Re: [PATCH 1/1] iommu/vt-d: Remove unnecessary WARN_ON_ONCE()

Joerg Roedel
2020-01-17T10:00:09Z

On Thu, Jan 16, 2020 at 09:52:36AM +0800, Lu Baolu wrote:
> 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@posteo.de>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>

Does this need a Fixes and/or stable tag?

Regards,

Joerg