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cgroup: initialize xattr before calling d_instantiate() 

cgroup_create_file() calls d_instantiate(), which may decide to look
at the xattrs on the file. Smack always does this and SELinux can be
configured to do so.

But cgroup_add_file() didn't initialize xattrs before calling
cgroup_create_file(), which finally leads to dereferencing NULL
dentry->d_fsdata.

This bug has been there since cgroup xattr was introduced.

Cc: <stable@vger.kernel.org> # 3.8.x
Reported-by: Ivan Bulatovic <combuster@archlinux.us>
Reported-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Li Zefan 2013-05-14 19:44:20 +08:00 committed by Tejun Heo
parent f722406faa
commit d6cbf35dac
1 changed files with 5 additions and 4 deletions
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9
kernel/cgroup.c
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@ -2699,13 +2699,14 @@ static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
goto out;
}
cfe->type = (void *)cft;
cfe->dentry = dentry;
dentry->d_fsdata = cfe;
simple_xattrs_init(&cfe->xattrs);
mode = cgroup_file_mode(cft);
error = cgroup_create_file(dentry, mode | S_IFREG, cgrp->root->sb);
if (!error) {
cfe->type = (void *)cft;
cfe->dentry = dentry;
dentry->d_fsdata = cfe;
simple_xattrs_init(&cfe->xattrs);
list_add_tail(&cfe->node, &parent->files);
cfe = NULL;
}