CVE-2024-43887 (GCVE-0-2024-43887)

Vulnerability from cvelistv5 – Published: 2024-08-26 10:10 – Updated: 2025-05-04 09:28
VLAI?
Title
net/tcp: Disable TCP-AO static key after RCU grace period
Summary
In the Linux kernel, the following vulnerability has been resolved: net/tcp: Disable TCP-AO static key after RCU grace period The lifetime of TCP-AO static_key is the same as the last tcp_ao_info. On the socket destruction tcp_ao_info ceases to be with RCU grace period, while tcp-ao static branch is currently deferred destructed. The static key definition is : DEFINE_STATIC_KEY_DEFERRED_FALSE(tcp_ao_needed, HZ); which means that if RCU grace period is delayed by more than a second and tcp_ao_needed is in the process of disablement, other CPUs may yet see tcp_ao_info which atent dead, but soon-to-be. And that breaks the assumption of static_key_fast_inc_not_disabled(). See the comment near the definition: > * The caller must make sure that the static key can't get disabled while > * in this function. It doesn't patch jump labels, only adds a user to > * an already enabled static key. Originally it was introduced in commit eb8c507296f6 ("jump_label: Prevent key->enabled int overflow"), which is needed for the atomic contexts, one of which would be the creation of a full socket from a request socket. In that atomic context, it's known by the presence of the key (md5/ao) that the static branch is already enabled. So, the ref counter for that static branch is just incremented instead of holding the proper mutex. static_key_fast_inc_not_disabled() is just a helper for such usage case. But it must not be used if the static branch could get disabled in parallel as it's not protected by jump_label_mutex and as a result, races with jump_label_update() implementation details. Happened on netdev test-bot[1], so not a theoretical issue: [] jump_label: Fatal kernel bug, unexpected op at tcp_inbound_hash+0x1a7/0x870 [ffffffffa8c4e9b7] (eb 50 0f 1f 44 != 66 90 0f 1f 00)) size:2 type:1 [] ------------[ cut here ]------------ [] kernel BUG at arch/x86/kernel/jump_label.c:73! [] Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI [] CPU: 3 PID: 243 Comm: kworker/3:3 Not tainted 6.10.0-virtme #1 [] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [] Workqueue: events jump_label_update_timeout [] RIP: 0010:__jump_label_patch+0x2f6/0x350 ... [] Call Trace: [] <TASK> [] arch_jump_label_transform_queue+0x6c/0x110 [] __jump_label_update+0xef/0x350 [] __static_key_slow_dec_cpuslocked.part.0+0x3c/0x60 [] jump_label_update_timeout+0x2c/0x40 [] process_one_work+0xe3b/0x1670 [] worker_thread+0x587/0xce0 [] kthread+0x28a/0x350 [] ret_from_fork+0x31/0x70 [] ret_from_fork_asm+0x1a/0x30 [] </TASK> [] Modules linked in: veth [] ---[ end trace 0000000000000000 ]--- [] RIP: 0010:__jump_label_patch+0x2f6/0x350 [1]: https://netdev-3.bots.linux.dev/vmksft-tcp-ao-dbg/results/696681/5-connect-deny-ipv6/stderr
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 67fa83f7c86a86913ab9cd5a13b4bebd8d2ebb43 , < 954d55a59b2501f4a9bd693b40ce45a1c46cb2b3 (git)
Affected: 67fa83f7c86a86913ab9cd5a13b4bebd8d2ebb43 , < 14ab4792ee120c022f276a7e4768f4dcb08f0cdd (git)
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    Linux Linux Affected: 6.7
Unaffected: 0 , < 6.7 (semver)
Unaffected: 6.10.5 , ≤ 6.10.* (semver)
Unaffected: 6.11 , ≤ * (original_commit_for_fix)
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On the socket destruction tcp_ao_info ceases to be\\nwith RCU grace period, while tcp-ao static branch is currently deferred\\ndestructed. The static key definition is\\n: DEFINE_STATIC_KEY_DEFERRED_FALSE(tcp_ao_needed, HZ);\\n\\nwhich means that if RCU grace period is delayed by more than a second\\nand tcp_ao_needed is in the process of disablement, other CPUs may\\nyet see tcp_ao_info which atent dead, but soon-to-be.\\nAnd that breaks the assumption of static_key_fast_inc_not_disabled().\\n\\nSee the comment near the definition:\\n\u003e * The caller must make sure that the static key can\u0027t get disabled while\\n\u003e * in this function. It doesn\u0027t patch jump labels, only adds a user to\\n\u003e * an already enabled static key.\\n\\nOriginally it was introduced in commit eb8c507296f6 (\\\"jump_label:\\nPrevent key-\u003eenabled int overflow\\\"), which is needed for the atomic\\ncontexts, one of which would be the creation of a full socket from a\\nrequest socket. 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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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