From 874194a8de75fc2f4d1fb70c670b289b7e48f93e Mon Sep 17 00:00:00 2001 From: Hardik Garg Date: Fri, 11 Sep 2026 17:51:46 +0000 Subject: [PATCH] mshv_vtl: Check per-CPU register page before mmap Register-page setup is optional for each CPU. If allocation or registration fails, mshv_vtl_configure_reg_page() warns and leaves that CPU's reg_page NULL, but initial context setup continues successfully. Meanwhile, successful setup on another CPU sets the global mshv_has_reg_page flag. mshv_vtl_fault() checks this global flag before selecting the requested CPU's register page. With mixed setup results across online CPUs, the check passes even for a CPU with no register page, reaching get_page(NULL) when userspace faults in that mapping. Check the selected per-CPU register page before taking its reference and return VM_FAULT_SIGBUS if it is absent. Fixes: 7bfe3b8ea6e3 ("Drivers: hv: Introduce mshv_vtl driver") Cc: stable@vger.kernel.org Signed-off-by: Hardik Garg Reviewed-by: Naman Jain Signed-off-by: Wei Liu --- drivers/hv/mshv_vtl_main.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/hv/mshv_vtl_main.c b/drivers/hv/mshv_vtl_main.c index 6e3c11c68171..d8225242c73f 100644 --- a/drivers/hv/mshv_vtl_main.c +++ b/drivers/hv/mshv_vtl_main.c @@ -819,6 +819,9 @@ static vm_fault_t mshv_vtl_fault(struct vm_fault *vmf) return VM_FAULT_NOPAGE; } + if (!page) + return VM_FAULT_SIGBUS; + get_page(page); vmf->page = page;