Commit bec324f3 authored by Alex Markuze's avatar Alex Markuze Committed by Ilya Dryomov
Browse files

ceph: fix race condition where r_parent becomes stale before sending message 



When the parent directory's i_rwsem is not locked, req->r_parent may become
stale due to concurrent operations (e.g. rename) between dentry lookup and
message creation. Validate that r_parent matches the encoded parent inode
and update to the correct inode if a mismatch is detected.

[ idryomov: folded a follow-up fix from Alex to drop extra reference
  from ceph_get_reply_dir() in ceph_fill_trace():

  ceph_get_reply_dir() may return a different, referenced inode when
  r_parent is stale and the parent directory lock is not held.
  ceph_fill_trace() used that inode but failed to drop the reference
  when it differed from req->r_parent, leaking an inode reference.

  Keep the directory inode in a local variable and iput() it at
  function end if it does not match req->r_parent. ]

Cc: stable@vger.kernel.org
Signed-off-by: default avatarAlex Markuze <amarkuze@redhat.com>
Reviewed-by: default avatarViacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent 15f519e9

fs/ceph/inode.c

+69 −12
Original line number Diff line number Diff line
@@ -55,6 +55,52 @@ static int ceph_set_ino_cb(struct inode *inode, void *data) 
	return 0;

}



/*

 * Check if the parent inode matches the vino from directory reply info

 */

static inline bool ceph_vino_matches_parent(struct inode *parent,

					    struct ceph_vino vino)

{

	return ceph_ino(parent) == vino.ino && ceph_snap(parent) == vino.snap;

}



/*

 * Validate that the directory inode referenced by @req->r_parent matches the

 * inode number and snapshot id contained in the reply's directory record.  If

 * they do not match – which can theoretically happen if the parent dentry was

 * moved between the time the request was issued and the reply arrived – fall

 * back to looking up the correct inode in the inode cache.

 *

 * A reference is *always* returned.  Callers that receive a different inode

 * than the original @parent are responsible for dropping the extra reference

 * once the reply has been processed.

 */

static struct inode *ceph_get_reply_dir(struct super_block *sb,

					struct inode *parent,

					struct ceph_mds_reply_info_parsed *rinfo)

{

	struct ceph_vino vino;



	if (unlikely(!rinfo->diri.in))

		return parent; /* nothing to compare against */



	/* If we didn't have a cached parent inode to begin with, just bail out. */

	if (!parent)

		return NULL;



	vino.ino  = le64_to_cpu(rinfo->diri.in->ino);

	vino.snap = le64_to_cpu(rinfo->diri.in->snapid);



	if (likely(ceph_vino_matches_parent(parent, vino)))

		return parent; /* matches – use the original reference */



	/* Mismatch – this should be rare.  Emit a WARN and obtain the correct inode. */

	WARN_ONCE(1, "ceph: reply dir mismatch (parent valid %llx.%llx reply %llx.%llx)\n",

		  ceph_ino(parent), ceph_snap(parent), vino.ino, vino.snap);



	return ceph_get_inode(sb, vino, NULL);

}



/**

 * ceph_new_inode - allocate a new inode in advance of an expected create

 * @dir: parent directory for new inode
@@ -1523,6 +1569,7 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req) 
	struct ceph_vino tvino, dvino;

	struct ceph_fs_client *fsc = ceph_sb_to_fs_client(sb);

	struct ceph_client *cl = fsc->client;

	struct inode *parent_dir = NULL;

	int err = 0;



	doutc(cl, "%p is_dentry %d is_target %d\n", req,
@@ -1536,10 +1583,17 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req) 
	}



	if (rinfo->head->is_dentry) {

		struct inode *dir = req->r_parent;



		if (dir) {

			err = ceph_fill_inode(dir, NULL, &rinfo->diri,

		/*

		 * r_parent may be stale, in cases when R_PARENT_LOCKED is not set,

		 * so we need to get the correct inode

		 */

		parent_dir = ceph_get_reply_dir(sb, req->r_parent, rinfo);

		if (unlikely(IS_ERR(parent_dir))) {

			err = PTR_ERR(parent_dir);

			goto done;

		}

		if (parent_dir) {

			err = ceph_fill_inode(parent_dir, NULL, &rinfo->diri,

					      rinfo->dirfrag, session, -1,

					      &req->r_caps_reservation);

			if (err < 0)
@@ -1548,14 +1602,14 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req) 
			WARN_ON_ONCE(1);

		}



		if (dir && req->r_op == CEPH_MDS_OP_LOOKUPNAME &&

		if (parent_dir && req->r_op == CEPH_MDS_OP_LOOKUPNAME &&

		    test_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags) &&

		    !test_bit(CEPH_MDS_R_ABORTED, &req->r_req_flags)) {

			bool is_nokey = false;

			struct qstr dname;

			struct dentry *dn, *parent;

			struct fscrypt_str oname = FSTR_INIT(NULL, 0);

			struct ceph_fname fname = { .dir	= dir,

			struct ceph_fname fname = { .dir	= parent_dir,

						    .name	= rinfo->dname,

						    .ctext	= rinfo->altname,

						    .name_len	= rinfo->dname_len,
@@ -1564,10 +1618,10 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req) 
			BUG_ON(!rinfo->head->is_target);

			BUG_ON(req->r_dentry);



			parent = d_find_any_alias(dir);

			parent = d_find_any_alias(parent_dir);

			BUG_ON(!parent);



			err = ceph_fname_alloc_buffer(dir, &oname);

			err = ceph_fname_alloc_buffer(parent_dir, &oname);

			if (err < 0) {

				dput(parent);

				goto done;
@@ -1576,7 +1630,7 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req) 
			err = ceph_fname_to_usr(&fname, NULL, &oname, &is_nokey);

			if (err < 0) {

				dput(parent);

				ceph_fname_free_buffer(dir, &oname);

				ceph_fname_free_buffer(parent_dir, &oname);

				goto done;

			}

			dname.name = oname.name;
@@ -1595,7 +1649,7 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req) 
				      dname.len, dname.name, dn);

				if (!dn) {

					dput(parent);

					ceph_fname_free_buffer(dir, &oname);

					ceph_fname_free_buffer(parent_dir, &oname);

					err = -ENOMEM;

					goto done;

				}
@@ -1610,12 +1664,12 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req) 
				    ceph_snap(d_inode(dn)) != tvino.snap)) {

				doutc(cl, " dn %p points to wrong inode %p\n",

				      dn, d_inode(dn));

				ceph_dir_clear_ordered(dir);

				ceph_dir_clear_ordered(parent_dir);

				d_delete(dn);

				dput(dn);

				goto retry_lookup;

			}

			ceph_fname_free_buffer(dir, &oname);

			ceph_fname_free_buffer(parent_dir, &oname);



			req->r_dentry = dn;

			dput(parent);
@@ -1794,6 +1848,9 @@ int ceph_fill_trace(struct super_block *sb, struct ceph_mds_request *req) 
					    &dvino, ptvino);

	}

done:

	/* Drop extra ref from ceph_get_reply_dir() if it returned a new inode */

	if (unlikely(!IS_ERR_OR_NULL(parent_dir) && parent_dir != req->r_parent))

		iput(parent_dir);

	doutc(cl, "done err=%d\n", err);

	return err;

}