linux-kernel - [PATCH] fs/ntfs3: Initialize new folios before use

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Message-Id: <20251126220251.856795-1-kubik.bartlomiej@gmail.com>
Date: Wed, 26 Nov 2025 23:02:51 +0100
From: Bartlomiej Kubik <kubik.bartlomiej@...il.com>
To: almaz.alexandrovich@...agon-software.com
Cc: ntfs3@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	david.hunter.linux@...il.com,
	skhan@...uxfoundation.org,
	khalid@...nel.org,
	linux-kernel-mentees@...ts.linux.dev,
	Bartlomiej Kubik <kubik.bartlomiej@...il.com>,
	syzbot+08d8956768c96a2c52cf@...kaller.appspotmail.com
Subject: [PATCH] fs/ntfs3: Initialize new folios before use

KMSAN reports an uninitialized value in longest_match_std(), invoked
from ntfs_compress_write(). When new folios are allocated without being
marked uptodate and ni_read_frame() is skipped because the caller expects
the frame to be completely overwritten, some reserved folios may remain
only partially filled, leaving the rest memory uninitialized.

Fixes: 584f60ba22f7 ("ntfs3: Convert ntfs_get_frame_pages() to use a folio")
Tested-by: syzbot+08d8956768c96a2c52cf@...kaller.appspotmail.com
Reported-by: syzbot+08d8956768c96a2c52cf@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=08d8956768c96a2c52cf

Signed-off-by: Bartlomiej Kubik <kubik.bartlomiej@...il.com>
---
 fs/ntfs3/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ntfs3/file.c b/fs/ntfs3/file.c
index 4c90ec2fa2ea..00df27876c50 100644
--- a/fs/ntfs3/file.c
+++ b/fs/ntfs3/file.c
@@ -930,7 +930,7 @@ static int ntfs_get_frame_pages(struct address_space *mapping, pgoff_t index,

 		folio = __filemap_get_folio(mapping, index,
 					    FGP_LOCK | FGP_ACCESSED | FGP_CREAT,
-					    gfp_mask);
+					    gfp_mask | __GFP_ZERO);
 		if (IS_ERR(folio)) {
 			while (npages--) {
 				folio = page_folio(pages[npages]);
--
2.39.5