[PATCH] jfs: Add missing NULL pointer check in __get_metapage

[PATCH] jfs: Add missing NULL pointer check in __get_metapage

[Juerg Haefliger]

alloc_metapage can return a NULL pointer so check for that. And also emit
an error message if that happens.

Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
---
 fs/jfs/jfs_metapage.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/fs/jfs/jfs_metapage.c b/fs/jfs/jfs_metapage.c
index 1c4b9ad4d7ab..00f21af66872 100644
--- a/fs/jfs/jfs_metapage.c
+++ b/fs/jfs/jfs_metapage.c
@@ -187,14 +187,18 @@ static inline struct metapage *alloc_metapage(gfp_t gfp_mask)
 {
 	struct metapage *mp = mempool_alloc(metapage_mempool, gfp_mask);
 
-	if (mp) {
-		mp->lid = 0;
-		mp->lsn = 0;
-		mp->data = NULL;
-		mp->clsn = 0;
-		mp->log = NULL;
-		init_waitqueue_head(&mp->wait);
+	if (!mp) {
+		jfs_err("mempool_alloc failed!\n");
+		return NULL;
 	}
+
+	mp->lid = 0;
+	mp->lsn = 0;
+	mp->data = NULL;
+	mp->clsn = 0;
+	mp->log = NULL;
+	init_waitqueue_head(&mp->wait);
+
 	return mp;
 }
 
@@ -663,6 +667,8 @@ struct metapage *__get_metapage(struct inode *inode, unsigned long lblock,
 	} else {
 		INCREMENT(mpStat.pagealloc);
 		mp = alloc_metapage(GFP_NOFS);
+		if (!mp)
+			goto unlock;
 		mp->page = page;
 		mp->sb = inode->i_sb;
 		mp->flag = 0;
-- 
2.14.1

Re: [PATCH] jfs: Add missing NULL pointer check in __get_metapage

[Juerg Haefliger]

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Is this a patch you might consider?

Thanks
...Juerg


On 10/04/2017 10:24 AM, Juerg Haefliger wrote:
> alloc_metapage can return a NULL pointer so check for that. And also emit
> an error message if that happens.
> 
> Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
> ---
>  fs/jfs/jfs_metapage.c | 20 +++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/jfs/jfs_metapage.c b/fs/jfs/jfs_metapage.c
> index 1c4b9ad4d7ab..00f21af66872 100644
> --- a/fs/jfs/jfs_metapage.c
> +++ b/fs/jfs/jfs_metapage.c
> @@ -187,14 +187,18 @@ static inline struct metapage *alloc_metapage(gfp_t gfp_mask)
>  {
>  	struct metapage *mp = mempool_alloc(metapage_mempool, gfp_mask);
>  
> -	if (mp) {
> -		mp->lid = 0;
> -		mp->lsn = 0;
> -		mp->data = NULL;
> -		mp->clsn = 0;
> -		mp->log = NULL;
> -		init_waitqueue_head(&mp->wait);
> +	if (!mp) {
> +		jfs_err("mempool_alloc failed!\n");
> +		return NULL;
>  	}
> +
> +	mp->lid = 0;
> +	mp->lsn = 0;
> +	mp->data = NULL;
> +	mp->clsn = 0;
> +	mp->log = NULL;
> +	init_waitqueue_head(&mp->wait);
> +
>  	return mp;
>  }
>  
> @@ -663,6 +667,8 @@ struct metapage *__get_metapage(struct inode *inode, unsigned long lblock,
>  	} else {
>  		INCREMENT(mpStat.pagealloc);
>  		mp = alloc_metapage(GFP_NOFS);
> +		if (!mp)
> +			goto unlock;
>  		mp->page = page;
>  		mp->sb = inode->i_sb;
>  		mp->flag = 0;
> 


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Re: [Jfs-discussion] [PATCH] jfs: Add missing NULL pointer check in __get_metapage

[Dave Kleikamp]

On 10/25/2017 02:50 AM, Juerg Haefliger wrote:
> Is this a patch you might consider?

Sorry it's taken me so long to respond.

