Re: [syzbot] WARNING in wnd_init

[Enrico Mioso <mrkiko.rs@gmail.com>]

Hello all!

Is this the expected fix for the issue?
Shouldn't the value be sanitized somehow?
This is intended to be an "honest" question - I am not an experienced kernel nor filesystem programmer, just wondering...

Enrico


On Sun, 2 Oct 2022, Tetsuo Handa wrote:

> Date: Sun, 2 Oct 2022 16:37:34
> From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
> To: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
> Cc: syzbot <syzbot+fa4648a5446460b7b963@syzkaller.appspotmail.com>,
>     syzkaller-bugs@googlegroups.com, ntfs3@lists.linux.dev,
>     Kari Argillander <kari.argillander@gmail.com>
> Subject: Re: [syzbot] WARNING in wnd_init
> 
> syzbot is reporting too large allocation at wnd_init() [1], for a crafted
> filesystem can become wnd->nwnd close to UINT_MAX. Add __GFP_NOWARN in
> order to avoid too large allocation warning, than exhausting memory by
> using kvcalloc().
>
> Link: https://syzkaller.appspot.com/bug?extid=fa4648a5446460b7b963 [1]
> Reported-by: syzot <syzbot+fa4648a5446460b7b963@syzkaller.appspotmail.com>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> ---
> fs/ntfs3/bitmap.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/ntfs3/bitmap.c b/fs/ntfs3/bitmap.c
> index 5d44ceac855b..90f3c4e84856 100644
> --- a/fs/ntfs3/bitmap.c
> +++ b/fs/ntfs3/bitmap.c
> @@ -661,7 +661,7 @@ int wnd_init(struct wnd_bitmap *wnd, struct super_block *sb, size_t nbits)
> 	if (!wnd->bits_last)
> 		wnd->bits_last = wbits;
>
> -	wnd->free_bits = kcalloc(wnd->nwnd, sizeof(u16), GFP_NOFS);
> +	wnd->free_bits = kcalloc(wnd->nwnd, sizeof(u16), GFP_NOFS | __GFP_NOWARN);
> 	if (!wnd->free_bits)
> 		return -ENOMEM;
>
> -- 
> 2.34.1
>
>
>