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
History

Wed, 11 Sep 2024 18:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 11 Sep 2024 13:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2024-02-27T09:44:02.758Z

Updated: 2024-09-11T17:33:18.637Z

Reserved: 2024-02-25T13:45:52.720Z

Link: CVE-2021-46936

cve-icon Vulnrichment

Updated: 2024-08-04T05:17:42.878Z

cve-icon NVD

Status : Analyzed

Published: 2024-02-27T10:15:08.017

Modified: 2024-04-10T19:20:08.790

Link: CVE-2021-46936

cve-icon Redhat

Severity : Moderate

Publid Date: 2024-02-27T00:00:00Z

Links: CVE-2021-46936 - Bugzilla