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Date:   Wed, 16 Sep 2020 08:16:22 +0200
From:   Greg KH <greg@kroah.com>
To:     Anant Thazhemadam <anant.thazhemadam@gmail.com>
Cc:     linux-kernel@vger.kernel.org,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        linux-fsdevel@vger.kernel.org,
        syzbot+4191a44ad556eacc1a7a@syzkaller.appspotmail.com,
        linux-kernel-mentees@lists.linuxfoundation.org
Subject: Re: [Linux-kernel-mentees] [PATCH] fs: fix KMSAN uninit-value bug by
 initializing nd in do_file_open_root
Message-ID: <20200916061622.GA142621@kroah.com>
References: <20200916052657.18683-1-anant.thazhemadam@gmail.com>
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On Wed, Sep 16, 2020 at 10:56:56AM +0530, Anant Thazhemadam wrote:
> The KMSAN bug report for the bug indicates that there exists;
> Local variable ----nd@do_file_open_root created at:
>  do_file_open_root+0xa4/0xb40 fs/namei.c:3385
>  do_file_open_root+0xa4/0xb40 fs/namei.c:3385

What does this "error" mean?

> Initializing nd fixes this issue, and doesn't break anything else either
> 
> Fixes: https://syzkaller.appspot.com/bug?extid=4191a44ad556eacc1a7a
> Reported-by: syzbot+4191a44ad556eacc1a7a@syzkaller.appspotmail.com
> Tested-by: syzbot+4191a44ad556eacc1a7a@syzkaller.appspotmail.com
> Signed-off-by: Anant Thazhemadam <anant.thazhemadam@gmail.com>
> ---
>  fs/namei.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index e99e2a9da0f7..b27382586209 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -3404,7 +3404,7 @@ struct file *do_filp_open(int dfd, struct filename *pathname,
>  struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
>  		const char *name, const struct open_flags *op)
>  {
> -	struct nameidata nd;
> +	struct nameidata nd = {};

What exactly does setting this structure to all 0 fix here that is
currently "broken"?

confused,

greg k-h