On Sun, 2021-03-14 at 13:44 +0100, Greg KH wrote: > On Sun, Mar 14, 2021 at 03:19:05PM +0300, Fatih Yildirim wrote: > > On Sun, 2021-03-14 at 09:36 +0100, Greg KH wrote: > > > On Sun, Mar 14, 2021 at 11:23:10AM +0300, Fatih Yildirim wrote: > > > > Hi Santosh, > > > > > > > > I've been working on a memory leak bug reported by syzbot. > > > > https://syzkaller.appspot.com/bug?id=39b72114839a6dbd66c1d2104522698a813f9ae2 > > > > > > > > It seems that memory allocated in rds_send_probe function is > > > > not > > > > freed. > > > > > > > > Let me share my observations. > > > > rds_message is allocated at the beginning of rds_send_probe > > > > function. > > > > Then it is added to cp_send_queue list of rds_conn_path and > > > > refcount > > > > is increased by one. > > > > Next, in rds_send_xmit function it is moved from cp_send_queue > > > > list > > > > to > > > > cp_retrans list, and again refcount is increased by one. > > > > Finally in rds_loop_xmit function refcount is increased by one. > > > > So, total refcount is 4. > > > > However, rds_message_put is called three times, in > > > > rds_send_probe, > > > > rds_send_remove_from_sock and rds_send_xmit functions. It seems > > > > that > > > > one more rds_message_put is needed. > > > > Would you please check and share your comments on this issue? > > > > > > Do you have a proposed patch that syzbot can test to verify if > > > this > > > is > > > correct or not? > > > > > > thanks, > > > > > > gre gk-h > > > > Hi Greg, > > > > Actually, using the .config and the C reproducer, syzbot reports > > the > > memory leak in rds_send_probe function. Also by enabling > > CONFIG_RDS_DEBUG=y, the debug messages indicates the similar as I > > mentioned above. To give an example, below is the RDS_DEBUG > > messages. > > Allocated address 000000008a7476e5 has initial ref_count 1. Then > > there > > are three rds_message_addref calls for the same address making the > > refcount 4, but only three rds_message_put calls which leave the > > address still allocated. > > > > [ 60.570681] rds_message_addref(): addref rm 000000008a7476e5 ref > > 1 > > [ 60.570707] rds_message_put(): put rm 000000008a7476e5 ref 2 > > [ 60.570845] rds_message_addref(): addref rm 000000008a7476e5 ref > > 1 > > [ 60.570870] rds_message_addref(): addref rm 000000008a7476e5 ref > > 2 > > [ 60.570960] rds_message_put(): put rm 000000008a7476e5 ref 3 > > [ 60.570995] rds_message_put(): put rm 000000008a7476e5 ref 2 > > > > Ok, so the next step is to try your proposed change to see if it > works > or not. What prevents you from doign that? > > No need to ask people if your analysis of an issue is true or not, no > maintainer or developer usually has the time to deal with that. We > much > rather would like to see patches of things you have tested to resolve > issues. > > thanks, > > greg k-h Hi Greg, I also would like to come with a patch to resolve the issue as well. But couldn't figure out so far. I just would like to have a review or a suggestion from an expert in order to move forward. Anyway, I'm still working on it and hope to find a solution. Will appreciate any comment, suggestion on the issue. Thanks, Fatih
