Commit 8e185871 authored by Xiubo Li's avatar Xiubo Li Committed by Ilya Dryomov
Browse files

ceph: avoid use-after-free in ceph_fl_release_lock() 

When ceph releasing the file_lock it will try to get the inode pointer
from the fl->fl_file, which the memory could already be released by
another thread in filp_close(). Because in VFS layer the fl->fl_file
doesn't increase the file's reference counter.

Will switch to use ceph dedicate lock info to track the inode.

And in ceph_fl_release_lock() we should skip all the operations if the
fl->fl_u.ceph.inode is not set, which should come from the request
file_lock. And we will set fl->fl_u.ceph.inode when inserting it to the
inode lock list, which is when copying the lock.

Link: https://tracker.ceph.com/issues/57986


Signed-off-by: default avatarXiubo Li <xiubli@redhat.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Reviewed-by: default avatarIlya Dryomov <idryomov@gmail.com>
Signed-off-by: default avatarIlya Dryomov <idryomov@gmail.com>
parent 461ab10e

fs/ceph/locks.c

+18 −2
Original line number Diff line number Diff line
@@ -34,18 +34,34 @@ static void ceph_fl_copy_lock(struct file_lock *dst, struct file_lock *src) 
{

	struct inode *inode = file_inode(dst->fl_file);

	atomic_inc(&ceph_inode(inode)->i_filelock_ref);

	dst->fl_u.ceph.inode = igrab(inode);

}



/*

 * Do not use the 'fl->fl_file' in release function, which

 * is possibly already released by another thread.

 */

static void ceph_fl_release_lock(struct file_lock *fl)

{

	struct inode *inode = file_inode(fl->fl_file);

	struct ceph_inode_info *ci = ceph_inode(inode);

	struct inode *inode = fl->fl_u.ceph.inode;

	struct ceph_inode_info *ci;



	/*

	 * If inode is NULL it should be a request file_lock,

	 * nothing we can do.

	 */

	if (!inode)

		return;



	ci = ceph_inode(inode);

	if (atomic_dec_and_test(&ci->i_filelock_ref)) {

		/* clear error when all locks are released */

		spin_lock(&ci->i_ceph_lock);

		ci->i_ceph_flags &= ~CEPH_I_ERROR_FILELOCK;

		spin_unlock(&ci->i_ceph_lock);

	}

	fl->fl_u.ceph.inode = NULL;

	iput(inode);

}



static const struct file_lock_operations ceph_fl_lock_ops = {

include/linux/fs.h

+3 −0
Original line number Diff line number Diff line
@@ -1119,6 +1119,9 @@ struct file_lock { 
			int state;		/* state of grant or error if -ve */

			unsigned int	debug_id;

		} afs;

		struct {

			struct inode *inode;

		} ceph;

	} fl_u;

} __randomize_layout;