brd: check parameter validation before register_blkdev func
diff mbox series

Message ID 342ee238-0e7c-c213-eecc-7062f24985cc@huawei.com
State New
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Series
  • brd: check parameter validation before register_blkdev func
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Commit Message

Zhiqiang Liu Jan. 10, 2020, 5:10 a.m. UTC
In brd_init func, rd_nr num of brd_device are firstly allocated
and add in brd_devices, then brd_devices are traversed to add each
brd_device by calling add_disk func. When allocating brd_device,
the disk->first_minor is set to i * max_part, if rd_nr * max_part
is larger than MINORMASK, two different brd_device may have the same
devt, then only one of them can be successfully added.
when rmmod brd.ko, it will cause oops when calling brd_exit.

Follow those steps:
  # modprobe brd rd_nr=3 rd_size=102400 max_part=1048576
  # rmmod brd
then, the oops will appear.

Oops log:
[  726.613722] Call trace:
[  726.614175]  kernfs_find_ns+0x24/0x130
[  726.614852]  kernfs_find_and_get_ns+0x44/0x68
[  726.615749]  sysfs_remove_group+0x38/0xb0
[  726.616520]  blk_trace_remove_sysfs+0x1c/0x28
[  726.617320]  blk_unregister_queue+0x98/0x100
[  726.618105]  del_gendisk+0x144/0x2b8
[  726.618759]  brd_exit+0x68/0x560 [brd]
[  726.619501]  __arm64_sys_delete_module+0x19c/0x2a0
[  726.620384]  el0_svc_common+0x78/0x130
[  726.621057]  el0_svc_handler+0x38/0x78
[  726.621738]  el0_svc+0x8/0xc
[  726.622259] Code: aa0203f6 aa0103f7 aa1e03e0 d503201f (7940e260)

Here, we add brd_check_par_valid func to check parameter
validation before register_blkdev func.

Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
---
 drivers/block/brd.c | 33 ++++++++++++++++++++++++++-------
 1 file changed, 26 insertions(+), 7 deletions(-)

Comments

Zhiqiang Liu Jan. 13, 2020, 9:55 a.m. UTC | #1
Friendly ping...

