From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock Add a sleepable verifier test that loads a graph-node local kptr in an explicit RCU read-side critical section, then passes its node to bpf_rbtree_remove() after the section ends. Before the verifier fix, the stale NON_OWN_REF flag makes the node look like a live borrowed reference and the program is accepted. After the fix, the pointer is demoted without NON_OWN_REF and the graph kfunc argument is rejected. Also exercise a graph kptr loaded while a spin lock provides implicit RCU protection. The pointer must be invalidated when the lock is released, which guards the required ordering between non-owning-reference invalidation and RCU demotion. Update the existing fault-protected load test state description. The post-unlock pointer no longer carries NON_OWN_REF, but remains readable because the load is rewritten to use BPF_PROBE_MEM. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- arch/mips/kvm/hypcall.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+) create mode 100644 arch/mips/kvm/hypcall.c (limited to 'arch/mips/kvm/hypcall.c') diff --git a/arch/mips/kvm/hypcall.c b/arch/mips/kvm/hypcall.c new file mode 100644 index 000000000..830634351 --- /dev/null +++ b/arch/mips/kvm/hypcall.c @@ -0,0 +1,53 @@ +/* + * This file is subject to the terms and conditions of the GNU General Public + * License. See the file "COPYING" in the main directory of this archive + * for more details. + * + * KVM/MIPS: Hypercall handling. + * + * Copyright (C) 2015 Imagination Technologies Ltd. + */ + +#include +#include +#include + +#define MAX_HYPCALL_ARGS 4 + +enum emulation_result kvm_mips_emul_hypcall(struct kvm_vcpu *vcpu, + union mips_instruction inst) +{ + unsigned int code = (inst.co_format.code >> 5) & 0x3ff; + + kvm_debug("[%#lx] HYPCALL %#03x\n", vcpu->arch.pc, code); + + switch (code) { + case 0: + return EMULATE_HYPERCALL; + default: + return EMULATE_FAIL; + }; +} + +static int kvm_mips_hypercall(struct kvm_vcpu *vcpu, unsigned long num, + const unsigned long *args, unsigned long *hret) +{ + /* Report unimplemented hypercall to guest */ + *hret = -KVM_ENOSYS; + return RESUME_GUEST; +} + +int kvm_mips_handle_hypcall(struct kvm_vcpu *vcpu) +{ + unsigned long num, args[MAX_HYPCALL_ARGS]; + + /* read hypcall number and arguments */ + num = vcpu->arch.gprs[2]; /* v0 */ + args[0] = vcpu->arch.gprs[4]; /* a0 */ + args[1] = vcpu->arch.gprs[5]; /* a1 */ + args[2] = vcpu->arch.gprs[6]; /* a2 */ + args[3] = vcpu->arch.gprs[7]; /* a3 */ + + return kvm_mips_hypercall(vcpu, num, + args, &vcpu->arch.gprs[2] /* v0 */); +} -- cgit v1.3.1