From: Daniel Borkmann <daniel@iogearbox.net> mainline inclusion from mainline-v7.1-rc1 commit ee861486e377edc55361c08dcbceab3f6b6577bd category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/15793 CVE: CVE-2026-53090 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- Usage of ld_{abs,ind} instructions got extended into subprogs some time ago via commit 09b28d76eac4 ("bpf: Add abnormal return checks."). These are only allowed in subprograms when the latter are BTF annotated and have scalar return types. The code generator in bpf_gen_ld_abs() has an abnormal exit path (r0=0 + exit) from legacy cBPF times. While the enforcement is on scalar return types, the verifier must also simulate the path of abnormal exit if the packet data load via ld_{abs,ind} failed. This is currently not the case. Fix it by having the verifier simulate both success and failure paths, and extend it in similar ways as we do for tail calls. The success path (r0=unknown, continue to next insn) is pushed onto stack for later validation and the r0=0 and return to the caller is done on the fall-through side. Fixes: 09b28d76eac4 ("bpf: Add abnormal return checks.") Reported-by: STAR Labs SG <info@starlabs.sg> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://lore.kernel.org/r/20260408191242.526279-2-daniel@iogearbox.net Signed-off-by: Alexei Starovoitov <ast@kernel.org> Conflicts: kernel/bpf/verifier.c [The current version does not introduce consumers corresponding to the output of jump tables; therefore, the assignment of jump tables is not involved. And mark_reg_scratched is for logging, so no need to backport it.] Signed-off-by: Pu Lehui <pulehui@huawei.com> --- kernel/bpf/verifier.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index edeff06b04d4..ad90fe6224db 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -8769,6 +8769,22 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn) mark_reg_unknown(env, regs, BPF_REG_0); /* ld_abs load up to 32-bit skb data. */ regs[BPF_REG_0].subreg_def = env->insn_idx + 1; + /* + * See bpf_gen_ld_abs() which emits a hidden BPF_EXIT with r0=0 + * which must be explored by the verifier when in a subprog. + */ + if (env->cur_state->curframe) { + struct bpf_verifier_state *branch; + + branch = push_stack(env, env->insn_idx + 1, env->insn_idx, false); + if (IS_ERR(branch)) + return PTR_ERR(branch); + mark_reg_known_zero(env, regs, BPF_REG_0); + err = prepare_func_exit(env, &env->insn_idx); + if (err) + return err; + env->insn_idx--; + } return 0; } -- 2.34.1