[PATCH v2 1/2] kgdboc: Passing ekgdboc to command line causes panic

[PATCH v2 1/2] kgdboc: Passing ekgdboc to command line causes panic

[zhe.he]

From: He Zhe <zhe.he@windriver.com>

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 <zhe.he@windriver.com>
---
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");
+		return -EINVAL;
+	}
+
 	if (strlen(opt) >= MAX_CONFIG_LEN) {
 		printk(KERN_ERR "kgdboc: config string too long\n");
 		return -ENOSPC;
-- 
2.7.4

[PATCH v2 2/2] kgdboc: Change printk to the right fashion

[zhe.he]

From: He Zhe <zhe.he@windriver.com>

pr_* is preferred according to scripts/checkpatch.pl.

Cc: stable@vger.kernel.org
Signed-off-by: He Zhe <zhe.he@windriver.com>
---
v2:
- Split printk cleanups into a single patch
- Add cc to stable@vger.kernel.org

 drivers/tty/serial/kgdboc.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
index 206f8c2..0003d6c 100644
--- a/drivers/tty/serial/kgdboc.c
+++ b/drivers/tty/serial/kgdboc.c
@@ -136,7 +136,7 @@ static int kgdboc_option_setup(char *opt)
 	}
 
 	if (strlen(opt) >= MAX_CONFIG_LEN) {
-		printk(KERN_ERR "kgdboc: config string too long\n");
+		pr_err("kgdboc: config string too long\n");
 		return -ENOSPC;
 	}
 	strcpy(config, opt);
@@ -253,7 +253,7 @@ static int param_set_kgdboc_var(const char *kmessage,
 	int len = strlen(kmessage);
 
 	if (len >= MAX_CONFIG_LEN) {
-		printk(KERN_ERR "kgdboc: config string too long\n");
+		pr_err("kgdboc: config string too long\n");
 		return -ENOSPC;
 	}
 
@@ -264,8 +264,7 @@ static int param_set_kgdboc_var(const char *kmessage,
 	}
 
 	if (kgdb_connected) {
-		printk(KERN_ERR
-		       "kgdboc: Cannot reconfigure while KGDB is connected.\n");
+		pr_err("kgdboc: Cannot reconfigure while KGDB is connected.\n");
 
 		return -EBUSY;
 	}
-- 
2.7.4

Re: [PATCH v2 1/2] kgdboc: Passing ekgdboc to command line causes panic

[Daniel Thompson]

On Tue, Aug 14, 2018 at 08:46:00PM +0800, zhe.he@windriver.com wrote:
> From: He Zhe <zhe.he@windriver.com>
> 
> 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 <zhe.he@windriver.com>
> ---
> 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.thompson@linaro.org>


Daniel.


> +		return -EINVAL;
> +	}
> +
>  	if (strlen(opt) >= MAX_CONFIG_LEN) {
>  		printk(KERN_ERR "kgdboc: config string too long\n");
>  		return -ENOSPC;
> -- 
> 2.7.4
> 

Re: [PATCH v2 2/2] kgdboc: Change printk to the right fashion

[Daniel Thompson]

On Tue, Aug 14, 2018 at 08:46:01PM +0800, zhe.he@windriver.com wrote:
> From: He Zhe <zhe.he@windriver.com>
> 
> pr_* is preferred according to scripts/checkpatch.pl.
> 
> Cc: stable@vger.kernel.org

This change does not "fix a problem that causes a build error
(but not for things marked CONFIG_BROKEN), an oops, a hang, data
corruption, a real security issue, or some “oh, that’s not good” issue.
In short, something critical.". Only the first patch meets this criteria
and only that patch should be Cc:ed to stable@ .

Please remove from this patch.


> Signed-off-by: He Zhe <zhe.he@windriver.com>
> ---
> v2:
> - Split printk cleanups into a single patch
> - Add cc to stable@vger.kernel.org
> 
>  drivers/tty/serial/kgdboc.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
> index 206f8c2..0003d6c 100644
> --- a/drivers/tty/serial/kgdboc.c
> +++ b/drivers/tty/serial/kgdboc.c
> @@ -136,7 +136,7 @@ static int kgdboc_option_setup(char *opt)
>  	}
>  
>  	if (strlen(opt) >= MAX_CONFIG_LEN) {
> -		printk(KERN_ERR "kgdboc: config string too long\n");
> +		pr_err("kgdboc: config string too long\n");

Looks like you should remove the tags from pr_err and use pr_fmt(fmt) to
put tags on the messages:

#define pr_fmt(fmt) "kgdboc: " fmt


Daniel.

