The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 7f11a2cc10a4ae3a70e2c73361f4a9a33503539b Mon Sep 17 00:00:00 2001

From: Tianyu Lan Tianyu.Lan@microsoft.com Date: Mon, 6 Apr 2020 08:53:27 -0700 Subject: [PATCH] x86/Hyper-V: Free hv_panic_page when fail to register kmsg dump

If kmsg_dump_register() fails, hv_panic_page will not be used anywhere. So free and reset it.

Fixes: 81b18bce48af ("Drivers: HV: Send one page worth of kmsg dump over Hyper-V during panic") Reviewed-by: Michael Kelley mikelley@microsoft.com Signed-off-by: Tianyu Lan Tianyu.Lan@microsoft.com Link: https://lore.kernel.org/r/20200406155331.2105-3-Tianyu.Lan@microsoft.com Signed-off-by: Wei Liu wei.liu@kernel.org

diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 6478240d11ab..00a511f15926 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -1385,9 +1385,13 @@ static int vmbus_bus_init(void) hv_panic_page = (void *)hv_alloc_hyperv_zeroed_page(); if (hv_panic_page) { ret = kmsg_dump_register(&hv_kmsg_dumper); - if (ret) + if (ret) { pr_err("Hyper-V: kmsg dump register " "error 0x%x\n", ret); + hv_free_hyperv_page( + (unsigned long)hv_panic_page); + hv_panic_page = NULL; + } } else pr_err("Hyper-V: panic message page memory " "allocation failed"); @@ -1416,7 +1420,6 @@ static int vmbus_bus_init(void) hv_remove_vmbus_irq();

bus_unregister(&hv_bus); - hv_free_hyperv_page((unsigned long)hv_panic_page); unregister_sysctl_table(hv_ctl_table_hdr); hv_ctl_table_hdr = NULL; return ret;