linux-kernel - Re: KASAN: use-after-free Read in path

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20190325224959.GQ2217@ZenIV.linux.org.uk>
Date:   Mon, 25 Mar 2019 22:49:59 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        syzbot <syzbot+7a8ba368b47fdefca61e@...kaller.appspotmail.com>,
        Alexei Starovoitov <ast@...nel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: KASAN: use-after-free Read in path_lookupat

On Mon, Mar 25, 2019 at 11:04:53PM +0100, Daniel Borkmann wrote:

> +static void bpf_destroy_inode_deferred(struct rcu_head *head)
> +{
> +	struct inode *inode = container_of(head, struct inode, i_rcu);
> +	enum bpf_type type;
> +
> +	if (S_ISLNK(inode->i_mode))
> +		kfree(inode->i_link);
> +	if (!bpf_inode_type(inode, &type))
> +		bpf_any_put(inode->i_private, type);
> +	free_inode_nonrcu(inode);
> +}

Umm...  Can bpf_any_put() can be called in that context?  It's going
to run in softirq; if that's OK (I'm not familiar enough with BPF guts
to tell), sure, that's probably the best approach.

Note, BTW, that it's obviously -stable fodder, so any splitting
of ->destroy_inode() would live on top of that fix.