I don't think this is the right fix. A failed allocation will still
result in a null pointer dereference by the caller, __get_metapage(). I
think the check needs to be put there. Like this:

--- a/fs/jfs/jfs_metapage.c
+++ b/fs/jfs/jfs_metapage.c
@@ -663,6 +663,8 @@ struct metapage *__get_metapage(struct inode *inode,
unsigned long lblock,
 	} else {
 		INCREMENT(mpStat.pagealloc);
 		mp = alloc_metapage(GFP_NOFS);
+		if (!mp)
+			goto unlock;
 		mp->page = page;
 		mp->sb = inode->i_sb;
 		mp->flag = 0;


Furthermore, it looks like all the callers of __get_metapage() check for
a null return, so I'm not sure we need to handle the error at this
point. I might have to look a bit harder at that, since there are many
callers.

Thanks,
Shaggy

> 
> Thanks
> ...Juerg
> 
> 
> On 10/04/2017 10:24 AM, Juerg Haefliger wrote:
>> alloc_metapage can return a NULL pointer so check for that. And also emit
>> an error message if that happens.
>>
>> Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
>> ---
>>  fs/jfs/jfs_metapage.c | 20 +++++++++++++-------
>>  1 file changed, 13 insertions(+), 7 deletions(-)
>>
>> diff --git a/fs/jfs/jfs_metapage.c b/fs/jfs/jfs_metapage.c
>> index 1c4b9ad4d7ab..00f21af66872 100644
>> --- a/fs/jfs/jfs_metapage.c
>> +++ b/fs/jfs/jfs_metapage.c
>> @@ -187,14 +187,18 @@ static inline struct metapage *alloc_metapage(gfp_t gfp_mask)
>>  {
>>  	struct metapage *mp = mempool_alloc(metapage_mempool, gfp_mask);
>>  
>> -	if (mp) {
>> -		mp->lid = 0;
>> -		mp->lsn = 0;
>> -		mp->data = NULL;
>> -		mp->clsn = 0;
>> -		mp->log = NULL;
>> -		init_waitqueue_head(&mp->wait);
>> +	if (!mp) {
>> +		jfs_err("mempool_alloc failed!\n");
>> +		return NULL;
>>  	}
>> +
>> +	mp->lid = 0;
>> +	mp->lsn = 0;
>> +	mp->data = NULL;
>> +	mp->clsn = 0;
>> +	mp->log = NULL;
>> +	init_waitqueue_head(&mp->wait);
>> +
>>  	return mp;
>>  }
>>  
>> @@ -663,6 +667,8 @@ struct metapage *__get_metapage(struct inode *inode, unsigned long lblock,
>>  	} else {
>>  		INCREMENT(mpStat.pagealloc);
>>  		mp = alloc_metapage(GFP_NOFS);
>> +		if (!mp)
>> +			goto unlock;
>>  		mp->page = page;
>>  		mp->sb = inode->i_sb;
>>  		mp->flag = 0;
>>

Re: [Jfs-discussion] [PATCH] jfs: Add missing NULL pointer check in __get_metapage

[Juerg Haefliger]

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On 10/30/2017 11:13 PM, Dave Kleikamp wrote:
> On 10/25/2017 02:50 AM, Juerg Haefliger wrote:
>> Is this a patch you might consider?
> 
> Sorry it's taken me so long to respond.
> 
> I don't think this is the right fix. A failed allocation will still
> result in a null pointer dereference by the caller, __get_metapage(). I
> think the check needs to be put there. Like this:
> 
> --- a/fs/jfs/jfs_metapage.c
> +++ b/fs/jfs/jfs_metapage.c
> @@ -663,6 +663,8 @@ struct metapage *__get_metapage(struct inode *inode,
> unsigned long lblock,
>  	} else {
>  		INCREMENT(mpStat.pagealloc);
>  		mp = alloc_metapage(GFP_NOFS);
> +		if (!mp)
> +			goto unlock;
>  		mp->page = page;
>  		mp->sb = inode->i_sb;
>  		mp->flag = 0;

I don't understand. This is part of the patch that I sent.


> 
> Furthermore, it looks like all the callers of __get_metapage() check for
> a null return, so I'm not sure we need to handle the error at this
> point. I might have to look a bit harder at that, since there are many
> callers.

