linux-kernel - [PATCH 03/11] mm: Zero the head page, not the tail page

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

Date:   Mon, 24 Aug 2020 16:16:52 +0100
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        "Darrick J . Wong" <darrick.wong@...cle.com>,
        linux-block@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 03/11] mm: Zero the head page, not the tail page

Pass the head page to zero_user_segment(), not the tail page, and adjust
the byte offsets appropriately.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 mm/shmem.c    | 7 +++++++
 mm/truncate.c | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/mm/shmem.c b/mm/shmem.c
index 271548ca20f3..77982149b437 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -958,11 +958,18 @@ static void shmem_undo_range(struct inode *inode, loff_t lstart, loff_t lend,
 		struct page *page = NULL;
 		shmem_getpage(inode, start - 1, &page, SGP_READ);
 		if (page) {
+			struct page *head = thp_head(page);
 			unsigned int top = PAGE_SIZE;
 			if (start > end) {
 				top = partial_end;
 				partial_end = 0;
 			}
+			if (head != page) {
+				unsigned int diff = start - 1 - head->index;
+				partial_start += diff << PAGE_SHIFT;
+				top += diff << PAGE_SHIFT;
+				page = head;
+			}
 			zero_user_segment(page, partial_start, top);
 			set_page_dirty(page);
 			unlock_page(page);
diff --git a/mm/truncate.c b/mm/truncate.c
index dd9ebc1da356..152974888124 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -374,12 +374,19 @@ void truncate_inode_pages_range(struct address_space *mapping,
 	if (partial_start) {
 		struct page *page = find_lock_page(mapping, start - 1);
 		if (page) {
+			struct page *head = thp_head(page);
 			unsigned int top = PAGE_SIZE;
 			if (start > end) {
 				/* Truncation within a single page */
 				top = partial_end;
 				partial_end = 0;
 			}
+			if (head != page) {
+				unsigned int diff = start - 1 - head->index;
+				partial_start += diff << PAGE_SHIFT;
+				top += diff << PAGE_SHIFT;
+				page = head;
+			}
 			wait_on_page_writeback(page);
 			zero_user_segment(page, partial_start, top);
 			cleancache_invalidate_page(mapping, page);
-- 
2.28.0