| 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-2021-46936: net: fix use-after-free in tw_timer_handler |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| net: fix use-after-free in tw_timer_handler |
| |
| A real world panic issue was found as follow in Linux 5.4. |
| |
| BUG: unable to handle page fault for address: ffffde49a863de28 |
| PGD 7e6fe62067 P4D 7e6fe62067 PUD 7e6fe63067 PMD f51e064067 PTE 0 |
| RIP: 0010:tw_timer_handler+0x20/0x40 |
| Call Trace: |
| <IRQ> |
| call_timer_fn+0x2b/0x120 |
| run_timer_softirq+0x1ef/0x450 |
| __do_softirq+0x10d/0x2b8 |
| irq_exit+0xc7/0xd0 |
| smp_apic_timer_interrupt+0x68/0x120 |
| apic_timer_interrupt+0xf/0x20 |
| |
| This issue was also reported since 2017 in the thread [1], |
| unfortunately, the issue was still can be reproduced after fixing |
| DCCP. |
| |
| The ipv4_mib_exit_net is called before tcp_sk_exit_batch when a net |
| namespace is destroyed since tcp_sk_ops is registered befrore |
| ipv4_mib_ops, which means tcp_sk_ops is in the front of ipv4_mib_ops |
| in the list of pernet_list. There will be a use-after-free on |
| net->mib.net_statistics in tw_timer_handler after ipv4_mib_exit_net |
| if there are some inflight time-wait timers. |
| |
| This bug is not introduced by commit f2bf415cfed7 ("mib: add net to |
| NET_ADD_STATS_BH") since the net_statistics is a global variable |
| instead of dynamic allocation and freeing. Actually, commit |
| 61a7e26028b9 ("mib: put net statistics on struct net") introduces |
| the bug since it put net statistics on struct net and free it when |
| net namespace is destroyed. |
| |
| Moving init_ipv4_mibs() to the front of tcp_init() to fix this bug |
| and replace pr_crit() with panic() since continuing is meaningless |
| when init_ipv4_mibs() fails. |
| |
| [1] https://groups.google.com/g/syzkaller/c/p1tn-_Kc6l4/m/smuL_FMAAgAJ?pli=1 |
| |
| The Linux kernel CVE team has assigned CVE-2021-46936 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 2.6.27 with commit 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 and fixed in 4.4.298 with commit 15579e1301f856ad9385d720c9267c11032a5022 |
| Issue introduced in 2.6.27 with commit 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 and fixed in 4.9.296 with commit e73164e89d1be561228a4534e1091369ee4ba41a |
| Issue introduced in 2.6.27 with commit 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 and fixed in 4.14.261 with commit 5c2fe20ad37ff56070ae0acb34152333976929b4 |
| Issue introduced in 2.6.27 with commit 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 and fixed in 4.19.224 with commit a8e1944b44f94f5c5f530e434c5eaee787254566 |
| Issue introduced in 2.6.27 with commit 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 and fixed in 5.4.170 with commit fe5838c22b986c1190f1dce9aa09bf6a491c1a69 |
| Issue introduced in 2.6.27 with commit 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 and fixed in 5.10.90 with commit 2386e81a1d277f540e1285565c9d41d531bb69d4 |
| Issue introduced in 2.6.27 with commit 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 and fixed in 5.15.13 with commit 08eacbd141e2495d2fcdde84358a06c4f95cbb13 |
| Issue introduced in 2.6.27 with commit 61a7e26028b94805fd686a6dc9dbd9941f8f19b0 and fixed in 5.16 with commit e22e45fc9e41bf9fcc1e92cfb78eb92786728ef0 |
| |
| 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-2021-46936 |
| 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/af_inet.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/15579e1301f856ad9385d720c9267c11032a5022 |
| https://git.kernel.org/stable/c/e73164e89d1be561228a4534e1091369ee4ba41a |
| https://git.kernel.org/stable/c/5c2fe20ad37ff56070ae0acb34152333976929b4 |
| https://git.kernel.org/stable/c/a8e1944b44f94f5c5f530e434c5eaee787254566 |
| https://git.kernel.org/stable/c/fe5838c22b986c1190f1dce9aa09bf6a491c1a69 |
| https://git.kernel.org/stable/c/2386e81a1d277f540e1285565c9d41d531bb69d4 |
| https://git.kernel.org/stable/c/08eacbd141e2495d2fcdde84358a06c4f95cbb13 |
| https://git.kernel.org/stable/c/e22e45fc9e41bf9fcc1e92cfb78eb92786728ef0 |
