[PATCH V3] staging: dgap: implement error handling in dgap_tty_register()

[PATCH V3] staging: dgap: implement error handling in dgap_tty_register()

[Daeseok Youn]

- alloc_tty_driver() is deprecated so it is changed to
tty_alloc_driver()
- Pointers which are allocated by alloc_tty_driver() and kzalloc()
can be NULL so it need to check NULL for them.
- If one of those is failed, it need to add proper handler for
avoiding memory leak.
- If both of drivers are registered normally, and
then set TRUE to dgap_major_serial{print}_registered. If one
of drivers is failed to register, leave a default value as
FALSE.

Signed-off-by: Daeseok Youn <daeseok.youn@gmail.com>
---
V2: rebased on staging-next branch
V3: removes unneeded information in e-mail

 drivers/staging/dgap/dgap.c |   49 +++++++++++++++++++++++++++++++++---------
 1 files changed, 38 insertions(+), 11 deletions(-)

diff --git a/drivers/staging/dgap/dgap.c b/drivers/staging/dgap/dgap.c
index d7cfc45..e4cb7aa 100644
--- a/drivers/staging/dgap/dgap.c
+++ b/drivers/staging/dgap/dgap.c
@@ -1212,7 +1212,9 @@ static int dgap_tty_register(struct board_t *brd)
 {
 	int rc = 0;
 
-	brd->serial_driver = alloc_tty_driver(MAXPORTS);
+	brd->serial_driver = tty_alloc_driver(MAXPORTS, 0);
+	if (IS_ERR(brd->serial_driver))
+		return PTR_ERR(brd->serial_driver);
 
 	snprintf(brd->serial_name, MAXTTYNAMELEN, "tty_dgap_%d_",
 		 brd->boardnum);
@@ -1231,8 +1233,10 @@ static int dgap_tty_register(struct board_t *brd)
 	/* The kernel wants space to store pointers to tty_structs */
 	brd->serial_driver->ttys =
 		kzalloc(MAXPORTS * sizeof(struct tty_struct *), GFP_KERNEL);
-	if (!brd->serial_driver->ttys)
-		return -ENOMEM;
+	if (!brd->serial_driver->ttys) {
+		rc = -ENOMEM;
+		goto free_serial_drv;
+	}
 
 	/*
 	 * Entry points for driver.  Called by the kernel from
@@ -1245,7 +1249,11 @@ static int dgap_tty_register(struct board_t *brd)
 	 * again, separately so we don't get the LD confused about what major
 	 * we are when we get into the dgap_tty_open() routine.
 	 */
-	brd->print_driver = alloc_tty_driver(MAXPORTS);
+	brd->print_driver = tty_alloc_driver(MAXPORTS, 0);
+	if (IS_ERR(brd->print_driver)) {
+		rc = PTR_ERR(brd->print_driver);
+		goto free_serial_ttys;
+	}
 
 	snprintf(brd->print_name, MAXTTYNAMELEN, "pr_dgap_%d_",
 		 brd->boardnum);
@@ -1264,8 +1272,10 @@ static int dgap_tty_register(struct board_t *brd)
 	/* The kernel wants space to store pointers to tty_structs */
 	brd->print_driver->ttys =
 		kzalloc(MAXPORTS * sizeof(struct tty_struct *), GFP_KERNEL);
-	if (!brd->print_driver->ttys)
-		return -ENOMEM;
+	if (!brd->print_driver->ttys) {
+		rc = -ENOMEM;
+		goto free_print_drv;
+	}
 
 	/*
 	 * Entry points for driver.  Called by the kernel from
@@ -1276,20 +1286,37 @@ static int dgap_tty_register(struct board_t *brd)
 	/* Register tty devices */
 	rc = tty_register_driver(brd->serial_driver);
 	if (rc < 0)
-		return rc;
-	brd->dgap_major_serial_registered = TRUE;
-	dgap_boards_by_major[brd->serial_driver->major] = brd;
-	brd->dgap_serial_major = brd->serial_driver->major;
+		goto free_print_ttys;
 
