Use After Free Affecting kernel-rt-modules package, versions *
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-RHEL8-KERNELRTMODULES-6489150
- published26 Mar 2024
- disclosed25 Mar 2024
Introduced: 25 Mar 2024
CVE-2021-47162 (opens in a new tab)How to fix?
There is no fixed version for RHEL:8 kernel-rt-modules.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-rt-modules package and not the kernel-rt-modules package as distributed by RHEL.
See How to fix? for RHEL:8 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
tipc: skb_linearize the head skb when reassembling msgs
It's not a good idea to append the frag skb to a skb's frag_list if the frag_list already has skbs from elsewhere, such as this skb was created by pskb_copy() where the frag_list was cloned (all the skbs in it were skb_get'ed) and shared by multiple skbs.
However, the new appended frag skb should have been only seen by the current skb. Otherwise, it will cause use after free crashes as this appended frag skb are seen by multiple skbs but it only got skb_get called once.
The same thing happens with a skb updated by pskb_may_pull() with a skb_cloned skb. Li Shuang has reported quite a few crashes caused by this when doing testing over macvlan devices:
[] kernel BUG at net/core/skbuff.c:1970! [] Call Trace: [] skb_clone+0x4d/0xb0 [] macvlan_broadcast+0xd8/0x160 [macvlan] [] macvlan_process_broadcast+0x148/0x150 [macvlan] [] process_one_work+0x1a7/0x360 [] worker_thread+0x30/0x390
[] kernel BUG at mm/usercopy.c:102! [] Call Trace: [] __check_heap_object+0xd3/0x100 [] __check_object_size+0xff/0x16b [] simple_copy_to_iter+0x1c/0x30 [] __skb_datagram_iter+0x7d/0x310 [] __skb_datagram_iter+0x2a5/0x310 [] skb_copy_datagram_iter+0x3b/0x90 [] tipc_recvmsg+0x14a/0x3a0 [tipc] [] ____sys_recvmsg+0x91/0x150 [] ___sys_recvmsg+0x7b/0xc0
[] kernel BUG at mm/slub.c:305! [] Call Trace: [] <IRQ> [] kmem_cache_free+0x3ff/0x400 [] __netif_receive_skb_core+0x12c/0xc40 [] ? kmem_cache_alloc+0x12e/0x270 [] netif_receive_skb_internal+0x3d/0xb0 [] ? get_rx_page_info+0x8e/0xa0 [be2net] [] be_poll+0x6ef/0xd00 [be2net] [] ? irq_exit+0x4f/0x100 [] net_rx_action+0x149/0x3b0
...
This patch is to fix it by linearizing the head skb if it has frag_list set in tipc_buf_append(). Note that we choose to do this before calling skb_unshare(), as __skb_linearize() will avoid skb_copy(). Also, we can not just drop the frag_list either as the early time.
References
- https://access.redhat.com/security/cve/CVE-2021-47162
- https://git.kernel.org/stable/c/436d650d374329a591c30339a91fa5078052ed1e
- https://git.kernel.org/stable/c/4b1761898861117c97066aea6c58f68a7787f0bf
- https://git.kernel.org/stable/c/5489f30bb78ff0dafb4229a69632afc2ba20765c
- https://git.kernel.org/stable/c/64d17ec9f1ded042c4b188d15734f33486ed9966
- https://git.kernel.org/stable/c/6da24cfc83ba4f97ea44fc7ae9999a006101755c
- https://git.kernel.org/stable/c/ace300eecbccaa698e2b472843c74a5f33f7dce8
- https://git.kernel.org/stable/c/b2c8d28c34b3070407cb1741f9ba3f15d0284b8b
- https://git.kernel.org/stable/c/b7df21cf1b79ab7026f545e7bf837bd5750ac026