From: Kees Cook <keescook@chromium.org>
To: Azeem Shaikh <azeemshaikh38@gmail.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-hardening@vger.kernel.org, linux-usb@vger.kernel.org,
linux-kernel@vger.kernel.org,
Albert Briscoe <albertsbriscoe@gmail.com>,
Benjamin Tissoires <benjamin.tissoires@redhat.com>,
Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Subject: Re: [PATCH] usb: gadget: function: printer: Replace strlcpy with strscpy
Date: Wed, 14 Jun 2023 10:51:01 -0700 [thread overview]
Message-ID: <202306141049.BF86FA8F1F@keescook> (raw)
In-Reply-To: <CADmuW3VEiseKt2UM9o9jzzR8nEawh1jxANyxdZcxk89U65pXEQ@mail.gmail.com>
On Wed, Jun 14, 2023 at 10:12:14AM -0400, Azeem Shaikh wrote:
> On Tue, Jun 13, 2023 at 3:30 PM Kees Cook <keescook@chromium.org> wrote:
> >
> > On Tue, Jun 13, 2023 at 12:43:41AM +0000, Azeem Shaikh wrote:
> [...]
> > > - result = strlcpy(page, opts->pnp_string, PAGE_SIZE);
> > > - if (result >= PAGE_SIZE) {
> > > + result = strscpy(page, opts->pnp_string, PAGE_SIZE);
> > > + if (result == -E2BIG) {
> >
> > I think "< 1" might be a better test here.
>
> Curious, why "< 1" instead of "< 0"?
>
> > > result = PAGE_SIZE;
> > > } else if (page[result - 1] != '\n' && result + 1 < PAGE_SIZE) {
It's for this case above where "result" may be used in an array index,
and if it's 0 or less, there will be a negative array index (due to the "-
1"). So, here, it needs to be "< 1" instead of the more traditional "< 0".
--
Kees Cook
next prev parent reply other threads:[~2023-06-14 17:51 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-13 0:43 [PATCH] usb: gadget: function: printer: Replace strlcpy with strscpy Azeem Shaikh
2023-06-13 19:30 ` Kees Cook
2023-06-14 14:12 ` Azeem Shaikh
2023-06-14 17:51 ` Kees Cook [this message]
2023-06-15 18:09 ` Azeem Shaikh
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