On Tue, Mar 17, 2026 at 09:56:07PM +0000, Michael Kelley wrote: > From: Stanislav Kinsburskii <[email protected]> Sent: Tuesday, > March 17, 2026 8:05 AM > > > > The current error handling has two issues: > > > > First, pin_user_pages_fast() can return a short pin count (less than > > requested but greater than zero) when it cannot pin all requested pages. > > This is treated as success, leading to partially pinned regions being > > used, which causes memory corruption. > > > > Second, when an error occurs mid-loop, already pinned pages from the > > current batch are not released before calling mshv_region_evict_pages(), > > causing a page reference leak. > > There's now an online LLM-based tool that is automatically reviewing > kernel patches. For this patch, the results are here: > > https://sashiko.dev/#/patchset/177375989324.25621.6532741522672582851.stgit%40skinsburskii-cloud-desktop.internal.cloudapp.net > > It has flagged the commit message as incorrectly referencing the > function mshv_region_evict_pages(), which doesn't exist. > > FWIW, the announcement about sashiko.dev is here: > > https://lore.kernel.org/lkml/[email protected]/ > > Other than the commit message reference, this looks good to me. > > Reviewed-by: Michael Kelley <[email protected]>
The second point is written as if the code here should release the already pinned pages before calling mshv_region_invalidate_pages(), but the code actually relies on mshv_mem_region_invalidate_pages() to release the pages. The change here fixes the accounting. Second, when an error occurs mid-loop, already pinned pages from the current batch are not accounted for before calling mshv_region_invalidate_pages(), causing a page reference leak. And queued up the patch to hyperv-fixes. Wei > > > > > Fix by treating short pins as errors and explicitly unpinning the > > partial batch before cleanup. > > > > Signed-off-by: Stanislav Kinsburskii <[email protected]> > > --- > > drivers/hv/mshv_regions.c | 6 ++++-- > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/hv/mshv_regions.c b/drivers/hv/mshv_regions.c > > index c28aac0726de..fdffd4f002f6 100644 > > --- a/drivers/hv/mshv_regions.c > > +++ b/drivers/hv/mshv_regions.c > > @@ -314,15 +314,17 @@ int mshv_region_pin(struct mshv_mem_region *region) > > ret = pin_user_pages_fast(userspace_addr, nr_pages, > > FOLL_WRITE | FOLL_LONGTERM, > > pages); > > - if (ret < 0) > > + if (ret != nr_pages) > > goto release_pages; > > } > > > > return 0; > > > > release_pages: > > + if (ret > 0) > > + done_count += ret; > > mshv_region_invalidate_pages(region, 0, done_count); > > - return ret; > > + return ret < 0 ? ret : -ENOMEM; > > } > > > > static int mshv_region_chunk_unmap(struct mshv_mem_region *region, > > > > >
