From 14ae3003e73e777c9b36385a7c86f754b50a1821 Mon Sep 17 00:00:00 2001 From: Michael Kelley Date: Mon, 21 Apr 2025 09:31:34 -0700 Subject: [PATCH] Drivers: hv: Fix bad ref to hv_synic_eventring_tail when CPU goes offline When a CPU goes offline, hv_common_cpu_die() frees the hv_synic_eventring_tail memory for the CPU. But in a normal VM (i.e., not running in the root partition) the per-CPU memory has not been allocated, resulting in a bad memory reference and oops when computing the argument to kfree(). Fix this by freeing the memory only when running in the root partition. Fixes: 04df7ac39943 ("Drivers: hv: Introduce per-cpu event ring tail") Signed-off-by: Michael Kelley Reviewed-by: Nuno Das Neves Link: https://lore.kernel.org/r/20250421163134.2024-1-mhklinux@outlook.com Signed-off-by: Wei Liu Message-ID: <20250421163134.2024-1-mhklinux@outlook.com> --- drivers/hv/hv_common.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c index a7d7494feaca..59792e00cecf 100644 --- a/drivers/hv/hv_common.c +++ b/drivers/hv/hv_common.c @@ -566,9 +566,11 @@ int hv_common_cpu_die(unsigned int cpu) * originally allocated memory is reused in hv_common_cpu_init(). */ - synic_eventring_tail = this_cpu_ptr(hv_synic_eventring_tail); - kfree(*synic_eventring_tail); - *synic_eventring_tail = NULL; + if (hv_root_partition()) { + synic_eventring_tail = this_cpu_ptr(hv_synic_eventring_tail); + kfree(*synic_eventring_tail); + *synic_eventring_tail = NULL; + } return 0; }