>  		return -ENOSPC;
>  	}
>  	strcpy(config, opt);
> @@ -253,7 +253,7 @@ static int param_set_kgdboc_var(const char *kmessage,
>  	int len = strlen(kmessage);
>  
>  	if (len >= MAX_CONFIG_LEN) {
> -		printk(KERN_ERR "kgdboc: config string too long\n");
> +		pr_err("kgdboc: config string too long\n");
>  		return -ENOSPC;
>  	}
>  
> @@ -264,8 +264,7 @@ static int param_set_kgdboc_var(const char *kmessage,
>  	}
>  
>  	if (kgdb_connected) {
> -		printk(KERN_ERR
> -		       "kgdboc: Cannot reconfigure while KGDB is connected.\n");
> +		pr_err("kgdboc: Cannot reconfigure while KGDB is connected.\n");
>  
>  		return -EBUSY;
>  	}
> -- 
> 2.7.4
> 

Re: [PATCH v2 2/2] kgdboc: Change printk to the right fashion

[Joe Perches]

On Tue, 2018-08-14 at 14:35 +0100, Daniel Thompson wrote:
> On Tue, Aug 14, 2018 at 08:46:01PM +0800, zhe.he@windriver.com wrote:
> > From: He Zhe <zhe.he@windriver.com>
> > 
> > pr_* is preferred according to scripts/checkpatch.pl.
[]
> > diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
[]
> > @@ -136,7 +136,7 @@ static int kgdboc_option_setup(char *opt)
> >  	}
> >  
> >  	if (strlen(opt) >= MAX_CONFIG_LEN) {
> > -		printk(KERN_ERR "kgdboc: config string too long\n");
> > +		pr_err("kgdboc: config string too long\n");
> 
> Looks like you should remove the tags from pr_err and use pr_fmt(fmt) to
> put tags on the messages:
> 
> #define pr_fmt(fmt) "kgdboc: " fmt

True and it's probably better to use:

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

Re: [PATCH v2 2/2] kgdboc: Change printk to the right fashion

[Daniel Thompson]

On Tue, Aug 14, 2018 at 07:04:11AM -0700, Joe Perches wrote:
> On Tue, 2018-08-14 at 14:35 +0100, Daniel Thompson wrote:
> > On Tue, Aug 14, 2018 at 08:46:01PM +0800, zhe.he@windriver.com wrote:
> > > From: He Zhe <zhe.he@windriver.com>
> > > 
> > > pr_* is preferred according to scripts/checkpatch.pl.
> []
> > > diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
> []
> > > @@ -136,7 +136,7 @@ static int kgdboc_option_setup(char *opt)
> > >  	}
> > >  
> > >  	if (strlen(opt) >= MAX_CONFIG_LEN) {
> > > -		printk(KERN_ERR "kgdboc: config string too long\n");
> > > +		pr_err("kgdboc: config string too long\n");
> > 
> > Looks like you should remove the tags from pr_err and use pr_fmt(fmt) to
> > put tags on the messages:
> > 
> > #define pr_fmt(fmt) "kgdboc: " fmt
> 
> True and it's probably better to use:
> 
> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

Good point! Thanks.


Daniel.

Re: [PATCH v2 2/2] kgdboc: Change printk to the right fashion

[He Zhe]

On 2018年08月14日 22:41, Daniel Thompson wrote:
> On Tue, Aug 14, 2018 at 07:04:11AM -0700, Joe Perches wrote:
>> On Tue, 2018-08-14 at 14:35 +0100, Daniel Thompson wrote:
>>> On Tue, Aug 14, 2018 at 08:46:01PM +0800, zhe.he@windriver.com wrote:
>>>> From: He Zhe <zhe.he@windriver.com>
>>>>
>>>> pr_* is preferred according to scripts/checkpatch.pl.
>> []
>>>> diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
>> []
>>>> @@ -136,7 +136,7 @@ static int kgdboc_option_setup(char *opt)
>>>>  	}
>>>>  
>>>>  	if (strlen(opt) >= MAX_CONFIG_LEN) {
>>>> -		printk(KERN_ERR "kgdboc: config string too long\n");
>>>> +		pr_err("kgdboc: config string too long\n");
>>> Looks like you should remove the tags from pr_err and use pr_fmt(fmt) to
>>> put tags on the messages:
>>>
>>> #define pr_fmt(fmt) "kgdboc: " fmt
>> True and it's probably better to use:
>>
>> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> Good point! Thanks.

Daniel, Joe, thanks for your good suggestions. v3 is sent.

Zhe

>
>
> Daniel.
>