On Wed, Mar 18, 2026 at 04:20:03PM +0000, Wei Liu wrote: > On Wed, Mar 18, 2026 at 02:38:49PM +0000, Michael Kelley wrote: > > From: Wei Liu <[email protected]> Sent: Tuesday, March 17, 2026 11:20 PM > > > > > > 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. > > > > One other thing I noticed: The "Subject" of the patch is wrong. It > > mentions mshv_region_populate_pages(), but the function being > > modified is actually mshv_region_pin(). > > Good catch. I have updated the subject line and pushed to hyperv-fixes. >
Thank you Michael and Wei. Thanks, Stanislav > Wei > > > > > Michael > > > > > > > > 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, > > > > > > > > > > > > > > > >
