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.haefli...@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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