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Date:   Mon, 26 Nov 2018 15:25:29 -0800
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Sheng Yong <shengyong1@huawei.com>
Cc:     linux-kernel@vger.kernel.org,
        linux-f2fs-devel@lists.sourceforge.net,
        "gongchen (E)" <gongchen4@huawei.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: check memory boundary by insane namelen
Message-ID: <20181126232529.GC55960@jaegeuk-macbookpro.roam.corp.google.com>
References: <20181115075040.83500-1-jaegeuk@kernel.org>
 <3d213d40-a4b0-6e60-87b2-81e66866ac4c@huawei.com>
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On 11/23, Sheng Yong wrote:
> Hi, Jaegeuk and Chao,
> 
> On 2018/11/15 15:50, Jaegeuk Kim wrote:
> > If namelen is corrupted to have very long value, fill_dentries can copy
> > wrong memory area.
> > 
> Is there any scenario that could hit this corruption? Or this is triggered
> by fuzzing injection?

Hi Sheng,

It's from a fuzzing test.

Thanks,

> 
> thanks,
> Sheng Yong
> 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> >   fs/f2fs/dir.c | 12 +++++++++++-
> >   1 file changed, 11 insertions(+), 1 deletion(-)
> > 
> > diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
> > index bacc667950b6..c0c845da12fa 100644
> > --- a/fs/f2fs/dir.c
> > +++ b/fs/f2fs/dir.c
> > @@ -808,6 +808,17 @@ int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d,
> >   		de_name.name = d->filename[bit_pos];
> >   		de_name.len = le16_to_cpu(de->name_len);
> > +		/* check memory boundary before moving forward */
> > +		bit_pos += GET_DENTRY_SLOTS(le16_to_cpu(de->name_len));
> > +		if (unlikely(bit_pos > d->max)) {
> > +			f2fs_msg(sbi->sb, KERN_WARNING,
> > +				"%s: corrupted namelen=%d, run fsck to fix.",
> > +				__func__, le16_to_cpu(de->name_len));
> > +			set_sbi_flag(sbi, SBI_NEED_FSCK);
> > +			err = -EINVAL;
> > +			goto out;
> > +		}
> > +
> >   		if (f2fs_encrypted_inode(d->inode)) {
> >   			int save_len = fstr->len;
> > @@ -830,7 +841,6 @@ int f2fs_fill_dentries(struct dir_context *ctx, struct f2fs_dentry_ptr *d,
> >   		if (readdir_ra)
> >   			f2fs_ra_node_page(sbi, le32_to_cpu(de->ino));
> > -		bit_pos += GET_DENTRY_SLOTS(le16_to_cpu(de->name_len));
> >   		ctx->pos = start_pos + bit_pos;
> >   	}
> >   out:
> >