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[86.9.19.6]) by smtp.gmail.com with ESMTPSA id f17-v6sm14592819wrs.1.2018.08.14.06.27.00 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 14 Aug 2018 06:27:00 -0700 (PDT) Date: Tue, 14 Aug 2018 14:26:58 +0100 From: Daniel Thompson To: zhe.he@windriver.com Cc: jason.wessel@windriver.com, gregkh@linuxfoundation.org, jslaby@suse.com, kgdb-bugreport@lists.sourceforge.net, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] kgdboc: Passing ekgdboc to command line causes panic Message-ID: <20180814132658.nadasqcwi3f44duv@holly.lan> References: <1534250761-824-1-git-send-email-zhe.he@windriver.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1534250761-824-1-git-send-email-zhe.he@windriver.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 14, 2018 at 08:46:00PM +0800, zhe.he@windriver.com wrote: > From: He Zhe > > kgdboc_option_setup does not check input argument before passing it > to strlen. The argument would be a NULL pointer if "ekgdboc", without > its value, is set in command line and thus cause the following panic. > > PANIC: early exception 0xe3 IP 10:ffffffff8fbbb620 error 0 cr2 0x0 > [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.18-rc8+ #1 > [ 0.000000] RIP: 0010:strlen+0x0/0x20 > ... > [ 0.000000] Call Trace > [ 0.000000] ? kgdboc_option_setup+0x9/0xa0 > [ 0.000000] ? kgdboc_early_init+0x6/0x1b > [ 0.000000] ? do_early_param+0x4d/0x82 > [ 0.000000] ? parse_args+0x212/0x330 > [ 0.000000] ? rdinit_setup+0x26/0x26 > [ 0.000000] ? parse_early_options+0x20/0x23 > [ 0.000000] ? rdinit_setup+0x26/0x26 > [ 0.000000] ? parse_early_param+0x2d/0x39 > [ 0.000000] ? setup_arch+0x2f7/0xbf4 > [ 0.000000] ? start_kernel+0x5e/0x4c2 > [ 0.000000] ? load_ucode_bsp+0x113/0x12f > [ 0.000000] ? secondary_startup_64+0xa5/0xb0 > > This patch adds a check to prevent the panic. > > Cc: stable@vger.kernel.org > Signed-off-by: He Zhe > --- > v2: > - Split out printk cleanups > - Add cc to stable@vger.kernel.org > > drivers/tty/serial/kgdboc.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c > index b4ba2b1..206f8c2 100644 > --- a/drivers/tty/serial/kgdboc.c > +++ b/drivers/tty/serial/kgdboc.c > @@ -130,6 +130,11 @@ static void kgdboc_unregister_kbd(void) > > static int kgdboc_option_setup(char *opt) > { > + if (!opt) { > + pr_err("kgdboc: null option\n"); Apologies... I should have picked this up when I replied earlier but this error message describes what the function gets when I think it should report what the user actually did. So should be something like: pr_err("kgdboc: config string not provided\n"); With that (or a very similar) change: Reviewed-by: Daniel Thompson Daniel. > + return -EINVAL; > + } > + > if (strlen(opt) >= MAX_CONFIG_LEN) { > printk(KERN_ERR "kgdboc: config string too long\n"); > return -ENOSPC; > -- > 2.7.4 >