Re: [PATCH 4.19 026/239] f2fs: fix to do sanity check in is_alive()

[Chao Yu]

On 2022/1/25 4:36, Pavel Machek wrote:
> Hi!
>
> > From: Chao Yu <chao@xxxxxxxxxx>
> >
> > commit 77900c45ee5cd5da63bd4d818a41dbdf367e81cd upstream.
> >
> > In fuzzed image, SSA table may indicate that a data block belongs to
> > invalid node, which node ID is out-of-range (0, 1, 2 or max_nid), in
> > order to avoid migrating inconsistent data in such corrupted image,
> > let's do sanity check anyway before data block migration.
>
> This may be good idea, but AFAICT this leads to leak of page reference.

Hi Pavel,

Oops, you're right, my bad.

> > +++ b/fs/f2fs/gc.c
> > @@ -589,6 +589,9 @@ static bool is_alive(struct f2fs_sb_info
> >   		set_sbi_flag(sbi, SBI_NEED_FSCK);
> >   	}
> >   
> > +	if (f2fs_check_nid_range(sbi, dni->ino))
> > +		return false;
> > +
> >   	*nofs = ofs_of_node(node_page);
> >   	source_blkaddr = datablock_addr(NULL, node_page, ofs_in_node);
> >   	f2fs_put_page(node_page, 1);
>
> AFAICT f2fs_put_page() needs to be done in the error path, too.
>
> (Problem seems to exist in mainline, too).
>
> Something like this?

Could you please send a formal patch to f2fs mailing list for better review?

Anyway, thanks a lot for the report and the patch!

Thanks,

> Signed-off-by: Pavel Machek <pavel@xxxxxxx>
>
> Best regards,
> 								Pavel
>
> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
> index ee308a8de432..e020804f7b07 100644
> --- a/fs/f2fs/gc.c
> +++ b/fs/f2fs/gc.c
> @@ -1038,8 +1038,10 @@ static bool is_alive(struct f2fs_sb_info *sbi, struct f2fs_summary *sum,
>   		set_sbi_flag(sbi, SBI_NEED_FSCK);
>   	}
>   
> -	if (f2fs_check_nid_range(sbi, dni->ino))
> +	if (f2fs_check_nid_range(sbi, dni->ino)) {
> +		f2fs_put_page(node_page, 1);
>   		return false;
> +	}
>   
>   	*nofs = ofs_of_node(node_page);
>   	source_blkaddr = data_blkaddr(NULL, node_page, ofs_in_node);