I don't understand this either :-) Yes, the callers do check for a null
pointer but things blow up (in __get_metapage) before that check without
the above fix.

...Juerg


> 
> Thanks,
> Shaggy
> 
>>
>> Thanks
>> ...Juerg
>>
>>
>> On 10/04/2017 10:24 AM, Juerg Haefliger wrote:
>>> alloc_metapage can return a NULL pointer so check for that. And also emit
>>> an error message if that happens.
>>>
>>> Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
>>> ---
>>>  fs/jfs/jfs_metapage.c | 20 +++++++++++++-------
>>>  1 file changed, 13 insertions(+), 7 deletions(-)
>>>
>>> diff --git a/fs/jfs/jfs_metapage.c b/fs/jfs/jfs_metapage.c
>>> index 1c4b9ad4d7ab..00f21af66872 100644
>>> --- a/fs/jfs/jfs_metapage.c
>>> +++ b/fs/jfs/jfs_metapage.c
>>> @@ -187,14 +187,18 @@ static inline struct metapage *alloc_metapage(gfp_t gfp_mask)
>>>  {
>>>  	struct metapage *mp = mempool_alloc(metapage_mempool, gfp_mask);
>>>  
>>> -	if (mp) {
>>> -		mp->lid = 0;
>>> -		mp->lsn = 0;
>>> -		mp->data = NULL;
>>> -		mp->clsn = 0;
>>> -		mp->log = NULL;
>>> -		init_waitqueue_head(&mp->wait);
>>> +	if (!mp) {
>>> +		jfs_err("mempool_alloc failed!\n");
>>> +		return NULL;
>>>  	}
>>> +
>>> +	mp->lid = 0;
>>> +	mp->lsn = 0;
>>> +	mp->data = NULL;
>>> +	mp->clsn = 0;
>>> +	mp->log = NULL;
>>> +	init_waitqueue_head(&mp->wait);
>>> +
>>>  	return mp;
>>>  }
>>>  
>>> @@ -663,6 +667,8 @@ struct metapage *__get_metapage(struct inode *inode, unsigned long lblock,
>>>  	} else {
>>>  		INCREMENT(mpStat.pagealloc);
>>>  		mp = alloc_metapage(GFP_NOFS);
>>> +		if (!mp)
>>> +			goto unlock;
>>>  		mp->page = page;
>>>  		mp->sb = inode->i_sb;
>>>  		mp->flag = 0;
>>>


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Re: [Jfs-discussion] [PATCH] jfs: Add missing NULL pointer check in __get_metapage

[Dave Kleikamp]

On 11/02/2017 01:59 AM, Juerg Haefliger wrote:
> 
> 
> On 10/30/2017 11:13 PM, Dave Kleikamp wrote:
>> On 10/25/2017 02:50 AM, Juerg Haefliger wrote:
>>> Is this a patch you might consider?
>>
>> Sorry it's taken me so long to respond.
>>
>> I don't think this is the right fix. A failed allocation will still
>> result in a null pointer dereference by the caller, __get_metapage(). I
>> think the check needs to be put there. Like this:
>>
>> --- a/fs/jfs/jfs_metapage.c
>> +++ b/fs/jfs/jfs_metapage.c
>> @@ -663,6 +663,8 @@ struct metapage *__get_metapage(struct inode *inode,
>> unsigned long lblock,
>>  	} else {
>>  		INCREMENT(mpStat.pagealloc);
>>  		mp = alloc_metapage(GFP_NOFS);
>> +		if (!mp)
>> +			goto unlock;
>>  		mp->page = page;
>>  		mp->sb = inode->i_sb;
>>  		mp->flag = 0;
> 
> I don't understand. This is part of the patch that I sent.

Doh! How'd I miss that?

> 
> 
>>
>> Furthermore, it looks like all the callers of __get_metapage() check for
>> a null return, so I'm not sure we need to handle the error at this
>> point. I might have to look a bit harder at that, since there are many
>> callers.
> 
> I don't understand this either :-) Yes, the callers do check for a null
> pointer but things blow up (in __get_metapage) before that check without
> the above fix.