On 2020/1/10 13:10, Zhiqiang Liu wrote:
> 
> In brd_init func, rd_nr num of brd_device are firstly allocated
> and add in brd_devices, then brd_devices are traversed to add each
> brd_device by calling add_disk func. When allocating brd_device,
> the disk->first_minor is set to i * max_part, if rd_nr * max_part
> is larger than MINORMASK, two different brd_device may have the same
> devt, then only one of them can be successfully added.
> when rmmod brd.ko, it will cause oops when calling brd_exit.
> 
> Follow those steps:
>   # modprobe brd rd_nr=3 rd_size=102400 max_part=1048576
>   # rmmod brd
> then, the oops will appear.
> 
> Oops log:
> [  726.613722] Call trace:
> [  726.614175]  kernfs_find_ns+0x24/0x130
> [  726.614852]  kernfs_find_and_get_ns+0x44/0x68
> [  726.615749]  sysfs_remove_group+0x38/0xb0
> [  726.616520]  blk_trace_remove_sysfs+0x1c/0x28
> [  726.617320]  blk_unregister_queue+0x98/0x100
> [  726.618105]  del_gendisk+0x144/0x2b8
> [  726.618759]  brd_exit+0x68/0x560 [brd]
> [  726.619501]  __arm64_sys_delete_module+0x19c/0x2a0
> [  726.620384]  el0_svc_common+0x78/0x130
> [  726.621057]  el0_svc_handler+0x38/0x78
> [  726.621738]  el0_svc+0x8/0xc
> [  726.622259] Code: aa0203f6 aa0103f7 aa1e03e0 d503201f (7940e260)
> 
> Here, we add brd_check_par_valid func to check parameter
> validation before register_blkdev func.
> 
> Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
> ---
>  drivers/block/brd.c | 33 ++++++++++++++++++++++++++-------
>  1 file changed, 26 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/block/brd.c b/drivers/block/brd.c
> index df8103dd40ac..3a4510b2c24f 100644
> --- a/drivers/block/brd.c
> +++ b/drivers/block/brd.c
> @@ -330,16 +330,16 @@ static const struct block_device_operations brd_fops = {
>  /*
>   * And now the modules code and kernel interface.
>   */
> -static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT;
> -module_param(rd_nr, int, 0444);
> +static unsigned int rd_nr = CONFIG_BLK_DEV_RAM_COUNT;
> +module_param(rd_nr, uint, 0444);
>  MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");
> 
>  unsigned long rd_size = CONFIG_BLK_DEV_RAM_SIZE;
>  module_param(rd_size, ulong, 0444);
>  MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
> 
> -static int max_part = 1;
> -module_param(max_part, int, 0444);
> +static unsigned int max_part = 1;
> +module_param(max_part, uint, 0444);
>  MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices");
> 
>  MODULE_LICENSE("GPL");
> @@ -468,10 +468,25 @@ static struct kobject *brd_probe(dev_t dev, int *part, void *data)
>  	return kobj;
>  }
> 
> +static inline int brd_check_par_valid(void)
> +{
> +	if (unlikely(!rd_nr))
> +		rd_nr = 1;
> +
> +	if (unlikely(!max_part))
> +		max_part = 1;
> +
> +	if (rd_nr * max_part > MINORMASK)
> +		return -EINVAL;
> +
> +	return 0;
> +
> +}
> +
>  static int __init brd_init(void)
>  {
>  	struct brd_device *brd, *next;
> -	int i;
> +	int i, ret;
> 
>  	/*
>  	 * brd module now has a feature to instantiate underlying device
> @@ -488,11 +503,15 @@ static int __init brd_init(void)
>  	 *	dynamically.
>  	 */
> 
> +	ret = brd_check_par_valid();
> +	if (ret) {
> +		pr_info("brd: invalid parameter setting!!!\n");
> +		return ret;
> +	}
> +
>  	if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))
>  		return -EIO;
> 
> -	if (unlikely(!max_part))
> -		max_part = 1;
> 
>  	for (i = 0; i < rd_nr; i++) {
>  		brd = brd_alloc(i);
>
Ming Lei Jan. 13, 2020, 11:04 a.m. UTC | #2
On Fri, Jan 10, 2020 at 01:10:20PM +0800, Zhiqiang Liu wrote:
> 
> In brd_init func, rd_nr num of brd_device are firstly allocated
> and add in brd_devices, then brd_devices are traversed to add each
> brd_device by calling add_disk func. When allocating brd_device,
> the disk->first_minor is set to i * max_part, if rd_nr * max_part
> is larger than MINORMASK, two different brd_device may have the same
> devt, then only one of them can be successfully added.
> when rmmod brd.ko, it will cause oops when calling brd_exit.
> 
> Follow those steps:
>   # modprobe brd rd_nr=3 rd_size=102400 max_part=1048576
>   # rmmod brd
> then, the oops will appear.
> 
> Oops log:
> [  726.613722] Call trace:
> [  726.614175]  kernfs_find_ns+0x24/0x130
> [  726.614852]  kernfs_find_and_get_ns+0x44/0x68
> [  726.615749]  sysfs_remove_group+0x38/0xb0
> [  726.616520]  blk_trace_remove_sysfs+0x1c/0x28
> [  726.617320]  blk_unregister_queue+0x98/0x100
> [  726.618105]  del_gendisk+0x144/0x2b8
> [  726.618759]  brd_exit+0x68/0x560 [brd]
> [  726.619501]  __arm64_sys_delete_module+0x19c/0x2a0
> [  726.620384]  el0_svc_common+0x78/0x130
> [  726.621057]  el0_svc_handler+0x38/0x78
> [  726.621738]  el0_svc+0x8/0xc
> [  726.622259] Code: aa0203f6 aa0103f7 aa1e03e0 d503201f (7940e260)
> 
> Here, we add brd_check_par_valid func to check parameter
> validation before register_blkdev func.
> 
> Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
> ---
>  drivers/block/brd.c | 33 ++++++++++++++++++++++++++-------
>  1 file changed, 26 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/block/brd.c b/drivers/block/brd.c
> index df8103dd40ac..3a4510b2c24f 100644
> --- a/drivers/block/brd.c
> +++ b/drivers/block/brd.c
> @@ -330,16 +330,16 @@ static const struct block_device_operations brd_fops = {
>  /*
>   * And now the modules code and kernel interface.
>   */
> -static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT;
> -module_param(rd_nr, int, 0444);
> +static unsigned int rd_nr = CONFIG_BLK_DEV_RAM_COUNT;
> +module_param(rd_nr, uint, 0444);
>  MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");
> 
>  unsigned long rd_size = CONFIG_BLK_DEV_RAM_SIZE;
>  module_param(rd_size, ulong, 0444);
>  MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");
> 
> -static int max_part = 1;
> -module_param(max_part, int, 0444);
> +static unsigned int max_part = 1;
> +module_param(max_part, uint, 0444);
>  MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices");
> 
>  MODULE_LICENSE("GPL");
> @@ -468,10 +468,25 @@ static struct kobject *brd_probe(dev_t dev, int *part, void *data)
>  	return kobj;
>  }
> 
> +static inline int brd_check_par_valid(void)
> +{
> +	if (unlikely(!rd_nr))
> +		rd_nr = 1;
> +
> +	if (unlikely(!max_part))
> +		max_part = 1;
> +
> +	if (rd_nr * max_part > MINORMASK)
> +		return -EINVAL;
> +
> +	return 0;
> +
> +}
> +
>  static int __init brd_init(void)
>  {
>  	struct brd_device *brd, *next;
> -	int i;
> +	int i, ret;
> 
>  	/*
>  	 * brd module now has a feature to instantiate underlying device
> @@ -488,11 +503,15 @@ static int __init brd_init(void)
>  	 *	dynamically.
>  	 */
> 
> +	ret = brd_check_par_valid();
> +	if (ret) {
> +		pr_info("brd: invalid parameter setting!!!\n");
> +		return ret;
> +	}
> +

