From: Chengkaitao <[email protected]> For the following scenario: struct tree_node { struct bpf_rb_node node; struct request __kptr *req; u64 key; }; struct bpf_rb_root tree_root __contains(tree_node, node); struct bpf_spin_lock tree_lock;
If we need to traverse all nodes in the rbtree, retrieve the __kptr pointer from each node, and read kernel data from the referenced object, using bpf_kptr_xchg appears unavoidable. This patch skips the BPF verifier checks for bpf_kptr_xchg when called while holding a lock. Signed-off-by: Chengkaitao <[email protected]> --- kernel/bpf/verifier.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 3135643d5695..05a6a6606b6c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -20387,7 +20387,8 @@ static int do_check_insn(struct bpf_verifier_env *env, bool *do_print_state) if (env->cur_state->active_locks) { if ((insn->src_reg == BPF_REG_0 && - insn->imm != BPF_FUNC_spin_unlock) || + insn->imm != BPF_FUNC_spin_unlock && + insn->imm != BPF_FUNC_kptr_xchg) || (insn->src_reg == BPF_PSEUDO_KFUNC_CALL && (insn->off != 0 || !kfunc_spin_allowed(insn->imm)))) { verbose(env, -- 2.50.1 (Apple Git-155)
