| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2023-52523: bpf, sockmap: Reject sk_msg egress redirects to non-TCP sockets |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| bpf, sockmap: Reject sk_msg egress redirects to non-TCP sockets |
| |
| With a SOCKMAP/SOCKHASH map and an sk_msg program user can steer messages |
| sent from one TCP socket (s1) to actually egress from another TCP |
| socket (s2): |
| |
| tcp_bpf_sendmsg(s1) // = sk_prot->sendmsg |
| tcp_bpf_send_verdict(s1) // __SK_REDIRECT case |
| tcp_bpf_sendmsg_redir(s2) |
| tcp_bpf_push_locked(s2) |
| tcp_bpf_push(s2) |
| tcp_rate_check_app_limited(s2) // expects tcp_sock |
| tcp_sendmsg_locked(s2) // ditto |
| |
| There is a hard-coded assumption in the call-chain, that the egress |
| socket (s2) is a TCP socket. |
| |
| However in commit 122e6c79efe1 ("sock_map: Update sock type checks for |
| UDP") we have enabled redirects to non-TCP sockets. This was done for the |
| sake of BPF sk_skb programs. There was no indention to support sk_msg |
| send-to-egress use case. |
| |
| As a result, attempts to send-to-egress through a non-TCP socket lead to a |
| crash due to invalid downcast from sock to tcp_sock: |
| |
| BUG: kernel NULL pointer dereference, address: 000000000000002f |
| ... |
| Call Trace: |
| <TASK> |
| ? show_regs+0x60/0x70 |
| ? __die+0x1f/0x70 |
| ? page_fault_oops+0x80/0x160 |
| ? do_user_addr_fault+0x2d7/0x800 |
| ? rcu_is_watching+0x11/0x50 |
| ? exc_page_fault+0x70/0x1c0 |
| ? asm_exc_page_fault+0x27/0x30 |
| ? tcp_tso_segs+0x14/0xa0 |
| tcp_write_xmit+0x67/0xce0 |
| __tcp_push_pending_frames+0x32/0xf0 |
| tcp_push+0x107/0x140 |
| tcp_sendmsg_locked+0x99f/0xbb0 |
| tcp_bpf_push+0x19d/0x3a0 |
| tcp_bpf_sendmsg_redir+0x55/0xd0 |
| tcp_bpf_send_verdict+0x407/0x550 |
| tcp_bpf_sendmsg+0x1a1/0x390 |
| inet_sendmsg+0x6a/0x70 |
| sock_sendmsg+0x9d/0xc0 |
| ? sockfd_lookup_light+0x12/0x80 |
| __sys_sendto+0x10e/0x160 |
| ? syscall_enter_from_user_mode+0x20/0x60 |
| ? __this_cpu_preempt_check+0x13/0x20 |
| ? lockdep_hardirqs_on+0x82/0x110 |
| __x64_sys_sendto+0x1f/0x30 |
| do_syscall_64+0x38/0x90 |
| entry_SYSCALL_64_after_hwframe+0x63/0xcd |
| |
| Reject selecting a non-TCP sockets as redirect target from a BPF sk_msg |
| program to prevent the crash. When attempted, user will receive an EACCES |
| error from send/sendto/sendmsg() syscall. |
| |
| The Linux kernel CVE team has assigned CVE-2023-52523 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.13 with commit 122e6c79efe1c25816118aca9cfabe54e99c2432 and fixed in 5.15.135 with commit bc8b89b6963803a123f64aa9494155a037b3d728 |
| Issue introduced in 5.13 with commit 122e6c79efe1c25816118aca9cfabe54e99c2432 and fixed in 6.1.57 with commit b8f97e47b6fb84fcf2f5a22e725eefb6cf5070c2 |
| Issue introduced in 5.13 with commit 122e6c79efe1c25816118aca9cfabe54e99c2432 and fixed in 6.5.7 with commit ded6e448028f0f91b6af35985afca01fa02a9089 |
| Issue introduced in 5.13 with commit 122e6c79efe1c25816118aca9cfabe54e99c2432 and fixed in 6.6 with commit b80e31baa43614e086a9d29dc1151932b1bd7fc5 |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2023-52523 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| net/core/sock_map.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/bc8b89b6963803a123f64aa9494155a037b3d728 |
| https://git.kernel.org/stable/c/b8f97e47b6fb84fcf2f5a22e725eefb6cf5070c2 |
| https://git.kernel.org/stable/c/ded6e448028f0f91b6af35985afca01fa02a9089 |
| https://git.kernel.org/stable/c/b80e31baa43614e086a9d29dc1151932b1bd7fc5 |
