The virtual-mode HPT hcall handlers (H_ENTER, H_REMOVE, H_BULK_REMOVE, H_CLEAR_REF, H_CLEAR_MOD) call into book3s_hv_rm_mmu.c, which accesses memslots via kvm_memslots_raw(). kvm_memslots_raw() uses rcu_dereference_raw_check() to bypass SRCU lockdep annotation checking. This is safe in real mode because the entire guest entry/exit is wrapped in srcu_read_lock/unlock inside kvmppc_run_core() and kvmhv_run_single_vcpu(). However, since commit 6165d5dd99db ("KVM: PPC: Book3S HV: add virtual mode handlers for HPT hcalls and page faults"), these same handlers are also executed in virtual mode via kvmppc_pseries_do_hcall(), which runs after SRCU has already been released on guest exit. A concurrent KVM_SET_USER_MEMORY_REGION deletion or move can therefore call synchronize_srcu_expedited() — which does not wait for this thread — and then kfree(slot) and vfree(slot->arch.rmap) while the hcall handler still holds a raw pointer to the memslot. lock_rmap() then writes to freed vmalloc memory, leading to use-after-free and memory corruption. Because kvm_memslots_raw() suppresses lockdep checks, this race is entirely silent. Fix this by factoring out the 7 HPT hcall handlers (H_REMOVE, H_ENTER, H_READ, H_CLEAR_MOD, H_CLEAR_REF, H_PROTECT, H_BULK_REMOVE) into a helper function, kvmppc_pseries_do_hpt_hcall(), and wrapping its call site in srcu_read_lock(&kvm->srcu) / srcu_read_unlock(&kvm->srcu, idx). Targeting only the HPT hcalls avoids wrapping non-HPT hcalls that sleep (such as H_CONFER, H_REGISTER_VPA, H_PAGE_INIT) or handlers that already acquire SRCU internally (such as H_RTAS). Fixes: 6165d5dd99db ("KVM: PPC: Book3S HV: add virtual mode handlers for HPT hcalls and page faults") Cc: stable@vger.kernel.org # v5.14+ Suggested-by: Ritesh Harjani (IBM) Reviewed-by: Ritesh Harjani (IBM) Signed-off-by: Amit Machhiwal --- arch/powerpc/kvm/book3s_hv.c | 70 ++++++++++++++++++------------------ 1 file changed, 35 insertions(+), 35 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index de05d721edc4..46dd550115a4 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -1159,6 +1159,38 @@ static long kvmppc_h_rpt_invalidate(struct kvm_vcpu *vcpu, return H_SUCCESS; } +static long kvmppc_pseries_do_hpt_hcall(struct kvm_vcpu *vcpu, unsigned long req) +{ + switch (req) { + case H_REMOVE: + return kvmppc_h_remove(vcpu, kvmppc_get_gpr(vcpu, 4), + kvmppc_get_gpr(vcpu, 5), + kvmppc_get_gpr(vcpu, 6)); + case H_ENTER: + return kvmppc_h_enter(vcpu, kvmppc_get_gpr(vcpu, 4), + kvmppc_get_gpr(vcpu, 5), + kvmppc_get_gpr(vcpu, 6), + kvmppc_get_gpr(vcpu, 7)); + case H_READ: + return kvmppc_h_read(vcpu, kvmppc_get_gpr(vcpu, 4), + kvmppc_get_gpr(vcpu, 5)); + case H_CLEAR_MOD: + return kvmppc_h_clear_mod(vcpu, kvmppc_get_gpr(vcpu, 4), + kvmppc_get_gpr(vcpu, 5)); + case H_CLEAR_REF: + return kvmppc_h_clear_ref(vcpu, kvmppc_get_gpr(vcpu, 4), + kvmppc_get_gpr(vcpu, 5)); + case H_PROTECT: + return kvmppc_h_protect(vcpu, kvmppc_get_gpr(vcpu, 4), + kvmppc_get_gpr(vcpu, 5), + kvmppc_get_gpr(vcpu, 6)); + case H_BULK_REMOVE: + return kvmppc_h_bulk_remove(vcpu); + } + + return H_FUNCTION; +} + int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu) { struct kvm *kvm = vcpu->kvm; @@ -1174,47 +1206,15 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu) switch (req) { case H_REMOVE: - ret = kvmppc_h_remove(vcpu, kvmppc_get_gpr(vcpu, 4), - kvmppc_get_gpr(vcpu, 5), - kvmppc_get_gpr(vcpu, 6)); - if (ret == H_TOO_HARD) - return RESUME_HOST; - break; case H_ENTER: - ret = kvmppc_h_enter(vcpu, kvmppc_get_gpr(vcpu, 4), - kvmppc_get_gpr(vcpu, 5), - kvmppc_get_gpr(vcpu, 6), - kvmppc_get_gpr(vcpu, 7)); - if (ret == H_TOO_HARD) - return RESUME_HOST; - break; case H_READ: - ret = kvmppc_h_read(vcpu, kvmppc_get_gpr(vcpu, 4), - kvmppc_get_gpr(vcpu, 5)); - if (ret == H_TOO_HARD) - return RESUME_HOST; - break; case H_CLEAR_MOD: - ret = kvmppc_h_clear_mod(vcpu, kvmppc_get_gpr(vcpu, 4), - kvmppc_get_gpr(vcpu, 5)); - if (ret == H_TOO_HARD) - return RESUME_HOST; - break; case H_CLEAR_REF: - ret = kvmppc_h_clear_ref(vcpu, kvmppc_get_gpr(vcpu, 4), - kvmppc_get_gpr(vcpu, 5)); - if (ret == H_TOO_HARD) - return RESUME_HOST; - break; case H_PROTECT: - ret = kvmppc_h_protect(vcpu, kvmppc_get_gpr(vcpu, 4), - kvmppc_get_gpr(vcpu, 5), - kvmppc_get_gpr(vcpu, 6)); - if (ret == H_TOO_HARD) - return RESUME_HOST; - break; case H_BULK_REMOVE: - ret = kvmppc_h_bulk_remove(vcpu); + idx = srcu_read_lock(&kvm->srcu); + ret = kvmppc_pseries_do_hpt_hcall(vcpu, req); + srcu_read_unlock(&kvm->srcu, idx); if (ret == H_TOO_HARD) return RESUME_HOST; break; -- 2.54.0 (Apple Git-157)