In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
RISC-V: KVM: Synchronize hrtimer callback during teardown<\/p>\n
The non-Sstc hrtimer callback clears next_set before its final uses of
\nthe enclosing vCPU. If teardown observes next_set as false while the
\ncallback is still running, kvm_riscv_vcpu_timer_cancel() skips
\nhrtimer_cancel() and kvm_destroy_vcpus() can free the vCPU before the
\ncallback enters kvm_riscv_vcpu_set_interrupt().<\/p>\n
A guest can arm the timer with SBI TIME and request shutdown with SBI
\nlegacy shutdown or SRST. A VMM that honors KVM_EXIT_SYSTEM_EVENT and
\ndestroys the VM supplies the teardown side of the race; no post-launch
\nhost ioctl is needed to arm or request teardown.<\/p>\n
On upstream master 62cc90241548, generic KASAN reported:<\/p>\n
BUG: KASAN: slab-use-after-free in do_raw_spin_lock
\n Write of size 4 at addr ff60000005e58898<\/p>\n
kvm_riscv_vcpu_set_interrupt
\n kvm_riscv_vcpu_hrtimer_expired
\n __hrtimer_run_queues
\n hrtimer_interrupt<\/p>\n
The object was allocated by KVM_CREATE_VCPU and freed concurrently by:<\/p>\n
kvm_destroy_vcpus
\n kvm_arch_destroy_vm
\n kvm_destroy_vm
\n __fput<\/p>\n
For deterministic validation, I added mdelay(1000) immediately after
\nthe existing next_set = false assignment. This only widens the
\nexisting post-clear callback window. A no-delay trace build naturally
\nreached the callback-after-teardown-start\/before-deinit ordering in 12
\nof 200 runs, but 1,500 stock-kernel stress iterations did not produce a
\nKASAN report, so natural reproduction is timing-sensitive.<\/p>\n
Always invoke hrtimer_cancel() for an initialized timer. Preserve the
\nexisting -EINVAL result when the timer is no longer set, but only after
\nsynchronizing with a running callback.<\/p>\n
With this patch, hrtimer_cancel() blocked for the full widened callback
\nwindow before vCPU destruction. KASAN reported no error in 100
\nfixed-and-widened runs or 200 fix-only timing-sweep runs.<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
RISC-V: KVM: Synchronize hrtimer callback during teardown<\/p>\n
The non-Sstc hrtimer callback clears next_set before its final uses of
\nt<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-40936","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/40936","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=40936"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=40936"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=40936"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}