Re: [PATCH] block/nvme: Fix VFIO_MAP_DMA failed: No space left on device

[Michal Prívozník]

On 6/14/21 6:03 PM, Philippe Mathieu-Daudé wrote:
> On 6/11/21 1:46 PM, Philippe Mathieu-Daudé wrote:
>> When the NVMe block driver was introduced (see commit bdd6a90a9e5,
>> January 2018), Linux VFIO_IOMMU_MAP_DMA ioctl was only returning
>> -ENOMEM in case of error. The driver was correctly handling the
>> error path to recycle its volatile IOVA mappings.
>>
>> To fix CVE-2019-3882, Linux commit 492855939bdb ("vfio/type1: Limit
>> DMA mappings per container", April 2019) added the -ENOSPC error to
>> signal the user exhausted the DMA mappings available for a container.
> 
> Hmm this commit has been added before v5.1-rc4.
> 
> So while this fixes the behavior of v5.1-rc4+ kernels,
> older kernels using this fix will have the same problem...
> 
> Should I check uname(2)'s utsname.release[]? Is it reliable?

Not at all. What if somebody runs kernel with that commit backported? I
would leave this up to distro maintainers to figure out. They know what
kernel patches are backported and thus what qemu patches should be
backported too. I'm wondering if there's a way we can help them by
letting know (other than mentioning the kernel commit).

Michal