Re: [PATCH] CIFS: Fix a potencially linear read overflow

From: Paulo Alcantara <pc@cjr.nz>
To: Len Baker <len.baker@gmx.com>, Steve French <sfrench@samba.org>,
	Jeff Layton <jlayton@kernel.org>,
	Suresh Jayaraman <sjayaraman@suse.de>
Cc: Len Baker <len.baker@gmx.com>,
	linux-cifs@vger.kernel.org, samba-technical@lists.samba.org,
	linux-kernel@vger.kernel.org, Kees Cook <keescook@chromium.org>,
	linux-hardening@vger.kernel.org
Subject: Re: [PATCH] CIFS: Fix a potencially linear read overflow
Date: Tue, 17 Aug 2021 21:28:40 -0300	[thread overview]
Message-ID: <87im03h9zb.fsf@cjr.nz> (raw)
In-Reply-To: <20210817102709.15046-1-len.baker@gmx.com>

Len Baker <len.baker@gmx.com> writes:

> strlcpy() reads the entire source buffer first. This read may exceed the
> destination size limit. This is both inefficient and can lead to linear
> read overflows if a source string is not NUL-terminated.
>
> Also, the strnlen() call does not avoid the read overflow in the strlcpy
> function when a not NUL-terminated string is passed.
>
> So, replace this block by a call to kstrndup() that avoids this type of
> overflow and does the same.
>
> Fixes: 066ce6899484d ("cifs: rename cifs_strlcpy_to_host and make it use new functions")
> Signed-off-by: Len Baker <len.baker@gmx.com>
> ---
>  fs/cifs/cifs_unicode.c | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)

Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>