Jeff Layton <jlayton@xxxxxxxxxx> writes: > 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. Hmm, yeah. I guess the changelog could mention that. Thanks, Jeff. Cheers, -- Luis >> > 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> >
