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authorTejun Heo <tj@kernel.org>2014-04-02 16:40:52 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-04-26 17:19:04 -0700
commit29b311867df2f1f7aee9ec42517becbbb4aeeeef (patch)
parent52d6c48c9db5b020e6595067a7f1b00562d26434 (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>
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;
- return kn->iattr;
+ ret = kn->iattr;
+ mutex_unlock(&iattr_mutex);
+ return ret;
static int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)