| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2024-44991: tcp: prevent concurrent execution of tcp_sk_exit_batch |
| |
| Description |
| =========== |
| |
| 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->ipv4.tcp_death_row.tw_refcount)); |
| |
| without the expected 1 -> 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. |
| |
| The Linux kernel CVE team has assigned CVE-2024-44991 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 6.1 with commit e9bd0cca09d13ac2f08d25e195203e42d4ad1ce8 and fixed in 6.1.107 with commit e3d9de3742f4d5c47ae35f888d3023a5b54fcd2f |
| Issue introduced in 6.1 with commit e9bd0cca09d13ac2f08d25e195203e42d4ad1ce8 and fixed in 6.6.48 with commit 99580ae890ec8bd98b21a2a9c6668f8f1555b62e |
| Issue introduced in 6.1 with commit e9bd0cca09d13ac2f08d25e195203e42d4ad1ce8 and fixed in 6.10.7 with commit f6fd2dbf584a4047ba88d1369ff91c9851261ec1 |
| Issue introduced in 6.1 with commit e9bd0cca09d13ac2f08d25e195203e42d4ad1ce8 and fixed in 6.11 with commit 565d121b69980637f040eb4d84289869cdaabedf |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2024-44991 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| net/ipv4/tcp_ipv4.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/e3d9de3742f4d5c47ae35f888d3023a5b54fcd2f |
| https://git.kernel.org/stable/c/99580ae890ec8bd98b21a2a9c6668f8f1555b62e |
| https://git.kernel.org/stable/c/f6fd2dbf584a4047ba88d1369ff91c9851261ec1 |
| https://git.kernel.org/stable/c/565d121b69980637f040eb4d84289869cdaabedf |
