diff options
Diffstat (limited to 'kernel/bpf/core.c')
-rw-r--r-- | kernel/bpf/core.c | 145 |
1 files changed, 104 insertions, 41 deletions
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index d315b393abdd..6ef6746a7871 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -218,47 +218,84 @@ int bpf_prog_calc_tag(struct bpf_prog *fp) return 0; } -static void bpf_adj_branches(struct bpf_prog *prog, u32 pos, u32 delta) +static int bpf_adj_delta_to_imm(struct bpf_insn *insn, u32 pos, u32 delta, + u32 curr, const bool probe_pass) { + const s64 imm_min = S32_MIN, imm_max = S32_MAX; + s64 imm = insn->imm; + + if (curr < pos && curr + imm + 1 > pos) + imm += delta; + else if (curr > pos + delta && curr + imm + 1 <= pos + delta) + imm -= delta; + if (imm < imm_min || imm > imm_max) + return -ERANGE; + if (!probe_pass) + insn->imm = imm; + return 0; +} + +static int bpf_adj_delta_to_off(struct bpf_insn *insn, u32 pos, u32 delta, + u32 curr, const bool probe_pass) +{ + const s32 off_min = S16_MIN, off_max = S16_MAX; + s32 off = insn->off; + + if (curr < pos && curr + off + 1 > pos) + off += delta; + else if (curr > pos + delta && curr + off + 1 <= pos + delta) + off -= delta; + if (off < off_min || off > off_max) + return -ERANGE; + if (!probe_pass) + insn->off = off; + return 0; +} + +static int bpf_adj_branches(struct bpf_prog *prog, u32 pos, u32 delta, + const bool probe_pass) +{ + u32 i, insn_cnt = prog->len + (probe_pass ? delta : 0); struct bpf_insn *insn = prog->insnsi; - u32 i, insn_cnt = prog->len; - bool pseudo_call; - u8 code; - int off; + int ret = 0; for (i = 0; i < insn_cnt; i++, insn++) { + u8 code; + + /* In the probing pass we still operate on the original, + * unpatched image in order to check overflows before we + * do any other adjustments. Therefore skip the patchlet. + */ + if (probe_pass && i == pos) { + i += delta + 1; + insn++; + } code = insn->code; - if (BPF_CLASS(code) != BPF_JMP) - continue; - if (BPF_OP(code) == BPF_EXIT) + if (BPF_CLASS(code) != BPF_JMP || + BPF_OP(code) == BPF_EXIT) continue; + /* Adjust offset of jmps if we cross patch boundaries. */ if (BPF_OP(code) == BPF_CALL) { - if (insn->src_reg == BPF_PSEUDO_CALL) - pseudo_call = true; - else + if (insn->src_reg != BPF_PSEUDO_CALL) continue; + ret = bpf_adj_delta_to_imm(insn, pos, delta, i, + probe_pass); } else { - pseudo_call = false; + ret = bpf_adj_delta_to_off(insn, pos, delta, i, + probe_pass); } - off = pseudo_call ? insn->imm : insn->off; - - /* Adjust offset of jmps if we cross boundaries. */ - if (i < pos && i + off + 1 > pos) - off += delta; - else if (i > pos + delta && i + off + 1 <= pos + delta) - off -= delta; - - if (pseudo_call) - insn->imm = off; - else - insn->off = off; + if (ret) + break; } + + return ret; } struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off, const struct bpf_insn *patch, u32 len) { u32 insn_adj_cnt, insn_rest, insn_delta = len - 1; + const u32 cnt_max = S16_MAX; struct bpf_prog *prog_adj; /* Since our patchlet doesn't expand the image, we're done. */ @@ -269,6 +306,15 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off, insn_adj_cnt = prog->len + insn_delta; + /* Reject anything that would potentially let the insn->off + * target overflow when we have excessive program expansions. + * We need to probe here before we do any reallocation where + * we afterwards may not fail anymore. + */ + if (insn_adj_cnt > cnt_max && + bpf_adj_branches(prog, off, insn_delta, true)) + return NULL; + /* Several new instructions need to be inserted. Make room * for them. Likely, there's no need for a new allocation as * last page could have large enough tailroom. @@ -294,7 +340,11 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off, sizeof(*patch) * insn_rest); memcpy(prog_adj->insnsi + off, patch, sizeof(*patch) * len); - bpf_adj_branches(prog_adj, off, insn_delta); + /* We are guaranteed to not fail at this point, otherwise + * the ship has sailed to reverse to the original state. An + * overflow cannot happen at this point. + */ + BUG_ON(bpf_adj_branches(prog_adj, off, insn_delta, false)); return prog_adj; } @@ -1572,13 +1622,32 @@ int bpf_prog_array_length(struct bpf_prog_array __rcu *progs) return cnt; } +static bool bpf_prog_array_copy_core(struct bpf_prog **prog, + u32 *prog_ids, + u32 request_cnt) +{ + int i = 0; + + for (; *prog; prog++) { + if (*prog == &dummy_bpf_prog.prog) + continue; + prog_ids[i] = (*prog)->aux->id; + if (++i == request_cnt) { + prog++; + break; + } + } + + return !!(*prog); +} + int bpf_prog_array_copy_to_user(struct bpf_prog_array __rcu *progs, __u32 __user *prog_ids, u32 cnt) { struct bpf_prog **prog; unsigned long err = 0; - u32 i = 0, *ids; bool nospc; + u32 *ids; /* users of this function are doing: * cnt = bpf_prog_array_length(); @@ -1595,16 +1664,7 @@ int bpf_prog_array_copy_to_user(struct bpf_prog_array __rcu *progs, return -ENOMEM; rcu_read_lock(); prog = rcu_dereference(progs)->progs; - for (; *prog; prog++) { - if (*prog == &dummy_bpf_prog.prog) - continue; - ids[i] = (*prog)->aux->id; - if (++i == cnt) { - prog++; - break; - } - } - nospc = !!(*prog); + nospc = bpf_prog_array_copy_core(prog, ids, cnt); rcu_read_unlock(); err = copy_to_user(prog_ids, ids, cnt * sizeof(u32)); kfree(ids); @@ -1683,22 +1743,25 @@ int bpf_prog_array_copy(struct bpf_prog_array __rcu *old_array, } int bpf_prog_array_copy_info(struct bpf_prog_array __rcu *array, - __u32 __user *prog_ids, u32 request_cnt, - __u32 __user *prog_cnt) + u32 *prog_ids, u32 request_cnt, + u32 *prog_cnt) { + struct bpf_prog **prog; u32 cnt = 0; if (array) cnt = bpf_prog_array_length(array); - if (copy_to_user(prog_cnt, &cnt, sizeof(cnt))) - return -EFAULT; + *prog_cnt = cnt; /* return early if user requested only program count or nothing to copy */ if (!request_cnt || !cnt) return 0; - return bpf_prog_array_copy_to_user(array, prog_ids, request_cnt); + /* this function is called under trace/bpf_trace.c: bpf_event_mutex */ + prog = rcu_dereference_check(array, 1)->progs; + return bpf_prog_array_copy_core(prog, prog_ids, request_cnt) ? -ENOSPC + : 0; } static void bpf_prog_free_deferred(struct work_struct *work) |