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CVE-2025-40123

bpf: Enforce expected_attach_type for tailcall compatibility

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.270, 5.15.221, 6.1.156, 6.6.112, 6.12.53, and 1 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

Summary

In the Linux kernel, the following vulnerability has been resolved: bpf: Enforce expected_attach_type for tailcall compatibility Yinhao et al. recently reported: Our fuzzer tool discovered an uninitialized pointer issue in the bpf_prog_test_run_xdp() function within the Linux kernel's BPF subsystem. This leads to a NULL pointer dereference when a BPF program attempts to deference the txq member of struct xdp_buff object. The test initializes two programs of BPF_PROG_TYPE_XDP: progA acts as the entry point for bpf_prog_test_run_xdp() and its expected_attach_type can neither be of be BPF_XDP_DEVMAP nor BPF_XDP_CPUMAP. progA calls into a slot of a tailcall map it owns. progB's expected_attach_type must be BPF_XDP_DEVMAP to pass xdp_is_valid_access() validation. The program returns struct xdp_md's egress_ifindex, and the latter is only allowed to be accessed under mentioned expected_attach_type. progB is then inserted into the tailcall which progA calls. The underlying issue goes beyond XDP though. Another example are programs of type BPF_PROG_TYPE_CGROUP_SOCK_ADDR. sock_addr_is_valid_access() as well as sock_addr_func_proto() have different logic depending on the programs' expected_attach_type. Similarly, a program attached to BPF_CGROUP_INET4_GETPEERNAME should not be allowed doing a tailcall into a program which calls bpf_bind() out of BPF which is only enabled for BPF_CGROUP_INET4_CONNECT. In short, specifying expected_attach_type allows to open up additional functionality or restrictions beyond what the basic bpf_prog_type enables. The use of tailcalls must not violate these constraints. Fix it by enforcing expected_attach_type in __bpf_prog_map_compatible(). Note that we only enforce this for tailcall maps, but not for BPF devmaps or cpumaps: There, the programs are invoked through dev_map_bpf_prog_run*() and cpu_map_bpf_prog_run*() which set up a new environment / context and therefore these situations are not prone to this issue.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 5e43f899b03a3492ce5fc44e8900becb04dae9c0 · fixed in e53a59e7cee5c1605d1ed595933098c2b69108f9; From 5e43f899b03a3492ce5fc44e8900becb04dae9c0 · fixed in dc4f348952173beb8ceb15be30b249276eccb605; From 5e43f899b03a3492ce5fc44e8900becb04dae9c0 · fixed in a99de19128aec0913f3d529f529fbbff5edfaff8; From 5e43f899b03a3492ce5fc44e8900becb04dae9c0 · fixed in 08cb3dc9d2b44f153d0bcf2cb966e4a94b5d0f32; From 5e43f899b03a3492ce5fc44e8900becb04dae9c0 · fixed in f856c598080ba7ce1252867b8ecd6ad5bdaf9a6a; From 5e43f899b03a3492ce5fc44e8900becb04dae9c0 · fixed in c1ad19b5d8e23123503dcaf2d4342e1b90b923ad; From 5e43f899b03a3492ce5fc44e8900becb04dae9c0 · fixed in 4540aed51b12bc13364149bf95f6ecef013197c0

  • Linux Linux

    4.17

  • KernelLinux

    From 4.17.0 · fixed in 5.10.270; From 5.11.0 · fixed in 5.15.221; From 5.16.0 · fixed in 6.1.156; From 6.2.0 · fixed in 6.6.112; From 6.7.0 · fixed in 6.12.53; From 6.13.0 · fixed in 6.17.3

References 7

git.kernel.org