{"id":"DEBIAN-CVE-2024-44991","details":"In the Linux kernel, the following vulnerability has been resolved:  tcp: prevent concurrent execution of tcp_sk_exit_batch  Its possible that two threads call tcp_sk_exit_batch() concurrently, once from the cleanup_net workqueue, once from a task that failed to clone a new netns.  In the latter case, error unwinding calls the exit handlers in reverse order for the 'failed' netns.  tcp_sk_exit_batch() calls tcp_twsk_purge(). Problem is that since commit b099ce2602d8 (\"net: Batch inet_twsk_purge\"), this function picks up twsk in any dying netns, not just the one passed in via exit_batch list.  This means that the error unwind of setup_net() can \"steal\" and destroy timewait sockets belonging to the exiting netns.  This allows the netns exit worker to proceed to call  WARN_ON_ONCE(!refcount_dec_and_test(&net-\u003eipv4.tcp_death_row.tw_refcount));  without the expected 1 -\u003e 0 transition, which then splats.  At same time, error unwind path that is also running inet_twsk_purge() will splat as well:  WARNING: .. at lib/refcount.c:31 refcount_warn_saturate+0x1ed/0x210 ...  refcount_dec include/linux/refcount.h:351 [inline]  inet_twsk_kill+0x758/0x9c0 net/ipv4/inet_timewait_sock.c:70  inet_twsk_deschedule_put net/ipv4/inet_timewait_sock.c:221  inet_twsk_purge+0x725/0x890 net/ipv4/inet_timewait_sock.c:304  tcp_sk_exit_batch+0x1c/0x170 net/ipv4/tcp_ipv4.c:3522  ops_exit_list+0x128/0x180 net/core/net_namespace.c:178  setup_net+0x714/0xb40 net/core/net_namespace.c:375  copy_net_ns+0x2f0/0x670 net/core/net_namespace.c:508  create_new_namespaces+0x3ea/0xb10 kernel/nsproxy.c:110  ... because refcount_dec() of tw_refcount unexpectedly dropped to 0.  This doesn't seem like an actual bug (no tw sockets got lost and I don't see a use-after-free) but as erroneous trigger of debug check.  Add a mutex to force strict ordering: the task that calls tcp_twsk_purge() blocks other task from doing final _dec_and_test before mutex-owner has removed all tw sockets of dying netns.","modified":"2026-09-15T09:03:10.961590970Z","published":"2024-09-04T20:15:08.150Z","upstream":["CVE-2024-44991"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2024-44991"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.112-1"}]}],"versions":["6.1.106-1","6.1.106-2","6.1.106-3","6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1","6.1.99-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-44991.json"}},{"package":{"name":"linux","ecosystem":"Debian:13","purl":"pkg:deb/debian/linux?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.10.7-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-44991.json"}},{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.10.7-1"}]}],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2024-44991.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"}]}