# CVE-2021-47162: linux: In the Linux kernel, the following vulnerability has been resolved: tipc: skb_linearize the head skb when reassembli... CVE-2021-47162 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47162, released March 25, 2024. It is not reported as exploited. Patch Radar priority: Routine. - Web page: https://patchblox.com/security/cve/CVE-2021-47162 - Priority: Routine - CVSS: 5.5 (medium) - EPSS: 0.0074 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Mar 25, 2024 ## Description 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: [] [] 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. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | linux Debian 12.15 (bookworm) | 5.14.6-1 | [DEBIAN-CVE-2021-47162](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47162.md) | Mar 25, 2024 | | Linux | linux Debian 13.5 (trixie) | 5.14.6-1 | [DEBIAN-CVE-2021-47162](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47162.md) | Mar 25, 2024 | | Linux | linux Debian 14 | 5.14.6-1 | [DEBIAN-CVE-2021-47162](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47162.md) | Mar 25, 2024 | --- Data as of 2026-11-08T13:06:02Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.