Messages in this thread | | | Subject | Re: [Jfs-discussion] [PATCH] jfs: Add missing NULL pointer check in __get_metapage | From | Juerg Haefliger <> | Date | Thu, 2 Nov 2017 07:59:09 +0100 |
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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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