Messages in this thread Patch in this message | | | Date | Thu, 11 Sep 2014 19:52:09 +0200 | From | Heinrich Schuchardt <> | Subject | Re: [PATCH] fsnotify: don't put user context if it was never assigned |
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Hello Sasha,
I have CCed Jan, because he has been the only one working on this file in the last 18 months.
A failure path in which group->inotify_data.user is not yet assigned starts here:
static struct fsnotify_group *inotify_new_group(unsigned int max_events) { ... oevent = kmalloc(sizeof(struct inotify_event_info), GFP_KERNEL); if (unlikely(!oevent)) { fsnotify_destroy_group(group); return ERR_PTR(-ENOMEM); }
So your check if (group->inotify_data.user) is reasonable.
3.17.0-rc3 compiles with the patch applied.
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
@Andrew Please, add the patch to the mm-tree.
Best regards
Heinrich Schuchardt
On 29.07.2014 15:25, Sasha Levin wrote: > On some failure paths we may attempt to free user context even > if it wasn't assigned yet. This will cause a NULL ptr deref > and a kernel BUG. > > Signed-off-by: Sasha Levin <sasha.levin@oracle.com> > --- > fs/notify/inotify/inotify_fsnotify.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c > index 43ab1e1..9c8187e 100644 > --- a/fs/notify/inotify/inotify_fsnotify.c > +++ b/fs/notify/inotify/inotify_fsnotify.c > @@ -165,8 +165,10 @@ static void inotify_free_group_priv(struct fsnotify_group *group) > /* ideally the idr is empty and we won't hit the BUG in the callback */ > idr_for_each(&group->inotify_data.idr, idr_callback, group); > idr_destroy(&group->inotify_data.idr); > - atomic_dec(&group->inotify_data.user->inotify_devs); > - free_uid(group->inotify_data.user); > + if (group->inotify_data.user) { > + atomic_dec(&group->inotify_data.user->inotify_devs); > + free_uid(group->inotify_data.user); > + } > } > > static void inotify_free_event(struct fsnotify_event *fsn_event) >
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