Yeah, the fix to __get_metapage() is necessary. I'm not convinced the
first part of the patch, to alloc_metapage(), is necessary.

> 
> ...Juerg
> 
> 
>>
>> Thanks,
>> Shaggy
>>
>>>
>>> Thanks
>>> ...Juerg
>>>
>>>
>>> On 10/04/2017 10:24 AM, Juerg Haefliger wrote:
>>>> alloc_metapage can return a NULL pointer so check for that. And also emit
>>>> an error message if that happens.
>>>>
>>>> Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
>>>> ---
>>>>  fs/jfs/jfs_metapage.c | 20 +++++++++++++-------
>>>>  1 file changed, 13 insertions(+), 7 deletions(-)
>>>>
>>>> diff --git a/fs/jfs/jfs_metapage.c b/fs/jfs/jfs_metapage.c
>>>> index 1c4b9ad4d7ab..00f21af66872 100644
>>>> --- a/fs/jfs/jfs_metapage.c
>>>> +++ b/fs/jfs/jfs_metapage.c
>>>> @@ -187,14 +187,18 @@ static inline struct metapage *alloc_metapage(gfp_t gfp_mask)
>>>>  {
>>>>  	struct metapage *mp = mempool_alloc(metapage_mempool, gfp_mask);
>>>>  
>>>> -	if (mp) {
>>>> -		mp->lid = 0;
>>>> -		mp->lsn = 0;
>>>> -		mp->data = NULL;
>>>> -		mp->clsn = 0;
>>>> -		mp->log = NULL;
>>>> -		init_waitqueue_head(&mp->wait);
>>>> +	if (!mp) {
>>>> +		jfs_err("mempool_alloc failed!\n");
>>>> +		return NULL;
>>>>  	}
>>>> +
>>>> +	mp->lid = 0;
>>>> +	mp->lsn = 0;
>>>> +	mp->data = NULL;
>>>> +	mp->clsn = 0;
>>>> +	mp->log = NULL;
>>>> +	init_waitqueue_head(&mp->wait);
>>>> +
>>>>  	return mp;
>>>>  }
>>>>  
>>>> @@ -663,6 +667,8 @@ struct metapage *__get_metapage(struct inode *inode, unsigned long lblock,
>>>>  	} else {
>>>>  		INCREMENT(mpStat.pagealloc);
>>>>  		mp = alloc_metapage(GFP_NOFS);
>>>> +		if (!mp)
>>>> +			goto unlock;
>>>>  		mp->page = page;
>>>>  		mp->sb = inode->i_sb;
>>>>  		mp->flag = 0;
>>>>
> 

Re: [Jfs-discussion] [PATCH] jfs: Add missing NULL pointer check in __get_metapage

[Juerg Haefliger]

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On 11/02/2017 02:15 PM, Dave Kleikamp wrote:
> On 11/02/2017 01:59 AM, Juerg Haefliger wrote:
>>
>>
>> On 10/30/2017 11:13 PM, Dave Kleikamp wrote:
>>> On 10/25/2017 02:50 AM, Juerg Haefliger wrote:
>>>> Is this a patch you might consider?
>>>
>>> Sorry it's taken me so long to respond.
>>>
>>> I don't think this is the right fix. A failed allocation will still
>>> result in a null pointer dereference by the caller, __get_metapage(). I
>>> think the check needs to be put there. Like this:
>>>
>>> --- a/fs/jfs/jfs_metapage.c
>>> +++ b/fs/jfs/jfs_metapage.c
>>> @@ -663,6 +663,8 @@ struct metapage *__get_metapage(struct inode *inode,
>>> unsigned long lblock,
>>>  	} else {
>>>  		INCREMENT(mpStat.pagealloc);
>>>  		mp = alloc_metapage(GFP_NOFS);
>>> +		if (!mp)
>>> +			goto unlock;
>>>  		mp->page = page;
>>>  		mp->sb = inode->i_sb;
>>>  		mp->flag = 0;
>>
>> I don't understand. This is part of the patch that I sent.
> 
> Doh! How'd I miss that?

