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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
f0054bb1e1 ("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: Tejun Heo <tj@kernel.org>
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Tejun Heo 2015-06-08 14:57:31 +09:00 committed by Jens Axboe
parent 5857cd637b
commit 412a19b64a
2 changed files with 24 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

50
fs/9p/v9fs.c
View File

@ -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);
}
/**

8
fs/9p/vfs_super.c
View File

@ -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);