_count)
return -ENOMEM;
/*
diff --git a/mm/vma.c b/mm/vma.c
index a2e1ae954662..fba68f13e628 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -2797,7 +2797,7 @@ int do_brk_flags(struct vma_iterator *vmi, struct
vm_area_struct *vma,
if (!may_expand_vm(mm, vm_flags, len >> PAGE_SHIFT))
return -ENOMEM;
- if (mm->map_count > sysctl_max_map_count)
+ if (mm->map_count >= sysctl_max_map_count)
return -ENOMEM;
if (security_vm_enough_memory_mm(mm, len >> PAGE_SHIFT))
--
2.51.0.760.g7b8bcc2412-goog
