From: Xiubo Li xiubli@redhat.com

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.

Cc: stable@vger.kernel.org URL: https://bugzilla.redhat.com/show_bug.cgi?id=2186264 Signed-off-by: Xiubo Li xiubli@redhat.com ---

V2: - Fix this in ceph_iterate_session_caps instead.

fs/ceph/debugfs.c | 7 +++++- fs/ceph/mds_client.c | 56 ++++++++++++++++++++++++++++++-------------- fs/ceph/mds_client.h | 2 +- 3 files changed, 46 insertions(+), 19 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..7fcfbddd534d 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); @@ -1850,17 +1853,22 @@ 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; + struct ceph_cap *cap; int iputs;

- 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); @@ -1934,11 +1942,11 @@ 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; + struct ceph_cap *cap;

if (ev == RECONNECT) { spin_lock(&ci->i_ceph_lock); @@ -1949,7 +1957,9 @@ static int wake_up_session_cb(struct inode *inode, struct ceph_cap *cap, if (cap->cap_gen < atomic_read(&cap->session->s_cap_gen)) { /* mds did not re-issue stale cap */ spin_lock(&ci->i_ceph_lock); - cap->issued = cap->implemented = CEPH_CAP_PIN; + cap = rb_entry(ci_node, struct ceph_cap, ci_node); + if (cap) + cap->issued = cap->implemented = CEPH_CAP_PIN; spin_unlock(&ci->i_ceph_lock); } } else if (ev == FORCE_RO) { @@ -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_lock(&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);