{ "schema_version": "1.6.1", "id": "RPI-CVE-2024-41048", "modified": "2026-10-09T11:39:44Z", "upstream": [ "CVE-2024-41048" ], "published": "2024-07-29T14:32:49Z", "summary": "skmsg: Skip zero length skb in sk_msg_recvmsg", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nskmsg: Skip zero length skb in sk_msg_recvmsg\n\nWhen running BPF selftests (./test_progs -t sockmap_basic) on a Loongarch\nplatform, the following kernel panic occurs:\n\n [...]\n Oops[#1]:\n CPU: 22 PID: 2824 Comm: test_progs Tainted: G OE 6.10.0-rc2+ #18\n Hardware name: LOONGSON Dabieshan/Loongson-TC542F0, BIOS Loongson-UDK2018\n ... ...\n ra: 90000000048bf6c0 sk_msg_recvmsg+0x120/0x560\n ERA: 9000000004162774 copy_page_to_iter+0x74/0x1c0\n CRMD: 000000b0 (PLV0 -IE -DA +PG DACF=CC DACM=CC -WE)\n PRMD: 0000000c (PPLV0 +PIE +PWE)\n EUEN: 00000007 (+FPE +SXE +ASXE -BTE)\n ECFG: 00071c1d (LIE=0,2-4,10-12 VS=7)\n ESTAT: 00010000 [PIL] (IS= ECode=1 EsubCode=0)\n BADV: 0000000000000040\n PRID: 0014c011 (Loongson-64bit, Loongson-3C5000)\n Modules linked in: bpf_testmod(OE) xt_CHECKSUM xt_MASQUERADE xt_conntrack\n Process test_progs (pid: 2824, threadinfo=0000000000863a31, task=...)\n Stack : ...\n Call Trace:\n [<9000000004162774>] copy_page_to_iter+0x74/0x1c0\n [<90000000048bf6c0>] sk_msg_recvmsg+0x120/0x560\n [<90000000049f2b90>] tcp_bpf_recvmsg_parser+0x170/0x4e0\n [<90000000049aae34>] inet_recvmsg+0x54/0x100\n [<900000000481ad5c>] sock_recvmsg+0x7c/0xe0\n [<900000000481e1a8>] __sys_recvfrom+0x108/0x1c0\n [<900000000481e27c>] sys_recvfrom+0x1c/0x40\n [<9000000004c076ec>] do_syscall+0x8c/0xc0\n [<9000000003731da4>] handle_syscall+0xc4/0x160\n Code: ...\n ---[ end trace 0000000000000000 ]---\n Kernel panic - not syncing: Fatal exception\n Kernel relocated by 0x3510000\n .text @ 0x9000000003710000\n .data @ 0x9000000004d70000\n .bss @ 0x9000000006469400\n ---[ end Kernel panic - not syncing: Fatal exception ]---\n [...]\n\nThis crash happens every time when running sockmap_skb_verdict_shutdown\nsubtest in sockmap_basic.\n\nThis crash is because a NULL pointer is passed to page_address() in the\nsk_msg_recvmsg(). Due to the different implementations depending on the\narchitecture, page_address(NULL) will trigger a panic on Loongarch\nplatform but not on x86 platform. So this bug was hidden on x86 platform\nfor a while, but now it is exposed on Loongarch platform. The root cause\nis that a zero length skb (skb->len == 0) was put on the queue.\n\nThis zero length skb is a TCP FIN packet, which was sent by shutdown(),\ninvoked in test_sockmap_skb_verdict_shutdown():\n\n\tshutdown(p1, SHUT_WR);\n\nIn this case, in sk_psock_skb_ingress_enqueue(), num_sge is zero, and no\npage is put to this sge (see sg_set_page in sg_set_page), but this empty\nsge is queued into ingress_msg list.\n\nAnd in sk_msg_recvmsg(), this empty sge is used, and a NULL page is got by\nsg_page(sge). Pass this NULL page to copy_page_to_iter(), which passes it\nto kmap_local_page() and to page_address(), then kernel panics.