Re: [PATCH v2 0/2] mshv_vtl: fix poll waitqueue handling

[Wei Liu <wei.liu@kernel.org>]

On Mon, Oct 19, 2026 at 02:37:39PM +0530, Naman Jain wrote:
> 
> 
> On 10/19/2026 2:13 PM, Daehyeon Ko wrote:
> > MSHV_SET_POLL_FILE retains one embedded wait entry per CPU after vfs_poll()
> > returns. Two independent bugs affect that state.
> > 
> > First, a provider such as signalfd may retire a non-file-owned waitqueue
> > with POLLFREE. The MSHV callback leaves its entry linked and retains the
> > queue pointer, allowing a later replacement to access freed provider
> > memory. Patch 1 detaches on POLLFREE and introduces an RCU-safe removal
> > helper.
> > 
> > Second, a poll callback may register more than one waitqueue. MSHV inserts
> > the same embedded list node into each queue, corrupting the first list.
> > Patch 2 rejects a second distinct queue and uses the common helper to
> > unwind the first registration.
> > 
> > The roots, triggers, effects, and runtime oracles remain independent.
> > Source-equivalent KASAN/LOCKDEP tests reproduced both bugs and validated
> > the fixes. The local system is not a Hyper-V VTL2 environment, so the
> > series has not been exercised through the real MSHV ioctl. OpenVMM does
> > not exercise these paths in its current use of the interface.
> > 
> > An LLM assisted the source audits, fix development, and validation. Each
> > patch notes that assistance in its changelog.
> > 
> > Changes in v2:
> > - combine the two previously standalone fixes into one series;
> > - rebase onto current Torvalds master;
> > - introduce the removal helper in patch 1 and reuse it in patch 2;
> > - replace the obsolete Assisted-by trailer with changelog prose.
> > 
> > Previous standalone submissions:
> > - POLLFREE v1: <20261017141527.623376-1-4ncienth@gmail.com>
> > - multi-waitqueue v2, now withdrawn:
> >    <20261019070438.3732624-1-4ncienth@gmail.com>
> > 
> > Daehyeon Ko (2):
> >    mshv_vtl: detach poll waiter on POLLFREE
> >    mshv_vtl: reject poll files with multiple waitqueues
> > 
> >   drivers/hv/mshv_vtl_main.c | 51 ++++++++++++++++++++++++++++++++++----
> >   1 file changed, 46 insertions(+), 5 deletions(-)
> > 
> > 
> > base-commit: c03c1a14507dfaf8b856c2608f9ac216021fc222
> 
> I would suggest you to generally wait for a couple more days to collect
> other reviewers feedback as well, in case someone is reviewing your changes.
> You can then address them together in the next version.
> 
> For the series,
> Reviewed-by: Naman Jain <namjain@linux.microsoft.com>

Applied.

Wei