:-)


>>
>>
>>>
>>> Furthermore, it looks like all the callers of __get_metapage() check for
>>> a null return, so I'm not sure we need to handle the error at this
>>> point. I might have to look a bit harder at that, since there are many
>>> callers.
>>
>> I don't understand this either :-) Yes, the callers do check for a null
>> pointer but things blow up (in __get_metapage) before that check without
>> the above fix.
> 
> Yeah, the fix to __get_metapage() is necessary. I'm not convinced the
> first part of the patch, to alloc_metapage(), is necessary.

It's not. I just thought it'd be nice to get some sort of notification
in the log when the alloc fails. But if the callers log it then that's fine.

...Juerg


>>
>> ...Juerg
>>
>>
>>>
>>> Thanks,
>>> Shaggy
>>>
>>>>
>>>> Thanks
>>>> ...Juerg
>>>>
>>>>
>>>> On 10/04/2017 10:24 AM, Juerg Haefliger wrote:
>>>>> alloc_metapage can return a NULL pointer so check for that. And also emit
>>>>> an error message if that happens.
>>>>>
>>>>> Signed-off-by: Juerg Haefliger <juerg.haefliger@canonical.com>
>>>>> ---
>>>>>  fs/jfs/jfs_metapage.c | 20 +++++++++++++-------
>>>>>  1 file changed, 13 insertions(+), 7 deletions(-)
>>>>>
>>>>> diff --git a/fs/jfs/jfs_metapage.c b/fs/jfs/jfs_metapage.c
>>>>> index 1c4b9ad4d7ab..00f21af66872 100644
>>>>> --- a/fs/jfs/jfs_metapage.c
>>>>> +++ b/fs/jfs/jfs_metapage.c
>>>>> @@ -187,14 +187,18 @@ static inline struct metapage *alloc_metapage(gfp_t gfp_mask)
>>>>>  {
>>>>>  	struct metapage *mp = mempool_alloc(metapage_mempool, gfp_mask);
>>>>>  
>>>>> -	if (mp) {
>>>>> -		mp->lid = 0;
>>>>> -		mp->lsn = 0;
>>>>> -		mp->data = NULL;
>>>>> -		mp->clsn = 0;
>>>>> -		mp->log = NULL;
>>>>> -		init_waitqueue_head(&mp->wait);
>>>>> +	if (!mp) {
>>>>> +		jfs_err("mempool_alloc failed!\n");
>>>>> +		return NULL;
>>>>>  	}
>>>>> +
>>>>> +	mp->lid = 0;
>>>>> +	mp->lsn = 0;
>>>>> +	mp->data = NULL;
>>>>> +	mp->clsn = 0;
>>>>> +	mp->log = NULL;
>>>>> +	init_waitqueue_head(&mp->wait);
>>>>> +
>>>>>  	return mp;
>>>>>  }
>>>>>  
>>>>> @@ -663,6 +667,8 @@ struct metapage *__get_metapage(struct inode *inode, unsigned long lblock,
>>>>>  	} else {
>>>>>  		INCREMENT(mpStat.pagealloc);
>>>>>  		mp = alloc_metapage(GFP_NOFS);
>>>>> +		if (!mp)
>>>>> +			goto unlock;
>>>>>  		mp->page = page;
>>>>>  		mp->sb = inode->i_sb;
>>>>>  		mp->flag = 0;
>>>>>
>>


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Re: [Jfs-discussion] [PATCH] jfs: Add missing NULL pointer check in __get_metapage

[Dave Kleikamp]

On 11/02/2017 08:43 AM, Juerg Haefliger wrote:

>>>> Furthermore, it looks like all the callers of __get_metapage() check for
>>>> a null return, so I'm not sure we need to handle the error at this
>>>> point. I might have to look a bit harder at that, since there are many
>>>> callers.
>>>
>>> I don't understand this either :-) Yes, the callers do check for a null
>>> pointer but things blow up (in __get_metapage) before that check without
>>> the above fix.
>>
>> Yeah, the fix to __get_metapage() is necessary. I'm not convinced the
>> first part of the patch, to alloc_metapage(), is necessary.
> 
> It's not. I just thought it'd be nice to get some sort of notification
> in the log when the alloc fails. But if the callers log it then that's fine.

Okay. I'll push just the __get_metapage part of your patch.

Thanks,
Shaggy