3.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Li Zefan <lizefan@xxxxxxxxxx>
commit d6cbf35dac8a3dadb9103379820c96d7c85df3d9 upstream.
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.
Reported-by: Ivan Bulatovic <combuster@xxxxxxxxxxxx>
Reported-by: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/cgroup.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2747,13 +2747,14 @@ static int cgroup_add_file(struct cgroup
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;
}
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