* [PATCH] irqchip/gic-v4: Harden against bogus command line @ 2026-05-21 13:05 Mostafa Saleh 2026-05-23 9:53 ` Marc Zyngier 0 siblings, 1 reply; 4+ messages in thread From: Mostafa Saleh @ 2026-05-21 13:05 UTC (permalink / raw) To: linux-arm-kernel, linux-kernel; +Cc: maz, tglx, Mostafa Saleh When accidentally setting “kvm-arm.vgic_v4_enable=1” on the wrong setup that has no MSI controller device tree node (it exists but not used) and GICv4, it caused a panic as “gic_domain” is NULL and the kernel attempted to access its ops. Originally, I hit this on an older kernel, but was able to reproduce it on upstream with Qemu by hacking this unreasonable setup. [ 33.145536] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000028 [ 33.145658] Mem abort info: [ 33.145751] ESR = 0x0000000096000006 ... [ 33.154057] CPU: 1 UID: 0 PID: 295 Comm: lkvm-static Not tainted 7.1.0-rc4-ge3f15ad3970e #5 PREEMPT [ 33.156922] Hardware name: linux,dummy-virt (DT) [ 33.158780] pstate: 81402005 (Nzcv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) [ 33.160340] pc : __irq_domain_instantiate+0x1d4/0x578 [ 33.162602] lr : __irq_domain_instantiate+0x1cc/0x578 Add a hardening check to avoid the NULL access, and fail the VM creation in that case. Signed-off-by: Mostafa Saleh <smostafa@google.com> --- drivers/irqchip/irq-gic-v4.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/irqchip/irq-gic-v4.c b/drivers/irqchip/irq-gic-v4.c index 8455b4a5fbb0..7e39f7eae85f 100644 --- a/drivers/irqchip/irq-gic-v4.c +++ b/drivers/irqchip/irq-gic-v4.c @@ -159,6 +159,9 @@ int its_alloc_vcpu_irqs(struct its_vm *vm) { int vpe_base_irq, i; + if (!gic_domain) + return -EINVAL; + vm->fwnode = irq_domain_alloc_named_id_fwnode("GICv4-vpe", task_pid_nr(current)); if (!vm->fwnode) -- 2.54.0.669.g59709faab0-goog ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] irqchip/gic-v4: Harden against bogus command line 2026-05-21 13:05 [PATCH] irqchip/gic-v4: Harden against bogus command line Mostafa Saleh @ 2026-05-23 9:53 ` Marc Zyngier 2026-05-26 7:50 ` Mostafa Saleh 0 siblings, 1 reply; 4+ messages in thread From: Marc Zyngier @ 2026-05-23 9:53 UTC (permalink / raw) To: Mostafa Saleh; +Cc: linux-arm-kernel, linux-kernel, tglx On Thu, 21 May 2026 14:05:03 +0100, Mostafa Saleh <smostafa@google.com> wrote: > > When accidentally setting “kvm-arm.vgic_v4_enable=1” on the wrong > setup that has no MSI controller device tree node (it exists but > not used) and GICv4, it caused a panic as “gic_domain” is NULL and > the kernel attempted to access its ops. When you say "that has no MSI controller device tree node", does it mean that the ITS has not been probed at all? > > Originally, I hit this on an older kernel, but was able to reproduce > it on upstream with Qemu by hacking this unreasonable setup. > > [ 33.145536] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000028 > [ 33.145658] Mem abort info: > [ 33.145751] ESR = 0x0000000096000006 > ... > [ 33.154057] CPU: 1 UID: 0 PID: 295 Comm: lkvm-static Not tainted 7.1.0-rc4-ge3f15ad3970e #5 PREEMPT > [ 33.156922] Hardware name: linux,dummy-virt (DT) > [ 33.158780] pstate: 81402005 (Nzcv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) > [ 33.160340] pc : __irq_domain_instantiate+0x1d4/0x578 > [ 33.162602] lr : __irq_domain_instantiate+0x1cc/0x578 > > Add a hardening check to avoid the NULL access, and fail the VM > creation in that case. > > Signed-off-by: Mostafa Saleh <smostafa@google.com> > --- > drivers/irqchip/irq-gic-v4.