locks: use file_inode()

Orabug: 25308036

[ Upstream commit 6343a2120862f7023006c8091ad95c1f16a32077 ]

(Another one for the f_path debacle.)

ltp fcntl33 testcase caused an Oops in selinux_file_send_sigiotask.

The reason is that generic_add_lease() used filp->f_path.dentry->inode
while all the others use file_inode().  This makes a difference for files
opened on overlayfs since the former will point to the overlay inode the
latter to the underlying inode.

So generic_add_lease() added the lease to the overlay inode and
generic_delete_lease() removed it from the underlying inode.  When the file
was released the lease remained on the overlay inode's lock list, resulting
in use after free.

Reported-by: Eryu Guan <eguan@redhat.com>
Fixes: 4bacc9c9234c ("overlayfs: Make f_path always point to the overlay and f_inode to the underlay")
Cc: <stable@vger.kernel.org>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit a1f678e55da552523dd45a531580a7e533b3bd8f)
Signed-off-by: Dhaval Giani <dhaval.giani@oracle.com>

diff --git a/fs/locks.c b/fs/locks.c
index 8501eecb2af0ccb12ab56042483e3587fd48cba4..3c234b9fbdd98e2db6f013efe41064dff5e05bd7 100644 (file)
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1596,7 +1596,7 @@ generic_add_lease(struct file *filp, long arg, struct file_lock **flp, void **pr
 {
        struct file_lock *fl, *my_fl = NULL, *lease;
        struct dentry *dentry = filp->f_path.dentry;
-       struct inode *inode = dentry->d_inode;
+       struct inode *inode = file_inode(filp);
        struct file_lock_context *ctx;
        bool is_deleg = (*flp)->fl_flags & FL_DELEG;
        int error;