linux-kernel - [PATCH 1/2] mm: shmem: fix incorrect index alignment for within

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <77d8ef76a7d3d646e9225e9af88a76549a68aab1.1734593154.git.baolin.wang@linux.alibaba.com>
Date: Thu, 19 Dec 2024 15:30:08 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: akpm@...ux-foundation.org,
	hughd@...gle.com
Cc: david@...hat.com,
	baolin.wang@...ux.alibaba.com,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] mm: shmem: fix incorrect index alignment for within_size policy

With enabling the shmem per-size within_size policy, using an incorrect
'order' size to round_up() the index can lead to incorrect i_size checks,
resulting in an inappropriate large orders being returned.

Changing to use '1 << order' to round_up() the index to fix this issue.
Additionally, adding an 'aligned_index' variable to avoid affecting the
index checks.

Fixes: e7a2ab7b3bb5 ("mm: shmem: add mTHP support for anonymous shmem")
Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
---
Hi Andrew,

These two bugfix patches are based on the mm-hotfixes-unstable branch,
and this patch has a slight conflict with my previous patch set:
"Support large folios for tmpfs". However, I think the conflicts are
easy to resolve. If you need me to rebase and resend the
"Support large folios for tmpfs" patch set, please let me know.
Sorry for the troubles :)
---
 mm/shmem.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index f6fb053ac50d..dec659e84562 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1689,6 +1689,7 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode,
 	unsigned long mask = READ_ONCE(huge_shmem_orders_always);
 	unsigned long within_size_orders = READ_ONCE(huge_shmem_orders_within_size);
 	unsigned long vm_flags = vma ? vma->vm_flags : 0;
+	pgoff_t aligned_index;
 	bool global_huge;
 	loff_t i_size;
 	int order;
@@ -1723,9 +1724,9 @@ unsigned long shmem_allowable_huge_orders(struct inode *inode,
 	/* Allow mTHP that will be fully within i_size. */
 	order = highest_order(within_size_orders);
 	while (within_size_orders) {
-		index = round_up(index + 1, order);
+		aligned_index = round_up(index + 1, 1 << order);
 		i_size = round_up(i_size_read(inode), PAGE_SIZE);
-		if (i_size >> PAGE_SHIFT >= index) {
+		if (i_size >> PAGE_SHIFT >= aligned_index) {
 			mask |= within_size_orders;
 			break;
 		}
-- 
2.39.3