From 8e1858710d9a71d88acd922f2e95d1eddb90eea0 Mon Sep 17 00:00:00 2001 From: Xiubo Li Date: Thu, 17 Nov 2022 10:57:53 +0800 Subject: [PATCH] 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: Xiubo Li Reviewed-by: Jeff Layton Reviewed-by: Ilya Dryomov Signed-off-by: Ilya Dryomov --- fs/ceph/locks.c | 20 ++++++++++++++++++-- include/linux/fs.h | 3 +++ 2 files changed, 21 insertions(+), 2 deletions(-) diff --git a/fs/ceph/locks.c b/fs/ceph/locks.c index 6b3b8c299c17..9c8dc8a55e7e 100644 --- a/fs/ceph/locks.c +++ b/fs/ceph/locks.c @@ -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 = { diff --git a/include/linux/fs.h b/include/linux/fs.h index 066555ad1bf8..c1769a2c5d70 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -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; -- 2.11.0