From: Yanming Liu yanminglr@gmail.com
[ Upstream commit 96d9d1fa5cd505078534113308ced0aa56d8da58 ]
Commit adae1e931acd ("Drivers: hv: vmbus: Copy packets sent by Hyper-V out of the ring buffer") introduced a notion of maximum packet size in vmbus channel and used that size to initialize a buffer holding all incoming packet along with their vmbus packet header. hv_balloon uses the default maximum packet size VMBUS_DEFAULT_MAX_PKT_SIZE which matches its maximum message size, however vmbus_open expects this size to also include vmbus packet header. This leads to 4096 bytes dm_unballoon_request messages being truncated to 4080 bytes. When the driver tries to read next packet it starts from a wrong read_index, receives garbage and prints a lot of "Unhandled message: type: <garbage>" in dmesg.
Allocate the buffer with HV_HYP_PAGE_SIZE more bytes to make room for the header.
Fixes: adae1e931acd ("Drivers: hv: vmbus: Copy packets sent by Hyper-V out of the ring buffer") Suggested-by: Michael Kelley (LINUX) mikelley@microsoft.com Suggested-by: Andrea Parri (Microsoft) parri.andrea@gmail.com Signed-off-by: Yanming Liu yanminglr@gmail.com Reviewed-by: Michael Kelley mikelley@microsoft.com Reviewed-by: Andrea Parri (Microsoft) parri.andrea@gmail.com Link: https://lore.kernel.org/r/20220119202052.3006981-1-yanminglr@gmail.com Signed-off-by: Wei Liu wei.liu@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/hv/hv_balloon.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c index ca873a3b98dbe..f2d05bff42453 100644 --- a/drivers/hv/hv_balloon.c +++ b/drivers/hv/hv_balloon.c @@ -1660,6 +1660,13 @@ static int balloon_connect_vsp(struct hv_device *dev) unsigned long t; int ret;
+ /* + * max_pkt_size should be large enough for one vmbus packet header plus + * our receive buffer size. Hyper-V sends messages up to + * HV_HYP_PAGE_SIZE bytes long on balloon channel. + */ + dev->channel->max_pkt_size = HV_HYP_PAGE_SIZE * 2; + ret = vmbus_open(dev->channel, dm_ring_size, dm_ring_size, NULL, 0, balloon_onchannelcallback, dev); if (ret)