From: Youlin Li Date: Thu, 3 Nov 2022 09:34:39 +0000 (+0800) Subject: bpf: Fix wrong reg type conversion in release_reference() X-Git-Tag: v6.1-rc5~24^2~50^2~1 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=f1db20814af532f85e091231223e5e4818e8464b;p=platform%2Fkernel%2Flinux-starfive.git bpf: Fix wrong reg type conversion in release_reference() Some helper functions will allocate memory. To avoid memory leaks, the verifier requires the eBPF program to release these memories by calling the corresponding helper functions. When a resource is released, all pointer registers corresponding to the resource should be invalidated. The verifier use release_references() to do this job, by apply __mark_reg_unknown() to each relevant register. It will give these registers the type of SCALAR_VALUE. A register that will contain a pointer value at runtime, but of type SCALAR_VALUE, which may allow the unprivileged user to get a kernel pointer by storing this register into a map. Using __mark_reg_not_init() while NOT allow_ptr_leaks can mitigate this problem. Fixes: fd978bf7fd31 ("bpf: Add reference tracking to verifier") Signed-off-by: Youlin Li Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20221103093440.3161-1-liulin063@gmail.com --- diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index dd9019c..2256663 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -6623,8 +6623,12 @@ static int release_reference(struct bpf_verifier_env *env, return err; bpf_for_each_reg_in_vstate(env->cur_state, state, reg, ({ - if (reg->ref_obj_id == ref_obj_id) - __mark_reg_unknown(env, reg); + if (reg->ref_obj_id == ref_obj_id) { + if (!env->allow_ptr_leaks) + __mark_reg_not_init(env, reg); + else + __mark_reg_unknown(env, reg); + } })); return 0;