Commit aaf67de7 authored by Xiubo Li's avatar Xiubo Li Committed by Ilya Dryomov
Browse files

ceph: fix potential use-after-free bug when trimming caps 

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
Link: https://tracker.ceph.com/issues/43272


Signed-off-by: default avatarXiubo Li <xiubli@redhat.com>
Reviewed-by: default avatarLuís Henriques <lhenriques@suse.de>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent 7d41870d

fs/ceph/caps.c

+1 −1
Original line number Diff line number Diff line
@@ -431,7 +431,7 @@ void ceph_reservation_status(struct ceph_fs_client *fsc, 
 *

 * Called with i_ceph_lock held.

 */

static struct ceph_cap *__get_cap_for_mds(struct ceph_inode_info *ci, int mds)

struct ceph_cap *__get_cap_for_mds(struct ceph_inode_info *ci, int mds)

{

	struct ceph_cap *cap;

	struct rb_node *n = ci->i_caps.rb_node;

fs/ceph/debugfs.c

+12 −6
Original line number Diff line number Diff line
@@ -248,14 +248,20 @@ 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, int mds, 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 = __get_cap_for_mds(ci, mds);

	if (cap)

		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;

}

fs/ceph/mds_client.c

+46 −26
Original line number Diff line number Diff line
@@ -1632,8 +1632,8 @@ 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 *,

					void *), void *arg)

			      int (*cb)(struct inode *, int mds, void *),

			      void *arg)

{

	struct list_head *p;

	struct ceph_cap *cap;
@@ -1645,6 +1645,8 @@ 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) {

		int mds;



		cap = list_entry(p, struct ceph_cap, session_caps);

		inode = igrab(&cap->ci->netfs.inode);

		if (!inode) {
@@ -1652,6 +1654,7 @@ int ceph_iterate_session_caps(struct ceph_mds_session *session, 
			continue;

		}

		session->s_cap_iterator = cap;

		mds = cap->mds;

		spin_unlock(&session->s_cap_lock);



		if (last_inode) {
@@ -1663,7 +1666,7 @@ int ceph_iterate_session_caps(struct ceph_mds_session *session, 
			old_cap = NULL;

		}



		ret = cb(inode, cap, arg);

		ret = cb(inode, mds, arg);

		last_inode = inode;



		spin_lock(&session->s_cap_lock);
@@ -1696,19 +1699,24 @@ 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,

				  void *arg)

static int remove_session_caps_cb(struct inode *inode, int mds, void *arg)

{

	struct ceph_inode_info *ci = ceph_inode(inode);

	bool invalidate = false;

	int iputs;

	struct ceph_cap *cap;

	int iputs = 0;



	spin_lock(&ci->i_ceph_lock);

	cap = __get_cap_for_mds(ci, mds);

	if (cap) {

		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);

	}

	spin_unlock(&ci->i_ceph_lock);



	if (cap)

		wake_up_all(&ci->i_cap_wq);

	if (invalidate)

		ceph_queue_invalidate(inode);
@@ -1780,8 +1788,7 @@ 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, int mds, void *arg)

{

	struct ceph_inode_info *ci = ceph_inode(inode);

	unsigned long ev = (unsigned long)arg;
@@ -1792,12 +1799,14 @@ 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 */

		struct ceph_cap *cap;



		spin_lock(&ci->i_ceph_lock);

		cap = __get_cap_for_mds(ci, mds);

		/* 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);

		}

	} else if (ev == FORCE_RO) {

	}

	wake_up_all(&ci->i_cap_wq);
@@ -1959,16 +1968,22 @@ 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, int mds, 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 = __get_cap_for_mds(ci, mds);

	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);
@@ -3911,26 +3926,22 @@ 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,

			  void *arg)

static int reconnect_caps_cb(struct inode *inode, int mds, 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 */
@@ -3947,6 +3958,15 @@ static int reconnect_caps_cb(struct inode *inode, struct ceph_cap *cap, 
	}



	spin_lock(&ci->i_ceph_lock);

	cap = __get_cap_for_mds(ci, mds);

	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 */

fs/ceph/mds_client.h

+1 −2
Original line number Diff line number Diff line
@@ -541,8 +541,7 @@ extern void ceph_flush_cap_releases(struct ceph_mds_client *mdsc, 
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 *),

				     int (*cb)(struct inode *, int mds, void *),

				     void *arg);

extern void ceph_mdsc_pre_umount(struct ceph_mds_client *mdsc);

fs/ceph/super.h

+2 −0
Original line number Diff line number Diff line
@@ -1192,6 +1192,8 @@ extern void ceph_kick_flushing_caps(struct ceph_mds_client *mdsc, 
				    struct ceph_mds_session *session);

void ceph_kick_flushing_inode_caps(struct ceph_mds_session *session,

				   struct ceph_inode_info *ci);

extern struct ceph_cap *__get_cap_for_mds(struct ceph_inode_info *ci,

					  int mds);

extern struct ceph_cap *ceph_get_cap_for_mds(struct ceph_inode_info *ci,

					     int mds);

extern void ceph_take_cap_refs(struct ceph_inode_info *ci, int caps,