From: Michael Kelley <[email protected]> Sent: Thursday, September 3, 2026 9:07 AM > > When a Hyper-V netvsc device is shutdown, the GPADLs for the device's > large send and receive buffers are torn down. If the teardown fails, > Hyper-V retain access to the buffers and may continue to read or write > them. Consequently the buffers should be leaked after such an error. > > Leaking the buffers used to work correctly, but was broken by a > commit applied in the 4.16 kernel. This patch series restores the > correct leaking behavior. > > Because the large buffers are allocated with wrapper functions > that allow allocations larger than MAX_ORDER_NR_PAGES, leaking the > memory is not as simple as setting the memory pointer to NULL so > vfree() or kfree() does nothing. Patch 1 introduces a new > vmbus_leak_buffer() function that causes vmbus_free_buffer() to > properly leak the buffers. Then Patch 2 uses this function in > the netvsc driver. > > Michael Kelley (2): > Drivers: hv: Add vmbus_leak_buffer() > hv_netvsc: Leak send/recv buffers if GPADL teardown fails > > drivers/hv/channel.c | 26 ++++++++++++++++++++++++++ > drivers/net/hyperv/netvsc.c | 6 ++++++ > include/linux/hyperv.h | 4 ++++ > 3 files changed, 36 insertions(+) > > -- > 2.25.1 >
I will be posting a v2 of this patch set that fixes an additional bug in vmbus_teardown_gpadl() that Sashiko pointed out. That fix is necessary for the full "leak on failure" scenario to work correctly. Michael
