linux-kernel - Re: [RESEND][PATCH] iommu/vt-d: fix shift-out-of-bounds in bug checking

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Date:   Thu, 3 May 2018 07:56:27 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     changbin.du@...el.com, jroedel@...e.de,
        iommu@...ts.linux-foundation.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [RESEND][PATCH] iommu/vt-d: fix shift-out-of-bounds in bug
 checking

Hi,

On 04/28/2018 02:39 PM, changbin.du@...el.com wrote:
> From: Changbin Du <changbin.du@...el.com>
>
> It allows to flush more than 4GB of device TLBs. So the mask should be
> 64bit wide. UBSAN captured this fault as below.
>
> [    3.760024] ================================================================================
> [    3.768440] UBSAN: Undefined behaviour in drivers/iommu/dmar.c:1348:3
> [    3.774864] shift exponent 64 is too large for 32-bit type 'int'
> [    3.780853] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G     U            4.17.0-rc1+ #89
> [    3.788661] Hardware name: Dell Inc. OptiPlex 7040/0Y7WYT, BIOS 1.2.8 01/26/2016
> [    3.796034] Call Trace:
> [    3.798472]  <IRQ>
> [    3.800479]  dump_stack+0x90/0xfb
> [    3.803787]  ubsan_epilogue+0x9/0x40
> [    3.807353]  __ubsan_handle_shift_out_of_bounds+0x10e/0x170
> [    3.812916]  ? qi_flush_dev_iotlb+0x124/0x180
> [    3.817261]  qi_flush_dev_iotlb+0x124/0x180
> [    3.821437]  iommu_flush_dev_iotlb+0x94/0xf0
> [    3.825698]  iommu_flush_iova+0x10b/0x1c0
> [    3.829699]  ? fq_ring_free+0x1d0/0x1d0
> [    3.833527]  iova_domain_flush+0x25/0x40
> [    3.837448]  fq_flush_timeout+0x55/0x160
> [    3.841368]  ? fq_ring_free+0x1d0/0x1d0
> [    3.845200]  ? fq_ring_free+0x1d0/0x1d0
> [    3.849034]  call_timer_fn+0xbe/0x310
> [    3.852696]  ? fq_ring_free+0x1d0/0x1d0
> [    3.856530]  run_timer_softirq+0x223/0x6e0
> [    3.860625]  ? sched_clock+0x5/0x10
> [    3.864108]  ? sched_clock+0x5/0x10
> [    3.867594]  __do_softirq+0x1b5/0x6f5
> [    3.871250]  irq_exit+0xd4/0x130
> [    3.874470]  smp_apic_timer_interrupt+0xb8/0x2f0
> [    3.879075]  apic_timer_interrupt+0xf/0x20
> [    3.883159]  </IRQ>
> [    3.885255] RIP: 0010:poll_idle+0x60/0xe7
> [    3.889252] RSP: 0018:ffffb1b201943e30 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
> [    3.896802] RAX: 0000000080200000 RBX: 000000000000008e RCX: 000000000000001f
> [    3.903918] RDX: 0000000000000000 RSI: 000000002819aa06 RDI: 0000000000000000
> [    3.911031] RBP: ffff9e93c6b33280 R08: 00000010f717d567 R09: 000000000010d205
> [    3.918146] R10: ffffb1b201943df8 R11: 0000000000000001 R12: 00000000e01b169d
> [    3.925260] R13: 0000000000000000 R14: ffffffffb12aa400 R15: 0000000000000000
> [    3.932382]  cpuidle_enter_state+0xb4/0x470
> [    3.936558]  do_idle+0x222/0x310
> [    3.939779]  cpu_startup_entry+0x78/0x90
> [    3.943693]  start_secondary+0x205/0x2e0
> [    3.947607]  secondary_startup_64+0xa5/0xb0
> [    3.951783] ================================================================================

This looks good to me.

Best regards,
Lu Baolu

> Signed-off-by: Changbin Du <changbin.du@...el.com>
> ---
>  drivers/iommu/dmar.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
> index accf5838..e4ae600 100644
> --- a/drivers/iommu/dmar.c
> +++ b/drivers/iommu/dmar.c
> @@ -1345,7 +1345,7 @@ void qi_flush_dev_iotlb(struct intel_iommu *iommu, u16 sid, u16 qdep,
>  	struct qi_desc desc;
>  
>  	if (mask) {
> -		BUG_ON(addr & ((1 << (VTD_PAGE_SHIFT + mask)) - 1));
> +		BUG_ON(addr & ((1ULL << (VTD_PAGE_SHIFT + mask)) - 1));
>  		addr |= (1ULL << (VTD_PAGE_SHIFT + mask - 1)) - 1;
>  		desc.high = QI_DEV_IOTLB_ADDR(addr) | QI_DEV_IOTLB_SIZE;
>  	} else