CVE-2025-38591

Description

In the Linux kernel, the following vulnerability has been resolved:bpf: Reject narrower access to pointer ctx fieldsThe following BPF program, simplified from a syzkaller repro, causes akernel warning: r0 = *(u8 *)(r1 + 169); exit;With pointer field sk being at offset 168 in __sk_buff. This access isdetected as a narrower read in bpf_skb_is_valid_access because itdoesnt match offsetof(struct __sk_buff, sk). It is therefore allowedand later proceeds to bpf_convert_ctx_access. Note that for theis_narrower_load case in the convert_ctx_accesses(), the insn->offis aligned, so the cnt may not be 0 because it matches theoffsetof(struct __sk_buff, sk) in the bpf_convert_ctx_access. However,the target_size stays 0 and the verifier errors with a kernel warning: verifier bug: error during ctx access conversion(1)This patch fixes that to return a proper invalid bpf_context accessoff=X size=Y error on the load instruction.The same issue affects multiple other fields in context structures thatallow narrow access. Some other non-affected fields (for sk_msg,sk_lookup, and sockopt) were also changed to use bpf_ctx_range_ptr forconsistency.Note this syzkaller crash was reported in the Closes link below, whichused to be about a different bug, fixed incommit fce7bd8e385a (bpf/verifier: Handle BPF_LOAD_ACQ instructionsin insn_def_regno()). Because syzbot somehow confused the two bugs,the new crash and repro didnt get reported to the mailing list.

Risk Information

Associated Vulnerability

Patch Details

References

https://nvd.nist.gov/vuln/detail/CVE-2023-1234
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-1234