On 6/19/23 3:57?AM, Stefan Metzmacher wrote: > Hi Jens, > >> If the application sets ->msg_control and we have to later retry this >> command, or if it got queued with IOSQE_ASYNC to begin with, then we >> need to retain the original msg_control value. This is due to the net >> stack overwriting this field with an in-kernel pointer, to copy it >> in. Hitting that path for the second time will now fail the copy from >> user, as it's attempting to copy from a non-user address. > > I'm not 100% sure about the impact of this change. > > But I think the logic we need is that only the > first __sys_sendmsg_sock() that returns > 0 should > see msg_control. A retry because of MSG_WAITALL should > clear msg_control[len] for a follow up __sys_sendmsg_sock(). > And I fear the patch below would not clear it... > > Otherwise the receiver/socket-layer will get the same msg_control twice, > which is unexpected. Yes agree, if we do transfer some (but not all) data and WAITALL is set, it should get cleared. I'll post a patch for that. Note that it was also broken before, just differently broken. The most likely outcome here was a full retry and now getting -EFAULT. -- Jens Axboe
