The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 68f6bd128e75a032432eda9d16676ed2969a1096 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2026010541-comply-poet-d4a1@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 68f6bd128e75a032432eda9d16676ed2969a1096 Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" willy@infradead.org Date: Fri, 18 Jul 2025 20:53:58 +0100 Subject: [PATCH] ntfs: Do not overwrite uptodate pages

When reading a compressed file, we may read several pages in addition to the one requested. The current code will overwrite pages in the page cache with the data from disc which can definitely result in changes that have been made being lost.

For example if we have four consecutie pages ABCD in the file compressed into a single extent, on first access, we'll bring in ABCD. Then we write to page B. Memory pressure results in the eviction of ACD. When we attempt to write to page C, we will overwrite the data in page B with the data currently on disk.

I haven't investigated the decompression code to check whether it's OK to overwrite a clean page or whether it might be possible to see corrupt data. Out of an abundance of caution, decline to overwrite uptodate pages, not just dirty pages.

Fixes: 4342306f0f0d (fs/ntfs3: Add file operations and implementation) Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org Cc: stable@vger.kernel.org Signed-off-by: Konstantin Komarov almaz.alexandrovich@paragon-software.com

diff --git a/fs/ntfs3/frecord.c b/fs/ntfs3/frecord.c index e1832b66718f..e44181185526 100644 --- a/fs/ntfs3/frecord.c +++ b/fs/ntfs3/frecord.c @@ -2020,6 +2020,29 @@ int ni_fiemap(struct ntfs_inode *ni, struct fiemap_extent_info *fieinfo, return err; }

+static struct page *ntfs_lock_new_page(struct address_space *mapping, + pgoff_t index, gfp_t gfp) +{ + struct folio *folio = __filemap_get_folio(mapping, index, + FGP_LOCK | FGP_ACCESSED | FGP_CREAT, gfp); + struct page *page; + + if (IS_ERR(folio)) + return ERR_CAST(folio); + + if (!folio_test_uptodate(folio)) + return folio_file_page(folio, index); + + /* Use a temporary page to avoid data corruption */ + folio_unlock(folio); + folio_put(folio); + page = alloc_page(gfp); + if (!page) + return ERR_PTR(-ENOMEM); + __SetPageLocked(page); + return page; +} + /* * ni_readpage_cmpr * @@ -2074,9 +2097,9 @@ int ni_readpage_cmpr(struct ntfs_inode *ni, struct folio *folio) if (i == idx) continue;

- pg = find_or_create_page(mapping, index, gfp_mask); - if (!pg) { - err = -ENOMEM; + pg = ntfs_lock_new_page(mapping, index, gfp_mask); + if (IS_ERR(pg)) { + err = PTR_ERR(pg); goto out1; } pages[i] = pg; @@ -2175,13 +2198,13 @@ int ni_decompress_file(struct ntfs_inode *ni) for (i = 0; i < pages_per_frame; i++, index++) { struct page *pg;

- pg = find_or_create_page(mapping, index, gfp_mask); - if (!pg) { + pg = ntfs_lock_new_page(mapping, index, gfp_mask); + if (IS_ERR(pg)) { while (i--) { unlock_page(pages[i]); put_page(pages[i]); } - err = -ENOMEM; + err = PTR_ERR(pg); goto out; } pages[i] = pg;