3e45352259
If md_run() fails after ->active_io is initialized, then percpu_ref_exit is called in error path. However, later md_free_disk will call percpu_ref_exit again which leads to a panic because of null pointer dereference. It can also trigger this bug when resources are initialized but are freed in error path, then will be freed again in md_free_disk. BUG: kernel NULL pointer dereference, address: 0000000000000038 Oops: 0000 [#1] PREEMPT SMP Workqueue: md_misc mddev_delayed_delete RIP: 0010:free_percpu+0x110/0x630 Call Trace: <TASK> __percpu_ref_exit+0x44/0x70 percpu_ref_exit+0x16/0x90 md_free_disk+0x2f/0x80 disk_release+0x101/0x180 device_release+0x84/0x110 kobject_put+0x12a/0x380 kobject_put+0x160/0x380 mddev_delayed_delete+0x19/0x30 process_one_work+0x269/0x680 worker_thread+0x266/0x640 kthread+0x151/0x1b0 ret_from_fork+0x1f/0x30 For creating raid device, md raid calls do_md_run->md_run, dm raid calls md_run. We alloc those memory in md_run. For stopping raid device, md raid calls do_md_stop->__md_stop, dm raid calls md_stop->__md_stop. So we can free those memory resources in __md_stop. Fixes: 72adae23a72c ("md: Change active_io to percpu") Reported-and-tested-by: Yu Kuai <yukuai3@huawei.com> Signed-off-by: Xiao Ni <xni@redhat.com> Signed-off-by: Song Liu <song@kernel.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.