On Thu, 5 Nov 2020 14:47:13 +0100
Cédric Le Goater <clg@xxxxxxxx> wrote:
> When accessing the ESB page of a source interrupt, the fault handler
> will retrieve the page address from the XIVE interrupt 'xive_irq_data'
> structure. If the associated KVM XIVE interrupt is not valid, that is
> not allocated at the HW level for some reason, the fault handler will
> dereference a NULL pointer leading to the oops below :
>
> WARNING: CPU: 40 PID: 59101 at arch/powerpc/kvm/book3s_xive_native.c:259 xive_native_esb_fault+0xe4/0x240 [kvm]
> CPU: 40 PID: 59101 Comm: qemu-system-ppc Kdump: loaded Tainted: G W --------- - - 4.18.0-240.el8.ppc64le #1
> NIP: c00800000e949fac LR: c00000000044b164 CTR: c00800000e949ec8
> REGS: c000001f69617840 TRAP: 0700 Tainted: G W --------- - - (4.18.0-240.el8.ppc64le)
> MSR: 9000000000029033 <SF,HV,EE,ME,IR,DR,RI,LE> CR: 44044282 XER: 00000000
> CFAR: c00000000044b160 IRQMASK: 0
> GPR00: c00000000044b164 c000001f69617ac0 c00800000e96e000 c000001f69617c10
> GPR04: 05faa2b21e000080 0000000000000000 0000000000000005 ffffffffffffffff
> GPR08: 0000000000000000 0000000000000001 0000000000000000 0000000000000001
> GPR12: c00800000e949ec8 c000001ffffd3400 0000000000000000 0000000000000000
> GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> GPR20: 0000000000000000 0000000000000000 c000001f5c065160 c000000001c76f90
> GPR24: c000001f06f20000 c000001f5c065100 0000000000000008 c000001f0eb98c78
> GPR28: c000001dcab40000 c000001dcab403d8 c000001f69617c10 0000000000000011
> NIP [c00800000e949fac] xive_native_esb_fault+0xe4/0x240 [kvm]
> LR [c00000000044b164] __do_fault+0x64/0x220
> Call Trace:
> [c000001f69617ac0] [0000000137a5dc20] 0x137a5dc20 (unreliable)
> [c000001f69617b50] [c00000000044b164] __do_fault+0x64/0x220
> [c000001f69617b90] [c000000000453838] do_fault+0x218/0x930
> [c000001f69617bf0] [c000000000456f50] __handle_mm_fault+0x350/0xdf0
> [c000001f69617cd0] [c000000000457b1c] handle_mm_fault+0x12c/0x310
> [c000001f69617d10] [c00000000007ef44] __do_page_fault+0x264/0xbb0
> [c000001f69617df0] [c00000000007f8c8] do_page_fault+0x38/0xd0
> [c000001f69617e30] [c00000000000a714] handle_page_fault+0x18/0x38
> Instruction dump:
> 40c2fff0 7c2004ac 2fa90000 409e0118 73e90001 41820080 e8bd0008 7c2004ac
> 7ca90074 39400000 915c0000 7929d182 <0b090000> 2fa50000 419e0080 e89e0018
> ---[ end trace 66c6ff034c53f64f ]---
> xive-kvm: xive_native_esb_fault: accessing invalid ESB page for source 8 !
>
> Fix that by checking the validity of the KVM XIVE interrupt structure.
>
> Reported-by: Greg Kurz <groug@xxxxxxxx>
> Signed-off-by: Cédric Le Goater <clg@xxxxxxxx>
> ---
Looks sane to me. QEMU still crashes on SIGBUS but no more oops at least.
Tested-by: Greg Kurz <groug@xxxxxxxx>
> arch/powerpc/kvm/book3s_xive_native.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c
> index d0c2db0e07fa..a59a94f02733 100644
> --- a/arch/powerpc/kvm/book3s_xive_native.c
> +++ b/arch/powerpc/kvm/book3s_xive_native.c
> @@ -251,6 +251,13 @@ static vm_fault_t xive_native_esb_fault(struct vm_fault *vmf)
> }
>
> state = &sb->irq_state[src];
> +
> + /* Some sanity checking */
> + if (!state->valid) {
> + pr_devel("%s: source %lx invalid !\n", __func__, irq);
> + return VM_FAULT_SIGBUS;
> + }
> +
> kvmppc_xive_select_irq(state, &hw_num, &xd);
>
> arch_spin_lock(&sb->lock);
