Description (CNA)
In the Linux kernel, the following vulnerability has been resolved: inet: frags: flush pending skbs in fqdir_pre_exit() We have been seeing occasional deadlocks on pernet_ops_rwsem since September in NIPA. The stuck task was usually modprobe (often loading a driver like ipvlan), trying to take the lock as a Writer. lockdep does not track readers for rwsems so the read wasn't obvious from the reports. On closer inspection the Reader holding the lock was conntrack looping forever in nf_conntrack_cleanup_net_list(). Based on past experience with occasional NIPA crashes I looked thru the tests which run before the crash and noticed that the crash follows ip_defrag.sh. An immediate red flag. Scouring thru (de)fragmentation queues reveals skbs sitting around, holding conntrack references. The problem is that since conntrack depends on nf_defrag_ipv6, nf_defrag_ipv6 will load first. Since nf_defrag_ipv6 loads first its netns exit hooks run _after_ conntrack's netns exit hook. Flush all fragment queue SKBs during fqdir_pre_exit() to release conntrack references before conntrack cleanup runs. Also flush the queues in timer expiry handlers when they discover fqdir->dead is set, in case packet sneaks in while we're running the pre_exit flush. The commit under Fixes is not exactly the culprit, but I think previously the timer firing would eventually unblock the spinning conntrack.
Affected (CNA)
| Vendor / product | Versions |
|---|---|
| Linux / Linux | affected d5dd88794a13c2f24cce31abad7a0a6c5e0ed2db before 22ee4010866da81aeee08e1ea3fddbe418feb212; affected d5dd88794a13c2f24cce31abad7a0a6c5e0ed2db before 543555954b1ee8d1903a7020324efb41b0c97428; affected d5dd88794a13c2f24cce31abad7a0a6c5e0ed2db before c70df25214ac9b32b53e18e6ae3b8f073ffa6903; affected d5dd88794a13c2f24cce31abad7a0a6c5e0ed2db before 006a5035b495dec008805df249f92c22c89c3d2e |
| Linux / Linux | affected 5.3; unaffected 0 before 5.3; unaffected 6.6.143 through 6.6.*; unaffected 6.12.93 through 6.12.*; unaffected 6.18.3 through 6.18.*; unaffected 6.19 through * |
CWE
No CWE identifiers supplied.