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Message-ID: <e5807f3c-3173-44e6-b222-fc4679be4680@linux.dev>
Date: Wed, 18 Sep 2024 10:57:10 +0800
From: Zhu Yanjun <yanjun.zhu@...ux.dev>
To: Yu Kuai <yukuai1@...weicloud.com>, Damien Le Moal <dlemoal@...nel.org>,
Aleksandr Mishin <amishin@...rgos.ru>, Shaohua Li <shli@...com>
Cc: Jens Axboe <axboe@...nel.dk>, Hannes Reinecke <hare@...e.de>,
Johannes Thumshirn <johannes.thumshirn@....com>,
Chaitanya Kulkarni <kch@...dia.com>,
Chengming Zhou <zhouchengming@...edance.com>,
John Garry <john.g.garry@...cle.com>,
Shin'ichiro Kawasaki <shinichiro.kawasaki@....com>,
linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
lvc-project@...uxtesting.org, "yukuai (C)" <yukuai3@...wei.com>,
"yangerkun@...wei.com" <yangerkun@...wei.com>
Subject: Re: [PATCH] nullb: Adjust device size calculation in null_alloc_dev()
在 2024/9/18 10:07, Yu Kuai 写道:
>
>
> 在 2024/09/18 0:29, Zhu Yanjun 写道:
>> 在 2024/9/17 15:24, Damien Le Moal 写道:
>>> On 2024/09/17 16:21, Damien Le Moal wrote:
>>>> On 2024/09/17 16:07, Aleksandr Mishin wrote:
>>>>> In null_alloc_dev() device size is a subject to overflow because
>>>>> 'g_gb'
>>>>> (which is module parameter, may have any value and is not validated
>>>>> anywhere) is not cast to a larger data type before performing
>>>>> arithmetic.
>>>>>
>>>>> Cast 'g_gb' to unsigned long to prevent overflow.
>>>>>
>>>>> Found by Linux Verification Center (linuxtesting.org) with SVACE.
>>>>>
>>>>> Fixes: 2984c8684f96 ("nullb: factor disk parameters")
>>>>> Signed-off-by: Aleksandr Mishin <amishin@...rgos.ru>
>>>>> ---
>>>>> drivers/block/null_blk/main.c | 2 +-
>>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/block/null_blk/main.c
>>>>> b/drivers/block/null_blk/main.c
>>>>> index 2f0431e42c49..5edbf9c0aceb 100644
>>>>> --- a/drivers/block/null_blk/main.c
>>>>> +++ b/drivers/block/null_blk/main.c
>>>>> @@ -762,7 +762,7 @@ static struct nullb_device *null_alloc_dev(void)
>>>>> return NULL;
>>>>> }
>>>>> - dev->size = g_gb * 1024;
>>>>> + dev->size = (unsigned long)g_gb * 1024;
>>>>
>>>> This still does not prevent overflows... So what about doing a
>>>> proper check ?
>>>
>>> This still does not prevent overflows on 32-bits architectures.
>>
>> Because "unsigned long" on 32-bits architectures is 32 bit, so
>> solution 1 is to change the type "unsigned long" to u64, and the diff
>> is as below:
>>
>> diff --git a/drivers/block/null_blk/main.c
>> b/drivers/block/null_blk/main.c
>> index 2f0431e42c49..27a453b3094d 100644
>> --- a/drivers/block/null_blk/main.c
>> +++ b/drivers/block/null_blk/main.c
>> @@ -762,7 +762,7 @@ static struct nullb_device *null_alloc_dev(void)
>> return NULL;
>> }
>>
>> - dev->size = g_gb * 1024;
>> + dev->size = (u64)g_gb * 1024;
>> dev->completion_nsec = g_completion_nsec;
>> dev->submit_queues = g_submit_queues;
>> dev->prev_submit_queues = g_submit_queues;
>> diff --git a/drivers/block/null_blk/null_blk.h
>> b/drivers/block/null_blk/null_blk.h
>> index a7bb32f73ec3..e30c011909ad 100644
>> --- a/drivers/block/null_blk/null_blk.h
>> +++ b/drivers/block/null_blk/null_blk.h
>> @@ -74,7 +74,7 @@ struct nullb_device {
>> bool need_zone_res_mgmt;
>> spinlock_t zone_res_lock;
>>
>> - unsigned long size; /* device size in MB */
>> + u64 size; /* device size in MB */
>
> There is more, g_gb is GB, dev->size is MB, and dev->size will be used
> later for inode size in bytes, and bdev size in sectors.