 	/* Register Transparent Print devices */
 	rc = tty_register_driver(brd->print_driver);
 	if (rc < 0)
-		return rc;
+		goto unregister_serial_drv;
+
+	brd->dgap_major_serial_registered = TRUE;
+	dgap_boards_by_major[brd->serial_driver->major] = brd;
+	brd->dgap_serial_major = brd->serial_driver->major;
+
 	brd->dgap_major_transparent_print_registered = TRUE;
 	dgap_boards_by_major[brd->print_driver->major] = brd;
 	brd->dgap_transparent_print_major = brd->print_driver->major;
 
 	return rc;
+
+unregister_serial_drv:
+	tty_unregister_driver(brd->serial_driver);
+free_print_ttys:
+	kfree(brd->print_driver->ttys);
+	brd->print_driver->ttys = NULL;
+free_print_drv:
+	put_tty_driver(brd->print_driver);
+free_serial_ttys:
+	kfree(brd->serial_driver->ttys);
+	brd->serial_driver->ttys = NULL;
+free_serial_drv:
+	put_tty_driver(brd->serial_driver);
+
+	return rc;
 }
 
 /*
-- 
1.7.1

Re: [PATCH V3] staging: dgap: implement error handling in dgap_tty_register()

[Dan Carpenter]

Nice, but it needs a couple style improvements below.

On Mon, May 19, 2014 at 11:10:30AM +0900, Daeseok Youn wrote:
> +	brd->dgap_major_serial_registered = TRUE;
> +	dgap_boards_by_major[brd->serial_driver->major] = brd;
> +	brd->dgap_serial_major = brd->serial_driver->major;
> +
>  	brd->dgap_major_transparent_print_registered = TRUE;
>  	dgap_boards_by_major[brd->print_driver->major] = brd;
>  	brd->dgap_transparent_print_major = brd->print_driver->major;
>  
>  	return rc;

	return 0;

> +
> +unregister_serial_drv:
> +	tty_unregister_driver(brd->serial_driver);
> +free_print_ttys:
> +	kfree(brd->print_driver->ttys);
> +	brd->print_driver->ttys = NULL;

This label isn't needed.  Just goto free_print_drv, because that will
free the brd->print_driver->ttys in destruct_tty_driver().
I do like how you noticed the double free and avoided it by setting
brd->serial_driver->ttys to NULL, so your patch doesn't introduce a
double free bug.

> +free_print_drv:
> +	put_tty_driver(brd->print_driver);
> +free_serial_ttys:
> +	kfree(brd->serial_driver->ttys);
> +	brd->serial_driver->ttys = NULL;

Same for this.

> +free_serial_drv:
> +	put_tty_driver(brd->serial_driver);
> +
> +	return rc;

regards,
dan carpenter

Re: [PATCH V3] staging: dgap: implement error handling in dgap_tty_register()

[Dan Carpenter]

On Mon, May 19, 2014 at 11:10:30AM +0900, Daeseok Youn wrote:
> diff --git a/drivers/staging/dgap/dgap.c b/drivers/staging/dgap/dgap.c
> index d7cfc45..e4cb7aa 100644
> --- a/drivers/staging/dgap/dgap.c
> +++ b/drivers/staging/dgap/dgap.c
> @@ -1212,7 +1212,9 @@ static int dgap_tty_register(struct board_t *brd)
>  {
>  	int rc = 0;

Oh, and you may as well remove this initialization while you are at it.

regards,
dan carpenter

Re: [PATCH V3] staging: dgap: implement error handling in dgap_tty_register()

[DaeSeok Youn]

