From: Stanislav Kinsburskii Date: Thu, 7 May 2026 15:43:15 +0000 (+0000) Subject: mshv: Fix race in mshv_irqfd_deassign X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0762262ac3e70f65b3bb843fe892f8bac1562d08;p=thirdparty%2Flinux.git mshv: Fix race in mshv_irqfd_deassign mshv_irqfd_deactivate() and the hlist traversal of pt_irqfds_list require pt->pt_irqfds_lock to be held, but mshv_irqfd_deassign() omits it. This races with the EPOLLHUP path in mshv_irqfd_wakeup(), which does take the lock before calling mshv_irqfd_deactivate(). Additionally, mshv_irqfd_deactivate() uses hlist_del() which poisons the node pointers rather than resetting them. Since mshv_irqfd_is_active() relies on hlist_unhashed() (checks pprev == NULL), a poisoned node still appears active. If a concurrent path calls mshv_irqfd_deactivate() again on the same irqfd, the guard fails to prevent a double hlist_del() on poisoned pointers. Fix both issues: - Add the missing spin_lock_irq/spin_unlock_irq around the list traversal in mshv_irqfd_deassign(), matching mshv_irqfd_release(). - Use hlist_del_init() instead of hlist_del() so the node is properly marked as unhashed after removal, making the is_active guard reliable. Fixes: 621191d709b14 ("Drivers: hv: Introduce mshv_root module to expose /dev/mshv to VMMs") Signed-off-by: Stanislav Kinsburskii Reviewed-by: Anirudh Rayabharam (Microsoft) Signed-off-by: Wei Liu --- diff --git a/drivers/hv/mshv_eventfd.c b/drivers/hv/mshv_eventfd.c index 90959f639dc3..5995a62aff8d 100644 --- a/drivers/hv/mshv_eventfd.c +++ b/drivers/hv/mshv_eventfd.c @@ -284,7 +284,7 @@ static void mshv_irqfd_deactivate(struct mshv_irqfd *irqfd) if (!mshv_irqfd_is_active(irqfd)) return; - hlist_del(&irqfd->irqfd_hnode); + hlist_del_init(&irqfd->irqfd_hnode); queue_work(irqfd_cleanup_wq, &irqfd->irqfd_shutdown); } @@ -541,13 +541,14 @@ static int mshv_irqfd_deassign(struct mshv_partition *pt, if (IS_ERR(eventfd)) return PTR_ERR(eventfd); + spin_lock_irq(&pt->pt_irqfds_lock); hlist_for_each_entry_safe(irqfd, n, &pt->pt_irqfds_list, irqfd_hnode) { if (irqfd->irqfd_eventfd_ctx == eventfd && irqfd->irqfd_irqnum == args->gsi) - mshv_irqfd_deactivate(irqfd); } + spin_unlock_irq(&pt->pt_irqfds_lock); eventfd_ctx_put(eventfd);