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Patch "Drivers: hv: avoid vfree() on crash" has been added to the 4.4-stable tree

PATCH [email protected] 1 participant 1 message Mar 22, 2017

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Stable branch Hyper-V/Azure core and drivers
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This is a note to let you know that I've just added the patch titled

Drivers: hv: avoid vfree() on crash

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drivers-hv-avoid-vfree-on-crash.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From a9f61ca793becabdefab03b77568d6c6f8c1bc79 Mon Sep 17 00:00:00 2001

From: Vitaly Kuznetsov <[email protected]>
Date: Fri, 3 Jun 2016 17:09:22 -0700
Subject: Drivers: hv: avoid vfree() on crash

From: Vitaly Kuznetsov <[email protected]>

commit a9f61ca793becabdefab03b77568d6c6f8c1bc79 upstream.

When we crash from NMI context (e.g. after NMI injection from host when 'sysctl -w kernel.unknown_nmi_panic=1' is set) we hit

kernel BUG at mm/vmalloc.c:1530!

as vfree() is denied. While the issue could be solved with in_nmi() check instead I opted for skipping vfree on all sorts of crashes to reduce the amount of work which can cause consequent crashes. We don't really need to free anything on crash.

Signed-off-by Vitaly Kuznetsov <[email protected]>
Signed-off-by K. Y. Srinivasan <[email protected]>
Cc Sumit Semwal <[email protected]>
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/hv/hv.c           |    8 +++++---
 drivers/hv/hyperv_vmbus.h |    2 +-
 drivers/hv/vmbus_drv.c    |    8 ++++----
 3 files changed, 10 insertions(+), 8 deletions(-)
drivers/hv/hv.c +5 -3
@@ -274,7 +274,7 @@ cleanup:
  *
  * This routine is called normally during driver unloading or exiting.
  */
-void hv_cleanup(void)
+void hv_cleanup(bool crash)
 {
 	union hv_x64_msr_hypercall_contents hypercall_msr;
 

@@ -284,7 +284,8 @@ void hv_cleanup(void)
 	if (hv_context.hypercall_page) {
 		hypercall_msr.as_uint64 = 0;
 		wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
-		vfree(hv_context.hypercall_page);
+		if (!crash)
+			vfree(hv_context.hypercall_page);
 		hv_context.hypercall_page = NULL;
 	}
 

@@ -304,7 +305,8 @@ void hv_cleanup(void)
 
 		hypercall_msr.as_uint64 = 0;
 		wrmsrl(HV_X64_MSR_REFERENCE_TSC, hypercall_msr.as_uint64);
-		vfree(hv_context.tsc_page);
+		if (!crash)
+			vfree(hv_context.tsc_page);
 		hv_context.tsc_page = NULL;
 	}
 #endif
drivers/hv/hyperv_vmbus.h +1 -1
@@ -581,7 +581,7 @@ struct hv_ring_buffer_debug_info {
 
 extern int hv_init(void);
 
-extern void hv_cleanup(void);
+extern void hv_cleanup(bool crash);
 
 extern int hv_post_message(union hv_connection_id connection_id,
 			 enum hv_message_type message_type,
drivers/hv/vmbus_drv.c +4 -4
@@ -889,7 +889,7 @@ err_alloc:
 	bus_unregister(&hv_bus);
 
 err_cleanup:
-	hv_cleanup();
+	hv_cleanup(false);
 
 	return ret;
 }

@@ -1254,7 +1254,7 @@ static void hv_kexec_handler(void)
 	vmbus_initiate_unload();
 	for_each_online_cpu(cpu)
 		smp_call_function_single(cpu, hv_synic_cleanup, NULL, 1);
-	hv_cleanup();
+	hv_cleanup(false);
 };
 
 static void hv_crash_handler(struct pt_regs *regs)

@@ -1266,7 +1266,7 @@ static void hv_crash_handler(struct pt_r
 	 * for kdump.
 	 */
 	hv_synic_cleanup(NULL);
-	hv_cleanup();
+	hv_cleanup(true);
 };
 
 static int __init hv_acpi_init(void)

@@ -1330,7 +1330,7 @@ static void __exit vmbus_exit(void)
 						 &hyperv_panic_block);
 	}
 	bus_unregister(&hv_bus);
-	hv_cleanup();
+	hv_cleanup(false);
 	for_each_online_cpu(cpu) {
 		tasklet_kill(hv_context.event_dpc[cpu]);
 		smp_call_function_single(cpu, hv_synic_cleanup, NULL, 1);

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/drivers-hv-balloon-don-t-crash-when-memory-is-added-in-non-sorted-order.patch queue-4.4/drivers-hv-avoid-vfree-on-crash.patch queue-4.4/hv_netvsc-use-skb_get_hash-instead-of-a-homegrown-implementation.patch