2014-05-19 17:02 GMT+09:00 Dan Carpenter <dan.carpenter@oracle.com>:
> Nice, but it needs a couple style improvements below.
>
> On Mon, May 19, 2014 at 11:10:30AM +0900, Daeseok Youn wrote:
>> +     brd->dgap_major_serial_registered = TRUE;
>> +     dgap_boards_by_major[brd->serial_driver->major] = brd;
>> +     brd->dgap_serial_major = brd->serial_driver->major;
>> +
>>       brd->dgap_major_transparent_print_registered = TRUE;
>>       dgap_boards_by_major[brd->print_driver->major] = brd;
>>       brd->dgap_transparent_print_major = brd->print_driver->major;
>>
>>       return rc;
>
>         return 0;
OK. I will remove "int rc = 0" line and change "return rc" to "return 0"

>
>> +
>> +unregister_serial_drv:
>> +     tty_unregister_driver(brd->serial_driver);
>> +free_print_ttys:
>> +     kfree(brd->print_driver->ttys);
>> +     brd->print_driver->ttys = NULL;
>
> This label isn't needed.  Just goto free_print_drv, because that will
> free the brd->print_driver->ttys in destruct_tty_driver().
> I do like how you noticed the double free and avoided it by setting
> brd->serial_driver->ttys to NULL, so your patch doesn't introduce a
> double free bug.
Yes, just goto free_print_drv.

Thanks for review.

Regards,
Daeseok Youn
>
>> +free_print_drv:
>> +     put_tty_driver(brd->print_driver);
>> +free_serial_ttys:
>> +     kfree(brd->serial_driver->ttys);
>> +     brd->serial_driver->ttys = NULL;
>
> Same for this.
>
>> +free_serial_drv:
>> +     put_tty_driver(brd->serial_driver);
>> +
>> +     return rc;
>
> regards,
> dan carpenter

Re: [PATCH V3] staging: dgap: implement error handling in dgap_tty_register()

[DaeSeok Youn]

2014-05-19 18:39 GMT+09:00 DaeSeok Youn <daeseok.youn@gmail.com>:
> 2014-05-19 17:02 GMT+09:00 Dan Carpenter <dan.carpenter@oracle.com>:
>> Nice, but it needs a couple style improvements below.
>>
>> On Mon, May 19, 2014 at 11:10:30AM +0900, Daeseok Youn wrote:
>>> +     brd->dgap_major_serial_registered = TRUE;
>>> +     dgap_boards_by_major[brd->serial_driver->major] = brd;
>>> +     brd->dgap_serial_major = brd->serial_driver->major;
>>> +
>>>       brd->dgap_major_transparent_print_registered = TRUE;
>>>       dgap_boards_by_major[brd->print_driver->major] = brd;
>>>       brd->dgap_transparent_print_major = brd->print_driver->major;
>>>
>>>       return rc;
>>
>>         return 0;
> OK. I will remove "int rc = 0" line and change "return rc" to "return 0"
Oh.. just remove the initialization to zero.
>
>>
>>> +
>>> +unregister_serial_drv:
>>> +     tty_unregister_driver(brd->serial_driver);
>>> +free_print_ttys:
>>> +     kfree(brd->print_driver->ttys);
>>> +     brd->print_driver->ttys = NULL;
>>
>> This label isn't needed.  Just goto free_print_drv, because that will
>> free the brd->print_driver->ttys in destruct_tty_driver().
>> I do like how you noticed the double free and avoided it by setting
>> brd->serial_driver->ttys to NULL, so your patch doesn't introduce a
>> double free bug.
> Yes, just goto free_print_drv.
>
> Thanks for review.
>
> Regards,
> Daeseok Youn
>>
>>> +free_print_drv:
>>> +     put_tty_driver(brd->print_driver);
>>> +free_serial_ttys:
>>> +     kfree(brd->serial_driver->ttys);
>>> +     brd->serial_driver->ttys = NULL;
>>
>> Same for this.
>>
>>> +free_serial_drv:
>>> +     put_tty_driver(brd->serial_driver);
>>> +
>>> +     return rc;
>>
>> regards,
>> dan carpenter