The max supported partition number is 256, see __alloc_disk_node().
So even though one bigger number is passed to alloc_disk(), at most
256 partitions are allowed on that disk. Maybe you can apply the
following way to avoid the issue:

	disk->first_minor       = i * disk->minors;

However, looks 'rd_nr' still needs to be validated(rd_nr < 2 ^ 23).

Thanks,
Ming
Zhiqiang Liu Jan. 13, 2020, 12:55 p.m. UTC | #3
On 2020/1/13 19:04, Ming Lei wrote:
> On Fri, Jan 10, 2020 at 01:10:20PM +0800, Zhiqiang Liu wrote:
>>
>> In brd_init func, rd_nr num of brd_device are firstly allocated
>> and add in brd_devices, then brd_devices are traversed to add each
>> brd_device by calling add_disk func. When allocating brd_device,
>> the disk->first_minor is set to i * max_part, if rd_nr * max_part
>> is larger than MINORMASK, two different brd_device may have the same
>> devt, then only one of them can be successfully added.
>> when rmmod brd.ko, it will cause oops when calling brd_exit.
>>
>> Follow those steps:
>>   # modprobe brd rd_nr=3 rd_size=102400 max_part=1048576
>>   # rmmod brd
>> then, the oops will appear.
>>
>> Oops log:
>> [  726.613722] Call trace:
>> [  726.614175]  kernfs_find_ns+0x24/0x130
>> [  726.614852]  kernfs_find_and_get_ns+0x44/0x68
>> [  726.615749]  sysfs_remove_group+0x38/0xb0
>> [  726.616520]  blk_trace_remove_sysfs+0x1c/0x28
>> [  726.617320]  blk_unregister_queue+0x98/0x100
>> [  726.618105]  del_gendisk+0x144/0x2b8
>> [  726.618759]  brd_exit+0x68/0x560 [brd]
>> [  726.619501]  __arm64_sys_delete_module+0x19c/0x2a0
>> [  726.620384]  el0_svc_common+0x78/0x130
>> [  726.621057]  el0_svc_handler+0x38/0x78
>> [  726.621738]  el0_svc+0x8/0xc
>> [  726.622259] Code: aa0203f6 aa0103f7 aa1e03e0 d503201f (7940e260)
>>
>> Here, we add brd_check_par_valid func to check parameter
>> validation before register_blkdev func.
>>
>> Signed-off-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
>> ---
>>  drivers/block/brd.c | 33 ++++++++++++++++++++++++++-------
>> +static inline int brd_check_par_valid(void)
>> +{
>> +	if (unlikely(!rd_nr))
>> +		rd_nr = 1;
>> +
>> +	if (unlikely(!max_part))
>> +		max_part = 1;
>> +
>> +	if (rd_nr * max_part > MINORMASK)
>> +		return -EINVAL;
>> +
>> +	return 0;
>> +
>> +}
>> +
>>  static int __init brd_init(void)
>>  {
>>  	struct brd_device *brd, *next;
>> -	int i;
>> +	int i, ret;
>>
>>  	/*
>>  	 * brd module now has a feature to instantiate underlying device
>> @@ -488,11 +503,15 @@ static int __init brd_init(void)
>>  	 *	dynamically.
>>  	 */
>>
>> +	ret = brd_check_par_valid();
>> +	if (ret) {
>> +		pr_info("brd: invalid parameter setting!!!\n");
>> +		return ret;
>> +	}
>> +
> 
> The max supported partition number is 256, see __alloc_disk_node().
> So even though one bigger number is passed to alloc_disk(), at most
> 256 partitions are allowed on that disk. Maybe you can apply the
> following way to avoid the issue:
> 
> 	disk->first_minor       = i * disk->minors;
> 
> However, looks 'rd_nr' still needs to be validated(rd_nr < 2 ^ 23).
> 

