From: Eduard Zingerman <eddyz87@gmail.com> stable inclusion from stable-v6.6.158 commit 8cb75f7ada25b1cf25f2f74dec3ba649b9064a09 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/19759 CVE: CVE-2026-98075 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit 374b2c5561db80fcdd7cdce44af37a49416f61c7 ] fixups.c:jit_subprogs() rewrites BPF_PSEUDO_FUNC loads to contain real function addresses. This function is invoked from bpf_jit_subprogs() only when env->subprog_cnt > 1. Meaning that for any program like below: int main(void *ctx) { void *ptr = main; ... bpf_timer_set_callback(..., ptr); ... } The 'ptr' won't be ever converted to contain an address. In combination with e.g. bpf_timer_set_callback() this would lead to a function call at a bogus address. Instead of complicating the implementation, just assume that no useful program needs main to be a sync or async callback and reject BPF_PSEUDO_FUNC loads for the main subprogram. Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper") Reported-by: Nicholas Carlini <npc@anthropic.com> Suggested-by: Nicholas Carlini <npc@anthropic.com> Signed-off-by: Eduard Zingerman <eddyz87@gmail.com> Link: https://lore.kernel.org/r/20260902233658.1186477-1-eddyz87@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Pu Lehui <pulehui@huawei.com> --- kernel/bpf/verifier.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index c9921971950d..b796d985e420 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -15286,6 +15286,15 @@ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn) verbose(env, "callback function not static\n"); return -EINVAL; } + /* + * When env->subprog_cnt == 1 this instruction won't be rewritten + * to hold a real function address. Assume that no usable program + * combines e.g. main and timer callback and just reject here. + */ + if (subprogno == 0) { + verbose(env, "callback function cannot be the main program\n"); + return -EINVAL; + } dst_reg->type = PTR_TO_FUNC; dst_reg->subprogno = subprogno; -- 2.34.1