#27813: Tor 0.3.4.8 is leaking memory -------------------------------------------------+------------------------- Reporter: anong | Owner: (none) Type: defect | Status: | needs_information Priority: Very High | Milestone: Tor: | 0.3.5.x-final Component: Core Tor/Tor | Version: Tor: | 0.3.4.8 Severity: Critical | Resolution: Keywords: regression? memleak oom | Actual Points: 034-backport tor-relay 035-must | Parent ID: | Points: Reviewer: | Sponsor: -------------------------------------------------+-------------------------
Comment (by dgoulet): Replying to [comment:29 starlight]: > Reading this ticket and #28089 a potential concern comes to mind. In my experience the Linux kernel is fastidious in releasing skb memory when sockets close, which leads to the question: is an additional bug present in KIST where sockets are leaked? For kernel memory consumption to grow unbounded while the relay daemon continues to function correctly, a socket leak or stranding would appear necessary. I do not know this code and someone familiar with it would be in a better position to consider the possibility. KIST doesn't manage sockets. It is a scheduler that only relays cell based on kernel information per-socket and trying to be fair by considering all circuits. The issue here is clearly the fact that one side of the connection (relay to relay) wasn't reading on the socket which caused the TCP window to shrink down to 0 and thus the other side queuing cells in the Kernel. That explains why nobody sees the memory leak in userspace by looking at tor's memory. KIST should prevent that in theory but not entirely. Some could always go as in flushing 1M of cells and only one goes through leaving the rest in the kernel. The bigger issue is that we still have cells bypassing the KIST scheduler that are directly written on the socket. We have several ticket open about these issues. -- Ticket URL: <https://trac.torproject.org/projects/tor/ticket/27813#comment:30> Tor Bug Tracker & Wiki <https://trac.torproject.org/> The Tor Project: anonymity online
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