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 <[email protected]> >>>>> --- >>>>> 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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