On 8/27/19 23:45, Srinivas Kandagatla wrote: > > On 23/08/2019 16:23, Jorge Ramirez-Ortiz wrote: >> can you add me as a co-author to this patch please? > > No problem I can do that if you feel so! yes please. thanks! > >> since I spent about a day doing the analysis, sent you a fix that >> maintained the API used by the library and explained you how to >> reproduce the issue I think it is just fair. > the fact that the api >> could be be modified and the fix be done a bit >> differently- free dma buf ioctl removed- seems just a minor >> implementation detail to me. > > No, that's not true, this is a clear fastrpc design issue. IMO the ioctls defines the contract with userspace and the contract establishes that userspace must call deallocate. the kernel wrongly implemented to that contract since it doesn't handle the cases where userspace can't send the release calls which leads to memory leaks. this is what I meant by and implementation issue. if we had many fastrpc users, rolling out the design change that you propose - removing an ioctl- would definitively have an impact. But since that is not yet the case, there is not doubt that your patch makes more sense. but my point was that there is not a huge gap in efforts between doing one or the other. > > Userspace is already doing a refcount via mmap/unmap on that dmabuf fd, > having an additional api adds another level of refcount which is totally > redundant and is the root cause for this leak. yes it is redundant but is not the root cause for this leak. the root cause is that the driver doesnt handle the case where userspace didnt or was not able to call release (and that is no more than adding allocated buffers to a list and clean on exit) > > > --srini
