[PATCH v2 44/47] mm/vma: don't leak the charge for stack growth

[David Hildenbrand (Arm)]

acct_stack_growth() charges stack expansion even without VM_ACCOUNT.
This can happen for read-only or MAP_NORESERVE mappings created with
MAP_GROWSDOWN. Unmapping these VMAs does not release the charge, leaking
Committed_AS.

Only check and charge growth for VM_ACCOUNT VMAs, matching mremap().
Unaccounted growth skips the overcommit check while remaining subject
to the other stack-growth limits.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
Reviewed-by: Pedro Falcato <pfalcato@xxxxxxx>
Reviewed-by: Harry Yoo (Meta) <harry@xxxxxxxxxx>
Signed-off-by: David Hildenbrand (Arm) <david@xxxxxxxxxx>
---
 mm/vma.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/vma.c b/mm/vma.c
index acdf00346cda..695d0be85ac8 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -3391,7 +3391,8 @@ static int acct_stack_growth(struct vm_area_struct *vma,
 	 * Overcommit..  This must be the final test, as it will
 	 * update security statistics.
 	 */
-	if (security_vm_enough_memory_mm(mm, grow))
+	if (vma_test(vma, VMA_ACCOUNT_BIT) &&
+	    security_vm_enough_memory_mm(mm, grow))
 		return -ENOMEM;
 
 	return 0;

-- 
2.43.0