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/irqchip/irq-gic-v4.c b/drivers/irqchip/irq-gic-v4.c > index 8455b4a5fbb0..7e39f7eae85f 100644 > --- a/drivers/irqchip/irq-gic-v4.c > +++ b/drivers/irqchip/irq-gic-v4.c > @@ -159,6 +159,9 @@ int its_alloc_vcpu_irqs(struct its_vm *vm) > { > int vpe_base_irq, i; > > + if (!gic_domain) > + return -EINVAL; > + > vm->fwnode = irq_domain_alloc_named_id_fwnode("GICv4-vpe", > task_pid_nr(current)); > if (!vm->fwnode) I think this check is a good few levels too late. If you want to fix this, I'd rather make sure that kvm_vgic_global_state.has_gicv4 is reliable and covers this case. Which means making sure that gic_kvm_info::has_v4 is itself reliable. If my above understanding is correct, I'd expect the following (untested) hack to help. Thanks, M. diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c index 291d7668cc8da..e6b9fee1b6786 100644 --- a/drivers/irqchip/irq-gic-v3-its.c +++ b/drivers/irqchip/irq-gic-v3-its.c @@ -5838,6 +5838,7 @@ int __init its_init(struct fwnode_handle *handle, struct rdists *rdists, if (list_empty(&its_nodes)) { pr_warn("ITS: No ITS available, not enabling LPIs\n"); + rdists->has_vlpis = false; return -ENXIO; } -- Without deviation from the norm, progress is not possible. ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] irqchip/gic-v4: Harden against bogus command line 2026-05-23 9:53 ` Marc Zyngier @ 2026-05-26 7:50 ` Mostafa Saleh 2026-05-26 9:45 ` Marc Zyngier 0 siblings, 1 reply; 4+ messages in thread From: Mostafa Saleh @ 2026-05-26 7:50 UTC (permalink / raw) To: Marc Zyngier; +Cc: linux-arm-kernel, linux-kernel, tglx On Sat, May 23, 2026 at 10:53:23AM +0100, Marc Zyngier wrote: > On Thu, 21 May 2026 14:05:03 +0100, > Mostafa Saleh <smostafa@google.com> wrote: > > > > When accidentally setting “kvm-arm.vgic_v4_enable=1” on the wrong > > setup that has no MSI controller device tree node (it exists but > > not used) and GICv4, it caused a panic as “gic_domain” is NULL and > > the kernel attempted to access its ops. > > When you say "that has no MSI controller device tree node", does it > mean that the ITS has not been probed at all? Yes. > > > > > Originally, I hit this on an older kernel, but was able to reproduce > > it on upstream with Qemu by hacking this unreasonable setup. > > > > [ 33.145536] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000028 > > [ 33.145658] Mem abort info: > > [ 33.145751] ESR = 0x0000000096000006 > > ... > > [ 33.154057] CPU: 1 UID: 0 PID: 295 Comm: lkvm-static Not tainted 7.1.0-rc4-ge3f15ad3970e #5 PREEMPT > > [ 33.156922] Hardware name: linux,dummy-virt (DT) > > [ 33.158780] pstate: 81402005 (Nzcv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) > > [ 33.160340] pc : __irq_domain_instantiate+0x1d4/0x578 > > [ 33.162602] lr : __irq_domain_instantiate+0x1cc/0x578 > > > > Add a hardening check to avoid the NULL access, and fail the VM > > creation in that case. > > > > Signed-off-by: Mostafa Saleh <smostafa@google.com> > > --- > > drivers/irqchip/irq-gic-v4.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/irqchip/irq-gic-v4.c b/drivers/irqchip/irq-gic-v4.c > > index 8455b4a5fbb0..7e39f7eae85f 100644 > > --- a/drivers/irqchip/irq-gic-v4.c > > +++ b/drivers/irqchip/irq-gic-v4.c > > @@ -159,6 +159,9 @@ int its_alloc_vcpu_irqs(struct its_vm *vm) > > { > > int vpe_base_irq, i; > > > > + if (!gic_domain) > > + return -EINVAL; > > + > > vm->fwnode = irq_domain_alloc_named_id_fwnode("GICv4-vpe", > > task_pid_nr(current)); > > if (!vm->fwnode) > > I think this check is a good few levels too late. If you want to fix > this, I'd rather make sure that kvm_vgic_global_state.has_gicv4 is > reliable and covers this case. Which means making sure that > gic_kvm_info::has_v4 is itself reliable. > > If my above understanding is correct, I'd expect the following > (untested) hack to help. Thanks! That also fixes the crash, the VM will launch with a vGIC with no ITS in that case. Thanks, Mostafa > > Thanks, > > M. > > diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c > index 291d7668cc8da..e6b9fee1b6786 100644 > --- a/drivers/irqchip/irq-gic-v3-its.c > +++ b/drivers/irqchip/irq-gic-v3-its.c > @@ -5838,6 +5838,7 @@ int __init its_init(struct fwnode_handle *handle, struct rdists *rdists, > > if (list_empty(&its_nodes)) { > pr_warn("ITS: No ITS available, not enabling LPIs\n"); > + rdists->has_vlpis = false; > return -ENXIO; > } > > > -- > Without deviation from the norm, progress is not possible. ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] irqchip/gic-v4: Harden against bogus command line 2026-05-26 7:50 ` Mostafa Saleh @ 2026-05-26 9:45 ` Marc Zyngier 0 siblings, 0 replies; 4+ messages in thread From: Marc Zyngier @ 2026-05-26 9:45 UTC (permalink / raw) To: Mostafa Saleh; +Cc: linux-arm-kernel, linux-kernel, tglx On Tue, 26 May 2026 08:50:13 +0100, Mostafa Saleh <smostafa@google.com> wrote: > > On Sat, May 23, 2026 at 10:53:23AM +0100, Marc Zyngier wrote: > > On Thu, 21 May 2026 14:05:03 +0100, > > Mostafa Saleh <smostafa@google.com> wrote: > > > > > > When accidentally setting “kvm-arm.vgic_v4_enable=1” on the wrong > > > setup that has no MSI controller device tree node (it exists but > > > not used) and GICv4, it caused a panic as “gic_domain” is NULL and > > > the kernel attempted to access its ops. > > > > When you say "that has no MSI controller device tree node", does it > > mean that the ITS has not been probed at all? > > Yes. > > > > > > > > > Originally, I hit this on an older kernel, but was able to reproduce > > > it on upstream with Qemu by hacking this unreasonable setup. > > > > > > [ 33.145536] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000028 > > > [ 33.145658] Mem abort info: > > > [ 33.145751] ESR = 0x0000000096000006 > > > ... > > > [ 33.154057] CPU: 1 UID: 0 PID: 295 Comm: lkvm-static Not tainted 7.1.0-rc4-ge3f15ad3970e #5 PREEMPT > > > [ 33.156922] Hardware name: linux,dummy-virt (DT) > > > [ 33.158780] pstate: 81402005 (Nzcv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) > > > [ 33.160340] pc : __irq_domain_instantiate+0x1d4/0x578 > > > [ 33.162602] lr : __irq_domain_instantiate+0x1cc/0x578 > > > > > > Add a hardening check to avoid the NULL access, and fail the VM > > > creation in that case. > > > > > > Signed-off-by: Mostafa Saleh <smostafa@google.com> > > > --- > > > drivers/irqchip/irq-gic-v4.c | 3 +++ > > > 1 file changed, 3 insertions(+) > > > > > > diff --git a/drivers/irqchip/irq-gic-v4.c b/drivers/irqchip/irq-gic-v4.c > > > index 8455b4a5fbb0..7e39f7eae85f 100644 > > > --- a/drivers/irqchip/irq-gic-v4.c > > > +++ b/drivers/irqchip/irq-gic-v4.c > > > @@ -159,6 +159,9 @@ int its_alloc_vcpu_irqs(struct its_vm *vm) > > > { > > > int vpe_base_irq, i; > > > > > > + if (!gic_domain) > > > + return -EINVAL; > > > + > > > vm->fwnode = irq_domain_alloc_named_id_fwnode("GICv4-vpe", > > > task_pid_nr(current)); > > > if (!vm->fwnode) > > > > I think this check is a good few levels too late. If you want to fix > > this, I'd rather make sure that kvm_vgic_global_state.has_gicv4 is > > reliable and covers this case. Which means making sure that > > gic_kvm_info::has_v4 is itself reliable. > > > > If my above understanding is correct, I'd expect the following > > (untested) hack to help. > > Thanks! That also fixes the crash, the VM will launch with a vGIC with > no ITS in that case. You should still be able to have a virtual ITS, just no direct injection of any sort. If you're happy with that, please respin a patch with this hack. Thanks, M. -- Without deviation from the norm, progress is not possible. ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2026-05-26 9:45 UTC | newest] Thread overview: 4+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2026-05-21 13:05 [PATCH] irqchip/gic-v4: Harden against bogus command line Mostafa Saleh 2026-05-23 9:53 ` Marc Zyngier 2026-05-26 7:50 ` Mostafa Saleh 2026-05-26 9:45 ` Marc Zyngier
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