diff options
| author | Tejun Heo <tj@kernel.org> | 2014-04-02 16:40:52 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-04-26 17:19:04 -0700 |
| commit | 29b311867df2f1f7aee9ec42517becbbb4aeeeef (patch) | |
| tree | 17533985d5559d114b9e3fb31163887c64caa6ff | |
| parent | 52d6c48c9db5b020e6595067a7f1b00562d26434 (diff) | |
kernfs: protect lazy kernfs_iattrs allocation with mutex
commit 4afddd60a770560d370d6f85c5aef57c16bf7502 upstream.
kernfs_iattrs is allocated lazily when operations which require it
take place; unfortunately, the lazy allocation and returning weren't
properly synchronized and when there are multiple concurrent
operations, it might end up returning kernfs_iattrs which hasn't
finished initialization yet or different copies to different callers.
Fix it by synchronizing with a mutex. This can be smarter with memory
barriers but let's go there if it actually turns out to be necessary.
Signed-off-by: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/g/533ABA32.9080602@oracle.com
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | fs/kernfs/inode.c | 14 |
1 files changed, 10 insertions, 4 deletions
diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c index e55126f85bd2..553946c9d952 100644 --- a/fs/kernfs/inode.c +++ b/fs/kernfs/inode.c @@ -48,14 +48,18 @@ void __init kernfs_inode_init(void) static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn) { + static DEFINE_MUTEX(iattr_mutex); + struct kernfs_iattrs *ret; struct iattr *iattrs; + mutex_lock(&iattr_mutex); + if (kn->iattr) - return kn->iattr; + goto out_unlock; kn->iattr = kzalloc(sizeof(struct kernfs_iattrs), GFP_KERNEL); if (!kn->iattr) - return NULL; + goto out_unlock; iattrs = &kn->iattr->ia_iattr; /* assign default attributes */ @@ -65,8 +69,10 @@ static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn) iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME; simple_xattrs_init(&kn->iattr->xattrs); - - return kn->iattr; +out_unlock: + ret = kn->iattr; + mutex_unlock(&iattr_mutex); + return ret; } static int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr) |