linux-kernel - [PATCH 1/1] iommu/vt-d: Remove unnecessary WARN_ON

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Message-Id: <20200116015236.4458-1-baolu.lu@linux.intel.com>
Date:   Thu, 16 Jan 2020 09:52:36 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     ashok.raj@...el.com, jacob.jun.pan@...el.com, kevin.tian@...el.com,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Lu Baolu <baolu.lu@...ux.intel.com>
Subject: [PATCH 1/1] iommu/vt-d: Remove unnecessary WARN_ON_ONCE()

Address field in device TLB invalidation descriptor is qualified
by the S field. If S field is zero, a single page at page address
specified by address [63:12] is requested to be invalidated. If S
field is set, the least significant bit in the address field with
value 0b (say bit N) indicates the invalidation address range. The
spec doesn't require the address [N - 1, 0] to be cleared, hence
remove the unnecessary WARN_ON_ONCE().

Otherwise, the caller might set "mask = MAX_AGAW_PFN_WIDTH" in order
to invalidating all the cached mappings on an endpoint, and below
overflow error will be triggered.

[...]
UBSAN: Undefined behaviour in drivers/iommu/dmar.c:1354:3
shift exponent 64 is too large for 64-bit type 'long long unsigned int'
[...]

Reported-and-tested-by: Frank <fgndev@...teo.de>
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
---
 drivers/iommu/dmar.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index 613b7153905d..071bb42bbbc5 100644
--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -1354,7 +1354,6 @@ void qi_flush_dev_iotlb(struct intel_iommu *iommu, u16 sid, u16 pfsid,
 	struct qi_desc desc;

 	if (mask) {
-		WARN_ON_ONCE(addr & ((1ULL << (VTD_PAGE_SHIFT + mask)) - 1));
 		addr |= (1ULL << (VTD_PAGE_SHIFT + mask - 1)) - 1;
 		desc.qw1 = QI_DEV_IOTLB_ADDR(addr) | QI_DEV_IOTLB_SIZE;
 	} else
-- 
2.17.1