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

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Message-ID: <7b477b93-a521-4f87-9bee-e17505e46690@paragon-software.com>
Date: Tue, 9 Dec 2025 14:37:05 +0100
From: Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
To: Bartlomiej Kubik <kubik.bartlomiej@...il.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>,
	<syzbot+08d8956768c96a2c52cf@...kaller.appspotmail.com>
Subject: Re: [PATCH] fs/ntfs3: Initialize new folios before use

On 11/26/25 23:02, Bartlomiej Kubik wrote:

> 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
>
Queued for the next merge window, thanks.

Regards,
Konstantin