Thanks for your reply.
As you said, minors is limited to DISK_MAX_PARTS in __alloc_disk_node when
calling alloc_disk in brd_alloc func. We can set: disk->first_minor = i * disk->minors
as your suggestion.
As for 'rd_nr', I think we should make sure that 'disk->first_minor' should be not
larger than MINORMASK.

->add_disk
  ->device_add_disk
    ->__device_add_disk
      ->blk_alloc_devt
	->MKDEV

If rd_nr > MINORMASK / min(max_part, DISK_MAX_PARTS), two different brd_device may have the same devt
by calling MKDEV in blk_alloc_devt func. For example, MKDEV(1, 0) is equal to MKDEV(1, MINORMASK + 1).
So we should check both rd_nr and max_part as follows,

    static inline int brd_check_par_valid(void)
    {
            if (unlikely(!rd_nr))
                    rd_nr = 1;

            if (unlikely(!max_part))
                    max_part = 1;

            if (max_part > DISK_MAX_PARTS)
                    max_part = DISK_MAX_PARTS;

            if (rd_nr > MINORMASK / max_part)
                    return -EINVAL;

            return 0;
    }

I will send the v2 patch.

Patch
diff mbox series

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index df8103dd40ac..3a4510b2c24f 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -330,16 +330,16 @@  static const struct block_device_operations brd_fops = {
 /*
  * And now the modules code and kernel interface.
  */
-static int rd_nr = CONFIG_BLK_DEV_RAM_COUNT;
-module_param(rd_nr, int, 0444);
+static unsigned int rd_nr = CONFIG_BLK_DEV_RAM_COUNT;
+module_param(rd_nr, uint, 0444);
 MODULE_PARM_DESC(rd_nr, "Maximum number of brd devices");

 unsigned long rd_size = CONFIG_BLK_DEV_RAM_SIZE;
 module_param(rd_size, ulong, 0444);
 MODULE_PARM_DESC(rd_size, "Size of each RAM disk in kbytes.");

-static int max_part = 1;
-module_param(max_part, int, 0444);
+static unsigned int max_part = 1;
+module_param(max_part, uint, 0444);
 MODULE_PARM_DESC(max_part, "Num Minors to reserve between devices");

 MODULE_LICENSE("GPL");
@@ -468,10 +468,25 @@  static struct kobject *brd_probe(dev_t dev, int *part, void *data)
 	return kobj;
 }

+static inline int brd_check_par_valid(void)
+{
+	if (unlikely(!rd_nr))
+		rd_nr = 1;
+
+	if (unlikely(!max_part))
+		max_part = 1;
+
+	if (rd_nr * max_part > MINORMASK)
+		return -EINVAL;
+
+	return 0;
+
+}
+
 static int __init brd_init(void)
 {
 	struct brd_device *brd, *next;
-	int i;
+	int i, ret;

 	/*
 	 * brd module now has a feature to instantiate underlying device
@@ -488,11 +503,15 @@  static int __init brd_init(void)
 	 *	dynamically.
 	 */

+	ret = brd_check_par_valid();
+	if (ret) {
+		pr_info("brd: invalid parameter setting!!!\n");
+		return ret;
+	}
+
 	if (register_blkdev(RAMDISK_MAJOR, "ramdisk"))
 		return -EIO;

-	if (unlikely(!max_part))
-		max_part = 1;

 	for (i = 0; i < rd_nr; i++) {
 		brd = brd_alloc(i);