[PATCH 5.10.y] mm/vma: don't leak the charge for stack growth

[Sasha Levin <sashal@kernel.org>]

From: "David Hildenbrand (Arm)" <david@kernel.org>

[ Upstream commit b1ee87802111156e27557e82acc31fa7dfc76e2a ]

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@vger.kernel.org
Reported-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Harry Yoo (Meta) <harry@kernel.org>
Tested-by: Muhammad Usama Anjum <usama.anjum@arm.com>
Link: https://patch.msgid.link/20261031-fixes_core-v3-44-d6437171ecc3@kernel.org
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
[ sashal: replaced vma_test(vma, VMA_ACCOUNT_BIT) with a direct VM_ACCOUNT check on vma->vm_flags ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 mm/mmap.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index 290822968e218..8b819f050ce50 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2399,7 +2399,8 @@ 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->vm_flags & VM_ACCOUNT) &&
+	    security_vm_enough_memory_mm(mm, grow))
 		return -ENOMEM;
 
 	return 0;
-- 
2.53.0