3.14-stable review patch. If anyone has any objections, please let me know.
------------------ From: Tejun Heo <t...@kernel.org> 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 <t...@kernel.org> Link: http://lkml.kernel.org/g/533aba32.9080...@oracle.com Reported-by: Sasha Levin <sasha.le...@oracle.com> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- fs/kernfs/inode.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) --- 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_iatt 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) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
