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KASAN detects a use-after-free when vop devices are removed. This problem was introduced by commit0063e8bbd2("virtio_vop: don't kfree device on register failure"). That patch moved the freeing of the struct _vop_vdev to the release function, but failed to ensure that vop holds a reference to the device when it doesn't want it to go away. A kfree() was replaced with a put_device() in the unregistration path, but the last reference to the device is already dropped in unregister_virtio_device() so the struct is freed before vop is done with it. Fix it by holding a reference until cleanup is done. This is similar to the fix in virtio_pci in commit2989be09a8("virtio_pci: fix use after free on release"). ================================================================== BUG: KASAN: use-after-free in vop_scan_devices+0xc6c/0xe50 [vop] Read of size 8 at addr ffff88800da18580 by task kworker/0:1/12 CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 5.0.0-rc4+ #53 Workqueue: events vop_hotplug_devices [vop] Call Trace: dump_stack+0x74/0xbb print_address_description+0x5d/0x2b0 ? vop_scan_devices+0xc6c/0xe50 [vop] kasan_report+0x152/0x1aa ? vop_scan_devices+0xc6c/0xe50 [vop] ? vop_scan_devices+0xc6c/0xe50 [vop] vop_scan_devices+0xc6c/0xe50 [vop] ? vop_loopback_free_irq+0x160/0x160 [vop_loopback] process_one_work+0x7c0/0x14b0 ? pwq_dec_nr_in_flight+0x2d0/0x2d0 ? do_raw_spin_lock+0x120/0x280 worker_thread+0x8f/0xbf0 ? __kthread_parkme+0x78/0xf0 ? process_one_work+0x14b0/0x14b0 kthread+0x2ae/0x3a0 ? kthread_park+0x120/0x120 ret_from_fork+0x3a/0x50 Allocated by task 12: kmem_cache_alloc_trace+0x13a/0x2a0 vop_scan_devices+0x473/0xe50 [vop] process_one_work+0x7c0/0x14b0 worker_thread+0x8f/0xbf0 kthread+0x2ae/0x3a0 ret_from_fork+0x3a/0x50 Freed by task 12: kfree+0x104/0x310 device_release+0x73/0x1d0 kobject_put+0x14f/0x420 unregister_virtio_device+0x32/0x50 vop_scan_devices+0x19d/0xe50 [vop] process_one_work+0x7c0/0x14b0 worker_thread+0x8f/0xbf0 kthread+0x2ae/0x3a0 ret_from_fork+0x3a/0x50 The buggy address belongs to the object at ffff88800da18008 which belongs to the cache kmalloc-2k of size 2048 The buggy address is located 1400 bytes inside of 2048-byte region [ffff88800da18008, ffff88800da18808) The buggy address belongs to the page: page:ffffea0000368600 count:1 mapcount:0 mapping:ffff88801440dbc0 index:0x0 compound_mapcount: 0 flags: 0x4000000000010200(slab|head) raw: 4000000000010200 ffffea0000378608 ffffea000037a008 ffff88801440dbc0 raw: 0000000000000000 00000000000d000d 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff88800da18480: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88800da18500: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff88800da18580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff88800da18600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff88800da18680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== Fixes:0063e8bbd2("virtio_vop: don't kfree device on register failure") Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com> Cc: stable <stable@vger.kernel.org> 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.