On 2020-03-03 17:23, Robin Murphy wrote:
On 03/03/2020 11:51 am, Marc Zyngier wrote:
The way cookie_init_hw_msi_region() allocates the iommu_dma_msi_page structures doesn't match the way iommu_put_dma_cookie() frees them.
The former performs a single allocation of all the required structures, while the latter tries to free them one at a time. It doesn't quite work for the main use case (the GICv3 ITS where the range is 64kB) when the base ganule size is 4kB.
This leads to a nice slab corruption on teardown, which is easily observable by simply creating a VF on a SRIOV-capable device, and tearing it down immediately (no need to even make use of it).
Fix it by allocating iommu_dma_msi_page structures one at a time.
Bleh, you know you're supposed to be using 64K pages on those things, right? :P
lalalala... ;-)
[...]
if (!msi_page) {ret = -ENOMEM;I think we can just return here and skip the cleanup below - by the time we get here the cookie itself has already been allocated and initialised, so even if iommu_dma_init_domain() fails someone else has already accepted the responsibility of calling iommu_put_dma_cookie() at some point later, which will clean up properly.
Ah, that's a very good point. I'll refresh the patch with a simplified error handling.
Thanks,
M.