On Thu, 2020-11-12 at 20:43 +0800, Yan, Zheng wrote: > On Thu, Nov 12, 2020 at 6:48 PM Luis Henriques <lhenriques@xxxxxxx> wrote: > > > > A NULL pointer dereference may occur in __ceph_remove_cap with some of the > > callbacks used in ceph_iterate_session_caps, namely trim_caps_cb and > > remove_session_caps_cb. These aren't protected against the concurrent > > execution of __ceph_remove_cap. > > > > they are protected by session mutex, never get executed concurrently > Maybe not concurrently with one another, but the s_mutex is _not_ held when __ceph_remove_caps is called from ceph_evict_inode. We can't rely on it to protect this. > > Since the callers of this function hold the i_ceph_lock, the fix is simply > > a matter of returning immediately if caps->ci is NULL. > > > > Based on a patch from Jeff Layton. > > > > Cc: stable@xxxxxxxxxxxxxxx > > URL: https://tracker.ceph.com/issues/43272 > > Link: https://www.spinics.net/lists/ceph-devel/msg47064.html > > Signed-off-by: Luis Henriques <lhenriques@xxxxxxx> > > --- > > fs/ceph/caps.c | 11 +++++++++-- > > 1 file changed, 9 insertions(+), 2 deletions(-) > > > > diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c > > index ded4229c314a..443f164760d5 100644 > > --- a/fs/ceph/caps.c > > +++ b/fs/ceph/caps.c > > @@ -1140,12 +1140,19 @@ void __ceph_remove_cap(struct ceph_cap *cap, bool queue_release) > > { > > struct ceph_mds_session *session = cap->session; > > struct ceph_inode_info *ci = cap->ci; > > - struct ceph_mds_client *mdsc = > > - ceph_sb_to_client(ci->vfs_inode.i_sb)->mdsc; > > + struct ceph_mds_client *mdsc; > > int removed = 0; > > > > + /* 'ci' being NULL means he remove have already occurred */ > > + if (!ci) { > > + dout("%s: cap inode is NULL\n", __func__); > > + return; > > + } > > + > > dout("__ceph_remove_cap %p from %p\n", cap, &ci->vfs_inode); > > > > + mdsc = ceph_inode_to_client(&ci->vfs_inode)->mdsc; > > + > > /* remove from inode's cap rbtree, and clear auth cap */ > > rb_erase(&cap->ci_node, &ci->i_caps); > > if (ci->i_auth_cap == cap) { -- Jeff Layton <jlayton@xxxxxxxxxx>
