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bpf: Fix net.core.bpf_jit_harden race

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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 <houtao1@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220309123321.2400262-4-houtao1@huawei.com
This commit is contained in:
Hou Tao 2022-03-09 20:33:20 +08:00 committed by Alexei Starovoitov
parent 73e14451f3
commit d2a3b7c5be
3 changed files with 6 additions and 3 deletions
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1
include/linux/filter.h
View File

@ -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? */

3
kernel/bpf/core.c
View File

@ -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);

5
kernel/bpf/verifier.c
View File

@ -13023,6 +13023,7 @@ 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;
@ -13146,6 +13147,7 @@ out_free:
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;
@ -13239,7 +13241,6 @@ 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;
@ -13403,7 +13404,7 @@ 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) &&