diff options
Diffstat (limited to 'kernel/bpf/core.c')
-rw-r--r-- | kernel/bpf/core.c | 308 |
1 files changed, 301 insertions, 7 deletions
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index be0abf6..b94a365 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -129,14 +129,83 @@ struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size, return fp; } -EXPORT_SYMBOL_GPL(bpf_prog_realloc); void __bpf_prog_free(struct bpf_prog *fp) { kfree(fp->aux); vfree(fp); } -EXPORT_SYMBOL_GPL(__bpf_prog_free); + +static bool bpf_is_jmp_and_has_target(const struct bpf_insn *insn) +{ + return BPF_CLASS(insn->code) == BPF_JMP && + /* Call and Exit are both special jumps with no + * target inside the BPF instruction image. + */ + BPF_OP(insn->code) != BPF_CALL && + BPF_OP(insn->code) != BPF_EXIT; +} + +static void bpf_adj_branches(struct bpf_prog *prog, u32 pos, u32 delta) +{ + struct bpf_insn *insn = prog->insnsi; + u32 i, insn_cnt = prog->len; + + for (i = 0; i < insn_cnt; i++, insn++) { + if (!bpf_is_jmp_and_has_target(insn)) + continue; + + /* Adjust offset of jmps if we cross boundaries. */ + if (i < pos && i + insn->off + 1 > pos) + insn->off += delta; + else if (i > pos + delta && i + insn->off + 1 <= pos + delta) + insn->off -= delta; + } +} + +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; + struct bpf_prog *prog_adj; + + /* Since our patchlet doesn't expand the image, we're done. */ + if (insn_delta == 0) { + memcpy(prog->insnsi + off, patch, sizeof(*patch)); + return prog; + } + + insn_adj_cnt = prog->len + insn_delta; + + /* 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. + */ + prog_adj = bpf_prog_realloc(prog, bpf_prog_size(insn_adj_cnt), + GFP_USER); + if (!prog_adj) + return NULL; + + prog_adj->len = insn_adj_cnt; + + /* Patching happens in 3 steps: + * + * 1) Move over tail of insnsi from next instruction onwards, + * so we can patch the single target insn with one or more + * new ones (patching is always from 1 to n insns, n > 0). + * 2) Inject new instructions at the target location. + * 3) Adjust branch offsets if necessary. + */ + insn_rest = insn_adj_cnt - off - len; + + memmove(prog_adj->insnsi + off + len, prog_adj->insnsi + off + 1, + sizeof(*patch) * insn_rest); + memcpy(prog_adj->insnsi + off, patch, sizeof(*patch) * len); + + bpf_adj_branches(prog_adj, off, insn_delta); + + return prog_adj; +} #ifdef CONFIG_BPF_JIT struct bpf_binary_header * @@ -162,7 +231,7 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr, hdr->pages = size / PAGE_SIZE; hole = min_t(unsigned int, size - (proglen + sizeof(*hdr)), PAGE_SIZE - sizeof(*hdr)); - start = (prandom_u32() % hole) & ~(alignment - 1); + start = (get_random_int() % hole) & ~(alignment - 1); /* Leave a random number of instructions before BPF code. */ *image_ptr = &hdr->image[start]; @@ -174,6 +243,209 @@ void bpf_jit_binary_free(struct bpf_binary_header *hdr) { module_memfree(hdr); } + +int bpf_jit_harden __read_mostly; + +static int bpf_jit_blind_insn(const struct bpf_insn *from, + const struct bpf_insn *aux, + struct bpf_insn *to_buff) +{ + struct bpf_insn *to = to_buff; + u32 imm_rnd = get_random_int(); + s16 off; + + BUILD_BUG_ON(BPF_REG_AX + 1 != MAX_BPF_JIT_REG); + BUILD_BUG_ON(MAX_BPF_REG + 1 != MAX_BPF_JIT_REG); + + if (from->imm == 0 && + (from->code == (BPF_ALU | BPF_MOV | BPF_K) || + from->code == (BPF_ALU64 | BPF_MOV | BPF_K))) { + *to++ = BPF_ALU64_REG(BPF_XOR, from->dst_reg, from->dst_reg); + goto out; + } + + switch (from->code) { + case BPF_ALU | BPF_ADD | BPF_K: + case BPF_ALU | BPF_SUB | BPF_K: + case BPF_ALU | BPF_AND | BPF_K: + case BPF_ALU | BPF_OR | BPF_K: + case BPF_ALU | BPF_XOR | BPF_K: + case BPF_ALU | BPF_MUL | BPF_K: + case BPF_ALU | BPF_MOV | BPF_K: + case BPF_ALU | BPF_DIV | BPF_K: + case BPF_ALU | BPF_MOD | BPF_K: + *to++ = BPF_ALU32_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ from->imm); + *to++ = BPF_ALU32_IMM(BPF_XOR, BPF_REG_AX, imm_rnd); + *to++ = BPF_ALU32_REG(from->code, from->dst_reg, BPF_REG_AX); + break; + + case BPF_ALU64 | BPF_ADD | BPF_K: + case BPF_ALU64 | BPF_SUB | BPF_K: + case BPF_ALU64 | BPF_AND | BPF_K: + case BPF_ALU64 | BPF_OR | BPF_K: + case BPF_ALU64 | BPF_XOR | BPF_K: + case BPF_ALU64 | BPF_MUL | BPF_K: + case BPF_ALU64 | BPF_MOV | BPF_K: + case BPF_ALU64 | BPF_DIV | BPF_K: + case BPF_ALU64 | BPF_MOD | BPF_K: + *to++ = BPF_ALU64_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ from->imm); + *to++ = BPF_ALU64_IMM(BPF_XOR, BPF_REG_AX, imm_rnd); + *to++ = BPF_ALU64_REG(from->code, from->dst_reg, BPF_REG_AX); + break; + + case BPF_JMP | BPF_JEQ | BPF_K: + case BPF_JMP | BPF_JNE | BPF_K: + case BPF_JMP | BPF_JGT | BPF_K: + case BPF_JMP | BPF_JGE | BPF_K: + case BPF_JMP | BPF_JSGT | BPF_K: + case BPF_JMP | BPF_JSGE | BPF_K: + case BPF_JMP | BPF_JSET | BPF_K: + /* Accommodate for extra offset in case of a backjump. */ + off = from->off; + if (off < 0) + off -= 2; + *to++ = BPF_ALU64_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ from->imm); + *to++ = BPF_ALU64_IMM(BPF_XOR, BPF_REG_AX, imm_rnd); + *to++ = BPF_JMP_REG(from->code, from->dst_reg, BPF_REG_AX, off); + break; + + case BPF_LD | BPF_ABS | BPF_W: + case BPF_LD | BPF_ABS | BPF_H: + case BPF_LD | BPF_ABS | BPF_B: + *to++ = BPF_ALU64_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ from->imm); + *to++ = BPF_ALU64_IMM(BPF_XOR, BPF_REG_AX, imm_rnd); + *to++ = BPF_LD_IND(from->code, BPF_REG_AX, 0); + break; + + case BPF_LD | BPF_IND | BPF_W: + case BPF_LD | BPF_IND | BPF_H: + case BPF_LD | BPF_IND | BPF_B: + *to++ = BPF_ALU64_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ from->imm); + *to++ = BPF_ALU64_IMM(BPF_XOR, BPF_REG_AX, imm_rnd); + *to++ = BPF_ALU32_REG(BPF_ADD, BPF_REG_AX, from->src_reg); + *to++ = BPF_LD_IND(from->code, BPF_REG_AX, 0); + break; + + case BPF_LD | BPF_IMM | BPF_DW: + *to++ = BPF_ALU64_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ aux[1].imm); + *to++ = BPF_ALU64_IMM(BPF_XOR, BPF_REG_AX, imm_rnd); + *to++ = BPF_ALU64_IMM(BPF_LSH, BPF_REG_AX, 32); + *to++ = BPF_ALU64_REG(BPF_MOV, aux[0].dst_reg, BPF_REG_AX); + break; + case 0: /* Part 2 of BPF_LD | BPF_IMM | BPF_DW. */ + *to++ = BPF_ALU32_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ aux[0].imm); + *to++ = BPF_ALU32_IMM(BPF_XOR, BPF_REG_AX, imm_rnd); + *to++ = BPF_ALU64_REG(BPF_OR, aux[0].dst_reg, BPF_REG_AX); + break; + + case BPF_ST | BPF_MEM | BPF_DW: + case BPF_ST | BPF_MEM | BPF_W: + case BPF_ST | BPF_MEM | BPF_H: + case BPF_ST | BPF_MEM | BPF_B: + *to++ = BPF_ALU64_IMM(BPF_MOV, BPF_REG_AX, imm_rnd ^ from->imm); + *to++ = BPF_ALU64_IMM(BPF_XOR, BPF_REG_AX, imm_rnd); + *to++ = BPF_STX_MEM(from->code, from->dst_reg, BPF_REG_AX, from->off); + break; + } +out: + return to - to_buff; +} + +static struct bpf_prog *bpf_prog_clone_create(struct bpf_prog *fp_other, + gfp_t gfp_extra_flags) +{ + gfp_t gfp_flags = GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO | + gfp_extra_flags; + struct bpf_prog *fp; + + fp = __vmalloc(fp_other->pages * PAGE_SIZE, gfp_flags, PAGE_KERNEL); + if (fp != NULL) { + kmemcheck_annotate_bitfield(fp, meta); + + /* aux->prog still points to the fp_other one, so + * when promoting the clone to the real program, + * this still needs to be adapted. + */ + memcpy(fp, fp_other, fp_other->pages * PAGE_SIZE); + } + + return fp; +} + +static void bpf_prog_clone_free(struct bpf_prog *fp) +{ + /* aux was stolen by the other clone, so we cannot free + * it from this path! It will be freed eventually by the + * other program on release. + * + * At this point, we don't need a deferred release since + * clone is guaranteed to not be locked. + */ + fp->aux = NULL; + __bpf_prog_free(fp); +} + +void bpf_jit_prog_release_other(struct bpf_prog *fp, struct bpf_prog *fp_other) +{ + /* We have to repoint aux->prog to self, as we don't + * know whether fp here is the clone or the original. + */ + fp->aux->prog = fp; + bpf_prog_clone_free(fp_other); +} + +struct bpf_prog *bpf_jit_blind_constants(struct bpf_prog *prog) +{ + struct bpf_insn insn_buff[16], aux[2]; + struct bpf_prog *clone, *tmp; + int insn_delta, insn_cnt; + struct bpf_insn *insn; + int i, rewritten; + + if (!bpf_jit_blinding_enabled()) + return prog; + + clone = bpf_prog_clone_create(prog, GFP_USER); + if (!clone) + return ERR_PTR(-ENOMEM); + + insn_cnt = clone->len; + insn = clone->insnsi; + + for (i = 0; i < insn_cnt; i++, insn++) { + /* We temporarily need to hold the original ld64 insn + * so that we can still access the first part in the + * second blinding run. + */ + if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW) && + insn[1].code == 0) + memcpy(aux, insn, sizeof(aux)); + + rewritten = bpf_jit_blind_insn(insn, aux, insn_buff); + if (!rewritten) + continue; + + tmp = bpf_patch_insn_single(clone, i, insn_buff, rewritten); + if (!tmp) { + /* Patching may have repointed aux->prog during + * realloc from the original one, so we need to + * fix it up here on error. + */ + bpf_jit_prog_release_other(prog, clone); + return ERR_PTR(-ENOMEM); + } + + clone = tmp; + insn_delta = rewritten - 1; + + /* Walk new program and skip insns we just inserted. */ + insn = clone->insnsi + i + insn_delta; + insn_cnt += insn_delta; + i += insn_delta; + } + + return clone; +} #endif /* CONFIG_BPF_JIT */ /* Base function for offset calculation. Needs to go into .text section, @@ -692,15 +964,22 @@ static int bpf_check_tail_call(const struct bpf_prog *fp) /** * bpf_prog_select_runtime - select exec runtime for BPF program * @fp: bpf_prog populated with internal BPF program + * @err: pointer to error variable * * Try to JIT eBPF program, if JIT is not available, use interpreter. * The BPF program will be executed via BPF_PROG_RUN() macro. */ -int bpf_prog_select_runtime(struct bpf_prog *fp) +struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err) { fp->bpf_func = (void *) __bpf_prog_run; - bpf_int_jit_compile(fp); + /* eBPF JITs can rewrite the program in case constant + * blinding is active. However, in case of error during + * blinding, bpf_int_jit_compile() must always return a + * valid program, which in this case would simply not + * be JITed, but falls back to the interpreter. + */ + fp = bpf_int_jit_compile(fp); bpf_prog_lock_ro(fp); /* The tail call compatibility check can only be done at @@ -708,7 +987,9 @@ int bpf_prog_select_runtime(struct bpf_prog *fp) * with JITed or non JITed program concatenations and not * all eBPF JITs might immediately support all features. */ - return bpf_check_tail_call(fp); + *err = bpf_check_tail_call(fp); + + return fp; } EXPORT_SYMBOL_GPL(bpf_prog_select_runtime); @@ -764,14 +1045,21 @@ const struct bpf_func_proto bpf_map_delete_elem_proto __weak; const struct bpf_func_proto bpf_get_prandom_u32_proto __weak; const struct bpf_func_proto bpf_get_smp_processor_id_proto __weak; const struct bpf_func_proto bpf_ktime_get_ns_proto __weak; + const struct bpf_func_proto bpf_get_current_pid_tgid_proto __weak; const struct bpf_func_proto bpf_get_current_uid_gid_proto __weak; const struct bpf_func_proto bpf_get_current_comm_proto __weak; + const struct bpf_func_proto * __weak bpf_get_trace_printk_proto(void) { return NULL; } +const struct bpf_func_proto * __weak bpf_get_event_output_proto(void) +{ + return NULL; +} + /* Always built-in helper functions. */ const struct bpf_func_proto bpf_tail_call_proto = { .func = NULL, @@ -783,8 +1071,14 @@ const struct bpf_func_proto bpf_tail_call_proto = { }; /* For classic BPF JITs that don't implement bpf_int_jit_compile(). */ -void __weak bpf_int_jit_compile(struct bpf_prog *prog) +struct bpf_prog * __weak bpf_int_jit_compile(struct bpf_prog *prog) +{ + return prog; +} + +bool __weak bpf_helper_changes_skb_data(void *func) { + return false; } /* To execute LD_ABS/LD_IND instructions __bpf_prog_run() may call |