>
> The max inode size is LONG_MAX, this is still more than UINT_MAX GB, so
> it's right that set the device size by module params won't overflow.
>
> However, take a look at setting the size through configfs, the max value
> is ULONG_MAX MB, this will still overflow.
Thanks a lot.
Add nullb_device_u64_attr_show and nullb_device_u64_attr_store functions.
So configfs should work well. Just a draft patch to try to fix this
overflow problem.
I just built it and did not make tests.
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 2f0431e42c49..56ee04277b92 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -289,6 +289,12 @@ static inline ssize_t
nullb_device_ulong_attr_show(unsigned long val,
return snprintf(page, PAGE_SIZE, "%lu\n", val);
}
+static inline ssize_t nullb_device_u64_attr_show(u64 val,
+ char *page)
+{
+ return snprintf(page, PAGE_SIZE, "%llu\n", val);
+}
+
static inline ssize_t nullb_device_bool_attr_show(bool val, char *page)
{
return snprintf(page, PAGE_SIZE, "%u\n", val);
@@ -322,6 +328,20 @@ static ssize_t
nullb_device_ulong_attr_store(unsigned long *val,
return count;
}
+static ssize_t nullb_device_u64_attr_store(u64 *val,
+ const char *page, size_t count)
+{
+ int result;
+ u64 tmp;
+
+ result = kstrtou64(page, 0, &tmp);
+ if (result < 0)
+ return result;
+
+ *val = tmp;
+ return count;
+}
+
static ssize_t nullb_device_bool_attr_store(bool *val, const char *page,
size_t count)
{
@@ -438,7 +458,7 @@ static int nullb_apply_poll_queues(struct
nullb_device *dev,
return ret;
}
-NULLB_DEVICE_ATTR(size, ulong, NULL);
+NULLB_DEVICE_ATTR(size, u64, NULL);
NULLB_DEVICE_ATTR(completion_nsec, ulong, NULL);
NULLB_DEVICE_ATTR(submit_queues, uint, nullb_apply_submit_queues);
NULLB_DEVICE_ATTR(poll_queues, uint, nullb_apply_poll_queues);
@@ -762,7 +782,7 @@ static struct nullb_device *null_alloc_dev(void)
return NULL;
}
- dev->size = g_gb * 1024;
+ dev->size = (u64)g_gb * 1024;
dev->completion_nsec = g_completion_nsec;
dev->submit_queues = g_submit_queues;
dev->prev_submit_queues = g_submit_queues;
diff --git a/drivers/block/null_blk/null_blk.h
b/drivers/block/null_blk/null_blk.h
index a7bb32f73ec3..e30c011909ad 100644
--- a/drivers/block/null_blk/null_blk.h
+++ b/drivers/block/null_blk/null_blk.h
@@ -74,7 +74,7 @@ struct nullb_device {
bool need_zone_res_mgmt;
spinlock_t zone_res_lock;
- unsigned long size; /* device size in MB */
+ u64 size; /* device size in MB */
unsigned long completion_nsec; /* time in ns to complete a
request */
unsigned long cache_size; /* disk cache size in MB */
unsigned long zone_size; /* zone size in MB if device is zoned */
Zhu Yanjun
>
> Thanks,
> Kuai
>
>> unsigned long completion_nsec; /* time in ns to complete a
>> request */
>> unsigned long cache_size; /* disk cache size in MB */
>> unsigned long zone_size; /* zone size in MB if device is
>> zoned */
>>
>> I just built it and did not make tests.
>>
>> Zhu Yanjun
>>
>>>
>>>>
>>>>> dev->completion_nsec = g_completion_nsec;
>>>>> dev->submit_queues = g_submit_queues;
>>>>> dev->prev_submit_queues = g_submit_queues;
>>>>
>>>
>>
>>
>> .
>>
>
--
Best Regards,
Yanjun.Zhu
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