\n\nTo solve this, we should skip this zero length skb. So in sk_msg_recvmsg(),\nif copy is zero, that means it's a zero length skb, skip invoking\ncopy_page_to_iter(). We are using the EFAULT return triggered by\ncopy_page_to_iter to check for is_fin in tcp_bpf.c.", "severity": [ { "type": "CVSS_V3", "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H" } ], "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:12", "name": "linux" }, "versions": [ "1:6.1.21-1+rpt1", "1:6.1.47-1+rpt2", "1:6.1.47-1+rpt4", "1:6.1.54-1+rpt2", "1:6.1.58-1+rpt2", "1:6.1.63-1+rpt1", "1:6.1.73-1+rpt1", "1:6.6.20-1+rpt1", "1:6.6.28-1+rpt1", "1:6.6.31-1+rpt1" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.1.0-rpi1-rpi-v6", "binary_version": "1:6.1.21-1+rpt1" }, { "binary_name": "linux-image-6.1.0-rpi1-rpi-v7", "binary_version": "1:6.1.21-1+rpt1" }, { "binary_name": "linux-image-6.1.0-rpi1-rpi-v7l", "binary_version": "1:6.1.21-1+rpt1" }, { "binary_name": "linux-image-6.1.0-rpi1-rpi-v8", "binary_version": "1:6.1.21-1+rpt1" }, { "binary_name": "linux-image-6.1.0-rpi2-rpi-v6", "binary_version": "1:6.1.47-1+rpt2" }, { "binary_name": 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"https://git.kernel.org/stable/c/195b7bcdfc5adc5b2468f279dd9eb7eebd2e7632" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/fb61d7b9fb6ef0032de469499a54dab4c7260d0d" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/b180739b45a38b4caa88fe16bb5273072e6613dc" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/f8bd689f37f4198a4c61c4684f591ba639595b97" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/f0c18025693707ec344a70b6887f7450bf4c826b" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-08-05T11:52:36Z", "severity": { "source": "kernel CNA", "cvss_v3_score": 7.5, "cvss_v3_severity": "High", "scenario": "AV:N - The malformed zero-length sk_msg originates directly from a TCP FIN segment received from a remote peer over the network, and the crash occurs on the ordinary `recvmsg()` of a network-facing service whose sockets are managed by a BPF sockmap (e.g. service-mesh/L7 proxy socket acceleration). The oops trace is squarely in the TCP receive path (`__sys_recvfrom` \u2192 `inet_recvmsg` \u2192 `tcp_bpf_recvmsg_parser` \u2192 `sk_msg_recvmsg`).\nAC:L - The remote peer simply completes a TCP handshake and half-closes the connection; `tcp_bpf_recvmsg_parser()` itself notes this FIN path is \"the typical case\", and the commit states the crash \"happens every time\" in the reproducer. No race, no memory-layout grooming, and the attacker fully controls the FIN.\nPR:N - No credentials or prior authentication are needed \u2014 any client able to open a TCP connection to the sockmap-enrolled service can send the FIN. The CAP_NET_ADMIN/CAP_BPF needed to install the sockmap belongs to the victim's own configuration, not to the attacker.\nUI:N - The FIN makes the socket readable (EPOLLIN) and the server's normal epoll/recv loop consumes it automatically, triggering the dereference with no action by any local user.\nS:U - The fault and its consequences are confined to the kernel of the affected host; no VM, IOMMU, or other security-authority boundary is crossed.\nC:N - `copy` is zero, so `_copy_to_iter()` transfers no bytes and no kernel memory is exposed to userspace; the defect is purely a NULL `struct page` pointer being dereferenced by `page_address()`/`PageHighMem()`.\nI:N - There is no write primitive \u2014 the code path only reads `struct page` fields at a NULL base and copies zero bytes, so no kernel or user data can be modified.\nA:H - The NULL pointer dereference produces a kernel Oops and \"Kernel panic - not syncing: Fatal exception\", and because it fires on every graceful close it can be triggered repeatedly and trivially by any remote client." } } }