ee4f281989
commit 6f582b273ec23332074d970a7fb25bef835df71f upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.