Description
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.
Affected products
Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.
Linux Linux
Default version status: unaffected
5e43f899b03a3492ce5fc44e8900becb04dae9c0 to < e53a59e7cee5c1605d1ed595933098c2b69108f9affected5e43f899b03a3492ce5fc44e8900becb04dae9c0 to < dc4f348952173beb8ceb15be30b249276eccb605affected5e43f899b03a3492ce5fc44e8900becb04dae9c0 to < a99de19128aec0913f3d529f529fbbff5edfaff8affected5e43f899b03a3492ce5fc44e8900becb04dae9c0 to < 08cb3dc9d2b44f153d0bcf2cb966e4a94b5d0f32affected5e43f899b03a3492ce5fc44e8900becb04dae9c0 to < f856c598080ba7ce1252867b8ecd6ad5bdaf9a6aaffected5e43f899b03a3492ce5fc44e8900becb04dae9c0 to < c1ad19b5d8e23123503dcaf2d4342e1b90b923adaffected5e43f899b03a3492ce5fc44e8900becb04dae9c0 to < 4540aed51b12bc13364149bf95f6ecef013197c0affected
Linux Linux
Default version status: affected
4.17affected0 to < 4.17unaffected5.10.270 to ≤ 5.10.*unaffected5.15.221 to ≤ 5.15.*unaffected6.1.156 to ≤ 6.1.*unaffected6.6.112 to ≤ 6.6.*unaffected6.12.53 to ≤ 6.12.*unaffected6.17.3 to ≤ 6.17.*unaffected6.18 to ≤ *unaffected
References
- https://git.kernel.org/stable/c/e53a59e7cee5c1605d1ed595933098c2b69108f9 ↗
- https://git.kernel.org/stable/c/dc4f348952173beb8ceb15be30b249276eccb605 ↗
- https://git.kernel.org/stable/c/a99de19128aec0913f3d529f529fbbff5edfaff8 ↗
- https://git.kernel.org/stable/c/08cb3dc9d2b44f153d0bcf2cb966e4a94b5d0f32 ↗
- https://git.kernel.org/stable/c/f856c598080ba7ce1252867b8ecd6ad5bdaf9a6a ↗
- https://git.kernel.org/stable/c/c1ad19b5d8e23123503dcaf2d4342e1b90b923ad ↗
- https://git.kernel.org/stable/c/4540aed51b12bc13364149bf95f6ecef013197c0 ↗