xiubli@xxxxxxxxxx writes: > From: Xiubo Li <xiubli@xxxxxxxxxx> > > When trimming the caps and just after the 'session->s_cap_lock' is > released in ceph_iterate_session_caps() the cap maybe removed by > another thread, and when using the stale cap memory in the callbacks > it will trigger use-after-free crash. > > We need to check the existence of the cap just after the 'ci->i_ceph_lock' > being acquired. And do nothing if it's already removed. Your patch seems to be OK, but I'll be honest: the locking is *so* complex that I can say for sure it really solves any problem :-( ceph_put_cap() uses mdsc->caps_list_lock to protect the list, but I can't be sure that holding ci->i_ceph_lock will protect a race in the case you're trying to solve. Is the issue in that bugzilla reproducible, or was that a one-time thing? Cheers, -- Luís > Cc: stable@xxxxxxxxxxxxxxx > URL: https://bugzilla.redhat.com/show_bug.cgi?id=2186264 > URL: https://tracker.ceph.com/issues/43272 > Signed-off-by: Xiubo Li <xiubli@xxxxxxxxxx> > --- > > V3: > - Fixed 3 issues, which reported by Luis and kernel test robot <lkp@xxxxxxxxx> > > fs/ceph/debugfs.c | 7 ++++- > fs/ceph/mds_client.c | 68 +++++++++++++++++++++++++++++--------------- > fs/ceph/mds_client.h | 2 +- > 3 files changed, 52 insertions(+), 25 deletions(-) > > diff --git a/fs/ceph/debugfs.c b/fs/ceph/debugfs.c > index bec3c4549c07..5c0f07df5b02 100644 > --- a/fs/ceph/debugfs.c > +++ b/fs/ceph/debugfs.c > @@ -248,14 +248,19 @@ static int metrics_caps_show(struct seq_file *s, void *p) > return 0; > } > > -static int caps_show_cb(struct inode *inode, struct ceph_cap *cap, void *p) > +static int caps_show_cb(struct inode *inode, struct rb_node *ci_node, void *p) > { > + struct ceph_inode_info *ci = ceph_inode(inode); > struct seq_file *s = p; > + struct ceph_cap *cap; > > + spin_lock(&ci->i_ceph_lock); > + cap = rb_entry(ci_node, struct ceph_cap, ci_node); > seq_printf(s, "0x%-17llx%-3d%-17s%-17s\n", ceph_ino(inode), > cap->session->s_mds, > ceph_cap_string(cap->issued), > ceph_cap_string(cap->implemented)); > + spin_unlock(&ci->i_ceph_lock); > return 0; > } > > diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c > index 294af79c25c9..fb777add2257 100644 > --- a/fs/ceph/mds_client.c > +++ b/fs/ceph/mds_client.c > @@ -1786,7 +1786,7 @@ static void cleanup_session_requests(struct ceph_mds_client *mdsc, > * Caller must hold session s_mutex. > */ > int ceph_iterate_session_caps(struct ceph_mds_session *session, > - int (*cb)(struct inode *, struct ceph_cap *, > + int (*cb)(struct inode *, struct rb_node *ci_node, > void *), void *arg) > { > struct list_head *p; > @@ -1799,6 +1799,8 @@ int ceph_iterate_session_caps(struct ceph_mds_session *session, > spin_lock(&session->s_cap_lock); > p = session->s_caps.next; > while (p != &session->s_caps) { > + struct rb_node *ci_node; > + > cap = list_entry(p, struct ceph_cap, session_caps); > inode = igrab(&cap->ci->netfs.inode); > if (!inode) { > @@ -1806,6 +1808,7 @@ int ceph_iterate_session_caps(struct ceph_mds_session *session, > continue; > } > session->s_cap_iterator = cap; > + ci_node = &cap->ci_node; > spin_unlock(&session->s_cap_lock); > > if (last_inode) { > @@ -1817,7 +1820,7 @@ int ceph_iterate_session_caps(struct ceph_mds_session *session, > old_cap = NULL; > } > > - ret = cb(inode, cap, arg); > + ret = cb(inode, ci_node, arg); > last_inode = inode; > > spin_lock(&session->s_cap_lock); > @@ -1850,20 +1853,26 @@ int ceph_iterate_session_caps(struct ceph_mds_session *session, > return ret; > } > > -static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap, > +static int remove_session_caps_cb(struct inode *inode, struct rb_node *ci_node, > void *arg) > { > struct ceph_inode_info *ci = ceph_inode(inode); > bool invalidate = false; > - int iputs; > + struct ceph_cap *cap; > + int iputs = 0; > > - dout("removing cap %p, ci is %p, inode is %p\n", > - cap, ci, &ci->netfs.inode); > spin_lock(&ci->i_ceph_lock); > - iputs = ceph_purge_inode_cap(inode, cap, &invalidate); > + cap = rb_entry(ci_node, struct ceph_cap, ci_node); > + if (cap) { > + dout(" removing cap %p, ci is %p, inode is %p\n", > + cap, ci, &ci->netfs.inode); > + > + iputs = ceph_purge_inode_cap(inode, cap, &invalidate); > + } > spin_unlock(&ci->i_ceph_lock); > > - wake_up_all(&ci->i_cap_wq); > + if (cap) > + wake_up_all(&ci->i_cap_wq); > if (invalidate) > ceph_queue_invalidate(inode); > while (iputs--) > @@ -1934,8 +1943,7 @@ enum { > * > * caller must hold s_mutex. > */ > -static int wake_up_session_cb(struct inode *inode, struct ceph_cap *cap, > - void *arg) > +static int wake_up_session_cb(struct inode *inode, struct rb_node *ci_node, void *arg) > { > struct ceph_inode_info *ci = ceph_inode(inode); > unsigned long ev = (unsigned long)arg; > @@ -1946,12 +1954,14 @@ static int wake_up_session_cb(struct inode *inode, struct ceph_cap *cap, > ci->i_requested_max_size = 0; > spin_unlock(&ci->i_ceph_lock); > } else if (ev == RENEWCAPS) { > - if (cap->cap_gen < atomic_read(&cap->session->s_cap_gen)) { > - /* mds did not re-issue stale cap */ > - spin_lock(&ci->i_ceph_lock); > + struct ceph_cap *cap; > + > + spin_lock(&ci->i_ceph_lock); > + cap = rb_entry(ci_node, struct ceph_cap, ci_node); > + /* mds did not re-issue stale cap */ > + if (cap && cap->cap_gen < atomic_read(&cap->session->s_cap_gen)) > cap->issued = cap->implemented = CEPH_CAP_PIN; > - spin_unlock(&ci->i_ceph_lock); > - } > + spin_unlock(&ci->i_ceph_lock); > } else if (ev == FORCE_RO) { > } > wake_up_all(&ci->i_cap_wq); > @@ -2113,16 +2123,22 @@ static bool drop_negative_children(struct dentry *dentry) > * Yes, this is a bit sloppy. Our only real goal here is to respond to > * memory pressure from the MDS, though, so it needn't be perfect. > */ > -static int trim_caps_cb(struct inode *inode, struct ceph_cap *cap, void *arg) > +static int trim_caps_cb(struct inode *inode, struct rb_node *ci_node, void *arg) > { > int *remaining = arg; > struct ceph_inode_info *ci = ceph_inode(inode); > int used, wanted, oissued, mine; > + struct ceph_cap *cap; > > if (*remaining <= 0) > return -1; > > spin_lock(&ci->i_ceph_lock); > + cap = rb_entry(ci_node, struct ceph_cap, ci_node); > + if (!cap) { > + spin_unlock(&ci->i_ceph_lock); > + return 0; > + } > mine = cap->issued | cap->implemented; > used = __ceph_caps_used(ci); > wanted = __ceph_caps_file_wanted(ci); > @@ -4265,26 +4281,23 @@ static struct dentry* d_find_primary(struct inode *inode) > /* > * Encode information about a cap for a reconnect with the MDS. > */ > -static int reconnect_caps_cb(struct inode *inode, struct ceph_cap *cap, > +static int reconnect_caps_cb(struct inode *inode, struct rb_node *ci_node, > void *arg) > { > union { > struct ceph_mds_cap_reconnect v2; > struct ceph_mds_cap_reconnect_v1 v1; > } rec; > - struct ceph_inode_info *ci = cap->ci; > + struct ceph_inode_info *ci = ceph_inode(inode); > struct ceph_reconnect_state *recon_state = arg; > struct ceph_pagelist *pagelist = recon_state->pagelist; > struct dentry *dentry; > + struct ceph_cap *cap; > char *path; > - int pathlen = 0, err; > + int pathlen = 0, err = 0; > u64 pathbase; > u64 snap_follows; > > - dout(" adding %p ino %llx.%llx cap %p %lld %s\n", > - inode, ceph_vinop(inode), cap, cap->cap_id, > - ceph_cap_string(cap->issued)); > - > dentry = d_find_primary(inode); > if (dentry) { > /* set pathbase to parent dir when msg_version >= 2 */ > @@ -4301,6 +4314,15 @@ static int reconnect_caps_cb(struct inode *inode, struct ceph_cap *cap, > } > > spin_lock(&ci->i_ceph_lock); > + cap = rb_entry(ci_node, struct ceph_cap, ci_node); > + if (!cap) { > + spin_unlock(&ci->i_ceph_lock); > + goto out_err; > + } > + dout(" adding %p ino %llx.%llx cap %p %lld %s\n", > + inode, ceph_vinop(inode), cap, cap->cap_id, > + ceph_cap_string(cap->issued)); > + > cap->seq = 0; /* reset cap seq */ > cap->issue_seq = 0; /* and issue_seq */ > cap->mseq = 0; /* and migrate_seq */ > diff --git a/fs/ceph/mds_client.h b/fs/ceph/mds_client.h > index 0f70ca3cdb21..001b69d04307 100644 > --- a/fs/ceph/mds_client.h > +++ b/fs/ceph/mds_client.h > @@ -569,7 +569,7 @@ extern void ceph_queue_cap_reclaim_work(struct ceph_mds_client *mdsc); > extern void ceph_reclaim_caps_nr(struct ceph_mds_client *mdsc, int nr); > extern int ceph_iterate_session_caps(struct ceph_mds_session *session, > int (*cb)(struct inode *, > - struct ceph_cap *, void *), > + struct rb_node *ci_node, void *), > void *arg); > extern void ceph_mdsc_pre_umount(struct ceph_mds_client *mdsc); > > -- > > 2.39.2 >
