Subject: CVE-2021-47341: KVM: mmio: Fix use-after-free Read in kvm_vm_ioctl_unregister_coalesced_mmio

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

KVM: mmio: Fix use-after-free Read in kvm_vm_ioctl_unregister_coalesced_mmio

BUG: KASAN: use-after-free in kvm_vm_ioctl_unregister_coalesced_mmio+0x7c/0x1ec arch/arm64/kvm/../../../virt/kvm/coalesced_mmio.c:183
Read of size 8 at addr ffff0000c03a2500 by task syz-executor083/4269

CPU: 5 PID: 4269 Comm: syz-executor083 Not tainted 5.10.0 #7
Hardware name: linux,dummy-virt (DT)
Call trace:
 dump_backtrace+0x0/0x2d0 arch/arm64/kernel/stacktrace.c:132
 show_stack+0x28/0x34 arch/arm64/kernel/stacktrace.c:196
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x110/0x164 lib/dump_stack.c:118
 print_address_description+0x78/0x5c8 mm/kasan/report.c:385
 __kasan_report mm/kasan/report.c:545 [inline]
 kasan_report+0x148/0x1e4 mm/kasan/report.c:562
 check_memory_region_inline mm/kasan/generic.c:183 [inline]
 __asan_load8+0xb4/0xbc mm/kasan/generic.c:252
 kvm_vm_ioctl_unregister_coalesced_mmio+0x7c/0x1ec arch/arm64/kvm/../../../virt/kvm/coalesced_mmio.c:183
 kvm_vm_ioctl+0xe30/0x14c4 arch/arm64/kvm/../../../virt/kvm/kvm_main.c:3755
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __arm64_sys_ioctl+0xf88/0x131c fs/ioctl.c:739
 __invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
 invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
 el0_svc_common arch/arm64/kernel/syscall.c:158 [inline]
 do_el0_svc+0x120/0x290 arch/arm64/kernel/syscall.c:220
 el0_svc+0x1c/0x28 arch/arm64/kernel/entry-common.c:367
 el0_sync_handler+0x98/0x170 arch/arm64/kernel/entry-common.c:383
 el0_sync+0x140/0x180 arch/arm64/kernel/entry.S:670

Allocated by task 4269:
 stack_trace_save+0x80/0xb8 kernel/stacktrace.c:121
 kasan_save_stack mm/kasan/common.c:48 [inline]
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc+0xdc/0x120 mm/kasan/common.c:461
 kasan_kmalloc+0xc/0x14 mm/kasan/common.c:475
 kmem_cache_alloc_trace include/linux/slab.h:450 [inline]
 kmalloc include/linux/slab.h:552 [inline]
 kzalloc include/linux/slab.h:664 [inline]
 kvm_vm_ioctl_register_coalesced_mmio+0x78/0x1cc arch/arm64/kvm/../../../virt/kvm/coalesced_mmio.c:146
 kvm_vm_ioctl+0x7e8/0x14c4 arch/arm64/kvm/../../../virt/kvm/kvm_main.c:3746
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __arm64_sys_ioctl+0xf88/0x131c fs/ioctl.c:739
 __invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
 invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
 el0_svc_common arch/arm64/kernel/syscall.c:158 [inline]
 do_el0_svc+0x120/0x290 arch/arm64/kernel/syscall.c:220
 el0_svc+0x1c/0x28 arch/arm64/kernel/entry-common.c:367
 el0_sync_handler+0x98/0x170 arch/arm64/kernel/entry-common.c:383
 el0_sync+0x140/0x180 arch/arm64/kernel/entry.S:670

Freed by task 4269:
 stack_trace_save+0x80/0xb8 kernel/stacktrace.c:121
 kasan_save_stack mm/kasan/common.c:48 [inline]
 kasan_set_track+0x38/0x6c mm/kasan/common.c:56
 kasan_set_free_info+0x20/0x40 mm/kasan/generic.c:355
 __kasan_slab_free+0x124/0x150 mm/kasan/common.c:422
 kasan_slab_free+0x10/0x1c mm/kasan/common.c:431
 slab_free_hook mm/slub.c:1544 [inline]
 slab_free_freelist_hook mm/slub.c:1577 [inline]
 slab_free mm/slub.c:3142 [inline]
 kfree+0x104/0x38c mm/slub.c:4124
 coalesced_mmio_destructor+0x94/0xa4 arch/arm64/kvm/../../../virt/kvm/coalesced_mmio.c:102
 kvm_iodevice_destructor include/kvm/iodev.h:61 [inline]
 kvm_io_bus_unregister_dev+0x248/0x280 arch/arm64/kvm/../../../virt/kvm/kvm_main.c:4374
 kvm_vm_ioctl_unregister_coalesced_mmio+0x158/0x1ec arch/arm64/kvm/../../../virt/kvm/coalesced_mmio.c:186
 kvm_vm_ioctl+0xe30/0x14c4 arch/arm64/kvm/../../../virt/kvm/kvm_main.c:3755
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl fs/ioctl.c:739 [inline]
 __arm64_sys_ioctl+0xf88/0x131c fs/ioctl.c:739
 __invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
 invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
 el0_svc_common arch/arm64/kernel/syscall.c:158 [inline]
 do_el0_svc+0x120/0x290 arch/arm64/kernel/syscall.c:220
 el0_svc+0x1c/0x28 arch/arm64/kernel/entry-common.c:367
 el0_sync_handler+0x98/0x170 arch/arm64/kernel/entry-common.c:383
 el0_sync+0x140/0x180 arch/arm64/kernel/entry.S:670

If kvm_io_bus_unregister_dev() return -ENOMEM, we already call kvm_iodevice_destructor()
inside this function to delete 'struct kvm_coalesced_mmio_dev *dev' from list
and free the dev, but kvm_iodevice_destructor() is called again, it will lead
the above issue.

Let's check the the return value of kvm_io_bus_unregister_dev(), only call
kvm_iodevice_destructor() if the return value is 0.

The Linux kernel CVE team has assigned CVE-2021-47341 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.4.119 with commit 7d1bc32d6477 and fixed in 5.4.134 with commit f2ff9d03432f
	Issue introduced in 5.10.37 with commit 2a20592baff5 and fixed in 5.10.52 with commit 679837dc0aba
	Issue introduced in 5.12.4 with commit 50cbad42bfea and fixed in 5.12.19 with commit 8d7c539316d6
	Issue introduced in 5.13 with commit 5d3c4c79384a and fixed in 5.13.4 with commit 069d44a24c0f
	Issue introduced in 5.13 with commit 5d3c4c79384a and fixed in 5.14 with commit 23fa2e46a555
	Issue introduced in 5.11.21 with commit 168e82f640ed

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2021-47341
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	virt/kvm/coalesced_mmio.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/f2ff9d03432fcb160e9f7d4be26174d89de2779a
	https://git.kernel.org/stable/c/679837dc0abaa2c6e2a7bcd86483e05eee1d5066
	https://git.kernel.org/stable/c/8d7c539316d652d217e5e82b89ee204c812a7061
	https://git.kernel.org/stable/c/069d44a24c0ff8f85adf49233aae7a8ca16f5c7e
	https://git.kernel.org/stable/c/23fa2e46a5556f787ce2ea1a315d3ab93cced204