mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-07 13:57:54 -04:00
ae8f8b3761
Alex reports that syzkaller has managed to trigger a use-after-free when
tearing down a VM:
BUG: KASAN: slab-use-after-free in kvm_put_kvm+0x300/0xe68 virt/kvm/kvm_main.c:5769
Read of size 8 at addr ffffff801c6890d0 by task syz.3.2219/10758
CPU: 3 UID: 0 PID: 10758 Comm: syz.3.2219 Not tainted 6.11.0-rc6-dirty #64
Hardware name: linux,dummy-virt (DT)
Call trace:
dump_backtrace+0x17c/0x1a8 arch/arm64/kernel/stacktrace.c:317
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:324
__dump_stack lib/dump_stack.c:93 [inline]
dump_stack_lvl+0x94/0xc0 lib/dump_stack.c:119
print_report+0x144/0x7a4 mm/kasan/report.c:377
kasan_report+0xcc/0x128 mm/kasan/report.c:601
__asan_report_load8_noabort+0x20/0x2c mm/kasan/report_generic.c:381
kvm_put_kvm+0x300/0xe68 virt/kvm/kvm_main.c:5769
kvm_vm_release+0x4c/0x60 virt/kvm/kvm_main.c:1409
__fput+0x198/0x71c fs/file_table.c:422
____fput+0x20/0x30 fs/file_table.c:450
task_work_run+0x1cc/0x23c kernel/task_work.c:228
do_notify_resume+0x144/0x1a0 include/linux/resume_user_mode.h:50
el0_svc+0x64/0x68 arch/arm64/kernel/entry-common.c:169
el0t_64_sync_handler+0x90/0xfc arch/arm64/kernel/entry-common.c:730
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598
Upon closer inspection, it appears that we do not properly tear down the
MMIO registration for a vCPU that fails creation late in the game, e.g.
a vCPU w/ the same ID already exists in the VM.
It is important to consider the context of commit that introduced this bug
by moving the unregistration out of __kvm_vgic_vcpu_destroy(). That
change correctly sought to avoid an srcu v. config_lock inversion by
breaking up the vCPU teardown into two parts, one guarded by the
config_lock.
Fix the use-after-free while avoiding lock inversion by adding a
special-cased unregistration to __kvm_vgic_vcpu_destroy(). This is safe
because failed vCPUs are torn down outside of the config_lock.
Cc: stable@vger.kernel.org
Fixes: f616506754 ("KVM: arm64: vgic: Don't hold config_lock while unregistering redistributors")
Reported-by: Alexander Potapenko <glider@google.com>
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20241007223909.2157336-1-oliver.upton@linux.dev
Signed-off-by: Marc Zyngier <maz@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 reStructuredText 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.