[PATCH bpf-next 3/4] bpf: Fix net.core.bpf_jit_harden race
From: Hou Tao <hidden>
Date: 2022-03-09 12:14:58
Also in:
bpf
Subsystem:
bpf [core], bpf [general] (safe dynamic programs and tools), the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
It is the bpf_jit_harden counterpart to commit 60b58afc96c9 ("bpf: fix
net.core.bpf_jit_enable race"). bpf_jit_harden will be tested twice
for each subprog if there are subprogs in bpf program and constant
blinding may increase the length of program, so when running
"./test_progs -t subprogs" and toggling bpf_jit_harden between 0 and 2,
jit_subprogs may fail because constant blinding increases the length
of subprog instructions during extra passs.
So cache the value of bpf_jit_blinding_enabled() during program
allocation, and use the cached value during constant blinding, subprog
JITing and args tracking of tail call.
Signed-off-by: Hou Tao <redacted>
---
include/linux/filter.h | 1 +
kernel/bpf/core.c | 3 ++-
kernel/bpf/verifier.c | 5 +++--
3 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index f3a913229edd..605c8456467b 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h@@ -566,6 +566,7 @@ struct bpf_prog { gpl_compatible:1, /* Is filter GPL compatible? */ cb_access:1, /* Is control block accessed? */ dst_needed:1, /* Do we need dst entry? */ + blinding_requested:1, /* needs constant blinding */ blinded:1, /* Was blinded */ is_func:1, /* program is a bpf function */ kprobe_override:1, /* Do we override a kprobe? */
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index a1841e11524c..a4b5fb095261 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c@@ -105,6 +105,7 @@ struct bpf_prog *bpf_prog_alloc_no_stats(unsigned int size, gfp_t gfp_extra_flag fp->aux = aux; fp->aux->prog = fp; fp->jit_requested = ebpf_jit_enabled(); + fp->blinding_requested = bpf_jit_blinding_enabled(fp); INIT_LIST_HEAD_RCU(&fp->aux->ksym.lnode); mutex_init(&fp->aux->used_maps_mutex);
@@ -1382,7 +1383,7 @@ struct bpf_prog *bpf_jit_blind_constants(struct bpf_prog *prog) struct bpf_insn *insn; int i, rewritten; - if (!bpf_jit_blinding_enabled(prog) || prog->blinded) + if (!prog->blinding_requested || prog->blinded) return prog; clone = bpf_prog_clone_create(prog, GFP_USER);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 885e515cf83f..ec4780bd44f1 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c@@ -13024,6 +13024,7 @@ static int jit_subprogs(struct bpf_verifier_env *env) func[i]->aux->name[0] = 'F'; func[i]->aux->stack_depth = env->subprog_info[i].stack_depth; func[i]->jit_requested = 1; + func[i]->blinding_requested = prog->blinding_requested; func[i]->aux->kfunc_tab = prog->aux->kfunc_tab; func[i]->aux->kfunc_btf_tab = prog->aux->kfunc_btf_tab; func[i]->aux->linfo = prog->aux->linfo;
@@ -13150,6 +13151,7 @@ static int jit_subprogs(struct bpf_verifier_env *env) out_undo_insn: /* cleanup main prog to be interpreted */ prog->jit_requested = 0; + prog->blinding_requested = 0; for (i = 0, insn = prog->insnsi; i < prog->len; i++, insn++) { if (!bpf_pseudo_call(insn)) continue;
@@ -13243,7 +13245,6 @@ static int do_misc_fixups(struct bpf_verifier_env *env) { struct bpf_prog *prog = env->prog; enum bpf_attach_type eatype = prog->expected_attach_type; - bool expect_blinding = bpf_jit_blinding_enabled(prog); enum bpf_prog_type prog_type = resolve_prog_type(prog); struct bpf_insn *insn = prog->insnsi; const struct bpf_func_proto *fn;
@@ -13407,7 +13408,7 @@ static int do_misc_fixups(struct bpf_verifier_env *env) insn->code = BPF_JMP | BPF_TAIL_CALL; aux = &env->insn_aux_data[i + delta]; - if (env->bpf_capable && !expect_blinding && + if (env->bpf_capable && !prog->blinding_requested && prog->jit_requested && !bpf_map_key_poisoned(aux) && !bpf_map_ptr_poisoned(aux) &&
--
2.29.2