diff options
| author | Pavel Shilovsky <pshilov@microsoft.com> | 2019-11-27 16:18:39 -0800 |
|---|---|---|
| committer | Steve French <stfrench@microsoft.com> | 2019-12-02 15:15:00 -0600 |
| commit | 6f582b273ec23332074d970a7fb25bef835df71f (patch) | |
| tree | dde3c85d4586e46485cb03fdf5730afbbf82529c | |
| parent | 21b26d2679584c6a60e861aa3e5ca09a6bab0633 (diff) | |
CIFS: Fix NULL-pointer dereference in smb2_push_mandatory_locks
Currently when the client creates a cifsFileInfo structure for
a newly opened file, it allocates a list of byte-range locks
with a pointer to the new cfile and attaches this list to the
inode's lock list. The latter happens before initializing all
other fields, e.g. cfile->tlink. Thus a partially initialized
cifsFileInfo structure becomes available to other threads that
walk through the inode's lock list. One example of such a thread
may be an oplock break worker thread that tries to push all
cached byte-range locks. This causes NULL-pointer dereference
in smb2_push_mandatory_locks() when accessing cfile->tlink:
[598428.945633] BUG: kernel NULL pointer dereference, address: 0000000000000038
...
[598428.945749] Workqueue: cifsoplockd cifs_oplock_break [cifs]
[598428.945793] RIP: 0010:smb2_push_mandatory_locks+0xd6/0x5a0 [cifs]
...
[598428.945834] Call Trace:
[598428.945870] ? cifs_revalidate_mapping+0x45/0x90 [cifs]
[598428.945901] cifs_oplock_break+0x13d/0x450 [cifs]
[598428.945909] process_one_work+0x1db/0x380
[598428.945914] worker_thread+0x4d/0x400
[598428.945921] kthread+0x104/0x140
[598428.945925] ? process_one_work+0x380/0x380
[598428.945931] ? kthread_park+0x80/0x80
[598428.945937] ret_from_fork+0x35/0x40
Fix this by reordering initialization steps of the cifsFileInfo
structure: initialize all the fields first and then add the new
byte-range lock list to the inode's lock list.
Cc: Stable <stable@vger.kernel.org>
Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
| -rw-r--r-- | fs/cifs/file.c | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/fs/cifs/file.c b/fs/cifs/file.c index f1fe9c44d298..9ae41042fa3d 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -315,9 +315,6 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file, INIT_LIST_HEAD(&fdlocks->locks); fdlocks->cfile = cfile; cfile->llist = fdlocks; - cifs_down_write(&cinode->lock_sem); - list_add(&fdlocks->llist, &cinode->llist); - up_write(&cinode->lock_sem); cfile->count = 1; cfile->pid = current->tgid; @@ -342,6 +339,10 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file, oplock = 0; } + cifs_down_write(&cinode->lock_sem); + list_add(&fdlocks->llist, &cinode->llist); + up_write(&cinode->lock_sem); + spin_lock(&tcon->open_file_lock); if (fid->pending_open->oplock != CIFS_OPLOCK_NO_CHANGE && oplock) oplock = fid->pending_open->oplock; |