netdev - Re: [PATCH nf] netfilter: xt_RATEEST: reject non-null terminated string from userspace

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Message-ID: <CAHk-=wjB83CZvzp88Axc278L+uSKEdztA9OO7kjx64R7Y9n31A@mail.gmail.com>
Date:   Tue, 22 Dec 2020 14:29:57 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Florian Westphal <fw@...len.de>
Cc:     NetFilter <netfilter-devel@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        syzbot <syzbot+e86f7c428c8c50db65b4@...kaller.appspotmail.com>
Subject: Re: [PATCH nf] netfilter: xt_RATEEST: reject non-null terminated
 string from userspace

On Tue, Dec 22, 2020 at 2:24 PM Florian Westphal <fw@...len.de> wrote:
>
> strlcpy assumes src is a c-string. Check info->name before its used.

If strlcpy is the only problem, then the fix is to use strscpy(),
which doesn't have the design mistake that strlcpy has.

Of course, if the size limit of the source and the destination differ
(ie if you really want to limit the source to one thing, and the
destination to another - there are in theory valid cases where that
happens), then there are no useful helper functions for that.

                Linus