From: Greg Edwards Date: Wed, 23 Jul 2014 16:13:26 +0000 (-0600) Subject: iommu/vt-d: Fix race setting IRQ CPU affinity while freeing IRQ X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=af437469d14e91e8b4273606cac4c08f05bf056e;p=linux-beck.git iommu/vt-d: Fix race setting IRQ CPU affinity while freeing IRQ A user process setting the CPU affinity of an IRQ for a KVM direct-assigned device via /proc/irq//smp_affinity can race with the IRQ being released by QEMU, resulting in a NULL iommu pointer dereference in get_irte(), causing this crash: BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 IP: [] intel_ioapic_set_affinity+0x82/0x1b0 PGD 99172e067 PUD 1026979067 PMD 0 Oops: 0000 [#1] SMP Modules linked in: CPU: 1 PID: 3354 Comm: affin Not tainted 3.16.0-rc7-00007-g31dab71 #1 Hardware name: Supermicro SYS-F617R2-RT+/X9DRFR, BIOS 3.0a 01/29/2014 task: ffff881025b0e720 ti: ffff88099173c000 task.ti: ffff88099173c000 RIP: 0010:[] [] intel_ioapic_set_affinity+0x82/0x1b0 RSP: 0018:ffff88099173fdb0 EFLAGS: 00010046 RAX: 0000000000000082 RBX: ffff880a36294600 RCX: 0000000000000082 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff8266af00 RBP: ffff88099173fdf8 R08: 0000000000000000 R09: ffff88103ec00490 R10: 0000000000000000 R11: 0000000000000000 R12: ffff88099173fe90 R13: 000000000000005f R14: ffff880faa38fe80 R15: ffff880faa38fe80 FS: 00007f7161f05740(0000) GS:ffff88107fc40000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000090 CR3: 000000099140d000 CR4: 00000000001427e0 Stack: ffffffff81c44740 ffff88099173fdc8 ffffffff00000000 00000000c991fd3b ffff880a36294600 ffff88099173fe90 ffff88099173fe90 0000000000000000 0000000000000286 ffff88099173fe08 ffffffff8190aac5 ffff88099173fe28 Call Trace: [] set_remapped_irq_affinity+0x25/0x40 [] irq_do_set_affinity+0x1c/0x50 [] irq_set_affinity_locked+0x98/0xd0 [] __irq_set_affinity+0x46/0x70 [] write_irq_affinity.isra.6+0xdc/0x100 [] irq_affinity_list_proc_write+0x1c/0x20 [] proc_reg_write+0x3d/0x80 [] vfs_write+0xb7/0x1f0 [] ? putname+0x29/0x40 [] SyS_write+0x55/0xd0 [] system_call_fastpath+0x16/0x1b Code: ff 48 85 d2 74 68 4c 8b 7a 30 4d 85 ff 74 5f 48 c7 c7 00 af 66 82 e8 9e 1b 1d 00 49 8b 57 20 41 0f b7 77 28 48 c7 c7 00 af 66 82 <48> 8b 8a 90 00 00 00 41 0f b7 57 2a 01 f2 48 89 c6 48 63 d2 48 RIP [] intel_ioapic_set_affinity+0x82/0x1b0 RSP CR2: 0000000000000090 Signed-off-by: Greg Edwards Signed-off-by: Joerg Roedel --- diff --git a/drivers/iommu/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c index 757e0b0d19ff..0df41f6264f5 100644 --- a/drivers/iommu/intel_irq_remapping.c +++ b/drivers/iommu/intel_irq_remapping.c @@ -70,6 +70,11 @@ static int get_irte(int irq, struct irte *entry) raw_spin_lock_irqsave(&irq_2_ir_lock, flags); + if (unlikely(!irq_iommu->iommu)) { + raw_spin_unlock_irqrestore(&irq_2_ir_lock, flags); + return -1; + } + index = irq_iommu->irte_index + irq_iommu->sub_handle; *entry = *(irq_iommu->iommu->ir_table->base + index);