fs/ntfs3: Initialize new folios before use

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

Posted by Bartlomiej Kubik 2 months, 1 week ago

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@syzkaller.appspotmail.com
Reported-by: syzbot+08d8956768c96a2c52cf@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=08d8956768c96a2c52cf

Signed-off-by: Bartlomiej Kubik <kubik.bartlomiej@gmail.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

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

Posted by Konstantin Komarov 2 months ago

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@syzkaller.appspotmail.com
> Reported-by: syzbot+08d8956768c96a2c52cf@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=08d8956768c96a2c52cf
>
> Signed-off-by: Bartlomiej Kubik <kubik.bartlomiej@gmail.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