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Commit 412a19b6 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
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v9fs: fix error handling in v9fs_session_init() 



On failure, v9fs_session_init() returns with the v9fs_session_info
struct partially initialized and expects the caller to invoke
v9fs_session_close() to clean it up; however, it doesn't track whether
the bdi is initialized or not and curiously invokes bdi_destroy() in
both vfs_session_init() failure path too.

A. If v9fs_session_init() fails before the bdi is initialized, the
   follow-up v9fs_session_close() will invoke bdi_destroy() on an
   uninitialized bdi.

B. If v9fs_session_init() fails after the bdi is initialized,
   bdi_destroy() will be called twice on the same bdi - once in the
   failure path of v9fs_session_init() and then by
   v9fs_session_close().

A is broken no matter what.  B used to be okay because bdi_destroy()
allowed being invoked multiple times on the same bdi, which BTW was
broken in its own way - if bdi_destroy() was invoked on an initialiezd
but !registered bdi, it'd fail to free percpu counters.  Since
f0054bb1 ("writeback: move backing_dev_info->wb_lock and
->worklist into bdi_writeback"), this no longer work - bdi_destroy()
on an initialized but not registered bdi works correctly but multiple
invocations of bdi_destroy() is no longer allowed.

The obvious culprit here is v9fs_session_init()'s odd and broken error
behavior.  It should simply clean up after itself on failures.  This
patch makes the following updates to v9fs_session_init().

* @rc -> @retval error return propagation removed.  It didn't serve
  any purpose.  Just use @rc.

* Move addition to v9fs_sessionlist to the end of the function so that
  incomplete sessions are not put on the list or iterated and error
  path doesn't have to worry about it.

* Update error handling so that it cleans up after itself.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reported-by: default avatarSasha Levin <sasha.levin@oracle.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 5857cd63

fs/9p/v9fs.c

+22 −28
Original line number Diff line number Diff line
@@ -320,31 +320,21 @@ static int v9fs_parse_options(struct v9fs_session_info *v9ses, char *opts) 
struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses,

		  const char *dev_name, char *data)

{

	int retval = -EINVAL;

	struct p9_fid *fid;

	int rc;

	int rc = -ENOMEM;



	v9ses->uname = kstrdup(V9FS_DEFUSER, GFP_KERNEL);

	if (!v9ses->uname)

		return ERR_PTR(-ENOMEM);

		goto err_names;



	v9ses->aname = kstrdup(V9FS_DEFANAME, GFP_KERNEL);

	if (!v9ses->aname) {

		kfree(v9ses->uname);

		return ERR_PTR(-ENOMEM);

	}

	if (!v9ses->aname)

		goto err_names;

	init_rwsem(&v9ses->rename_sem);



	rc = bdi_setup_and_register(&v9ses->bdi, "9p");

	if (rc) {

		kfree(v9ses->aname);

		kfree(v9ses->uname);

		return ERR_PTR(rc);

	}



	spin_lock(&v9fs_sessionlist_lock);

	list_add(&v9ses->slist, &v9fs_sessionlist);

	spin_unlock(&v9fs_sessionlist_lock);

	if (rc)

		goto err_names;



	v9ses->uid = INVALID_UID;

	v9ses->dfltuid = V9FS_DEFUID;
@@ -352,10 +342,9 @@ struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses, 


	v9ses->clnt = p9_client_create(dev_name, data);

	if (IS_ERR(v9ses->clnt)) {

		retval = PTR_ERR(v9ses->clnt);

		v9ses->clnt = NULL;

		rc = PTR_ERR(v9ses->clnt);

		p9_debug(P9_DEBUG_ERROR, "problem initializing 9p client\n");

		goto error;

		goto err_bdi;

	}



	v9ses->flags = V9FS_ACCESS_USER;
@@ -368,10 +357,8 @@ struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses, 
	}



	rc = v9fs_parse_options(v9ses, data);

	if (rc < 0) {

		retval = rc;

		goto error;

	}

	if (rc < 0)

		goto err_clnt;



	v9ses->maxdata = v9ses->clnt->msize - P9_IOHDRSZ;
@@ -405,10 +392,9 @@ struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses, 
	fid = p9_client_attach(v9ses->clnt, NULL, v9ses->uname, INVALID_UID,

							v9ses->aname);

	if (IS_ERR(fid)) {

		retval = PTR_ERR(fid);

		fid = NULL;

		rc = PTR_ERR(fid);

		p9_debug(P9_DEBUG_ERROR, "cannot attach\n");

		goto error;

		goto err_clnt;

	}



	if ((v9ses->flags & V9FS_ACCESS_MASK) == V9FS_ACCESS_SINGLE)
@@ -420,12 +406,20 @@ struct p9_fid *v9fs_session_init(struct v9fs_session_info *v9ses, 
	/* register the session for caching */

	v9fs_cache_session_get_cookie(v9ses);

#endif

	spin_lock(&v9fs_sessionlist_lock);

	list_add(&v9ses->slist, &v9fs_sessionlist);

	spin_unlock(&v9fs_sessionlist_lock);



	return fid;



error:

err_clnt:

	p9_client_destroy(v9ses->clnt);

err_bdi:

	bdi_destroy(&v9ses->bdi);

	return ERR_PTR(retval);

err_names:

	kfree(v9ses->uname);

	kfree(v9ses->aname);

	return ERR_PTR(rc);

}



/**

fs/9p/vfs_super.c

+2 −6
Original line number Diff line number Diff line
@@ -130,11 +130,7 @@ static struct dentry *v9fs_mount(struct file_system_type *fs_type, int flags, 
	fid = v9fs_session_init(v9ses, dev_name, data);

	if (IS_ERR(fid)) {

		retval = PTR_ERR(fid);

		/*

		 * we need to call session_close to tear down some

		 * of the data structure setup by session_init

		 */

		goto close_session;

		goto free_session;

	}



	sb = sget(fs_type, NULL, v9fs_set_super, flags, v9ses);
@@ -195,8 +191,8 @@ static struct dentry *v9fs_mount(struct file_system_type *fs_type, int flags, 


clunk_fid:

	p9_client_clunk(fid);

close_session:

	v9fs_session_close(v9ses);

free_session:

	kfree(v9ses);

	return ERR_PTR(retval);