From 8519ab031d8022999603a69ee9f18e8cfb06645d Mon Sep 17 00:00:00 2001 From: Thomas Haller Date: Tue, 12 Sep 2023 09:30:54 +0200 Subject: [PATCH] datatype: fix leak and cleanup reference counting for struct datatype Test `./tests/shell/run-tests.sh -V tests/shell/testcases/maps/nat_addr_port` fails: ==118== 195 (112 direct, 83 indirect) bytes in 1 blocks are definitely lost in loss record 3 of 3 ==118== at 0x484682C: calloc (vg_replace_malloc.c:1554) ==118== by 0x48A39DD: xmalloc (utils.c:37) ==118== by 0x48A39DD: xzalloc (utils.c:76) ==118== by 0x487BDFD: datatype_alloc (datatype.c:1205) ==118== by 0x487BDFD: concat_type_alloc (datatype.c:1288) ==118== by 0x488229D: stmt_evaluate_nat_map (evaluate.c:3786) ==118== by 0x488229D: stmt_evaluate_nat (evaluate.c:3892) ==118== by 0x488229D: stmt_evaluate (evaluate.c:4450) ==118== by 0x488328E: rule_evaluate (evaluate.c:4956) ==118== by 0x48ADC71: nft_evaluate (libnftables.c:552) ==118== by 0x48AEC29: nft_run_cmd_from_buffer (libnftables.c:595) ==118== by 0x402983: main (main.c:534) I think the reference handling for datatype is wrong. It was introduced by commit 01a13882bb59 ('src: add reference counter for dynamic datatypes'). We don't notice it most of the time, because instances are statically allocated, where datatype_get()/datatype_free() is a NOP. Fix and rework. - Commit 01a13882bb59 comments "The reference counter of any newly allocated datatype is set to zero". That seems not workable. Previously, functions like datatype_clone() would have returned the refcnt set to zero. Some callers would then then set the refcnt to one, but some wouldn't (set_datatype_alloc()). Calling datatype_free() with a refcnt of zero will overflow to UINT_MAX and leak: if (--dtype->refcnt > 0) return; While there could be schemes with such asymmetric counting that juggle the appropriate number of datatype_get() and datatype_free() calls, this is confusing and error prone. The common pattern is that every alloc/clone/get/ref is paired with exactly one unref/free. Let datatype_clone() return references with refcnt set 1 and in general be always clear about where we transfer ownership (take a reference) and where we need to release it. - set_datatype_alloc() needs to consistently return ownership to the reference. Previously, some code paths would and others wouldn't. - Replace datatype_set(key, set_datatype_alloc(dtype, key->byteorder)) with a __datatype_set() with takes ownership. Fixes: 01a13882bb59 ('src: add reference counter for dynamic datatypes') Signed-off-by: Thomas Haller Signed-off-by: Pablo Neira Ayuso --- include/datatype.h | 1 + include/expression.h | 4 +++ src/datatype.c | 23 ++++++++++---- src/evaluate.c | 47 ++++++++++++++++++++++++--------------- src/expression.c | 2 +- src/netlink.c | 31 +++++++++--------- src/netlink_delinearize.c | 2 +- 7 files changed, 70 insertions(+), 40 deletions(-) diff --git a/include/datatype.h b/include/datatype.h index 6146eda1..52a2e943 100644 --- a/include/datatype.h +++ b/include/datatype.h @@ -175,6 +175,7 @@ extern const struct datatype *datatype_lookup(enum datatypes type); extern const struct datatype *datatype_lookup_byname(const char *name); extern struct datatype *datatype_get(const struct datatype *dtype); extern void datatype_set(struct expr *expr, const struct datatype *dtype); +extern void __datatype_set(struct expr *expr, const struct datatype *dtype); extern void datatype_free(const struct datatype *dtype); struct parse_ctx { diff --git a/include/expression.h b/include/expression.h index 733dd3cf..469f41ec 100644 --- a/include/expression.h +++ b/include/expression.h @@ -116,7 +116,11 @@ enum symbol_types { * @maxval: expected maximum value */ struct expr_ctx { + /* expr_ctx does not own the reference to dtype. The caller must ensure + * the valid lifetime. + */ const struct datatype *dtype; + enum byteorder byteorder; unsigned int len; unsigned int maxval; diff --git a/src/datatype.c b/src/datatype.c index 678a16b1..70c84846 100644 --- a/src/datatype.c +++ b/src/datatype.c @@ -1078,6 +1078,7 @@ static struct datatype *dtype_alloc(void) dtype = xzalloc(sizeof(*dtype)); dtype->flags = DTYPE_F_ALLOC; + dtype->refcnt = 1; return dtype; } @@ -1095,12 +1096,19 @@ struct datatype *datatype_get(const struct datatype *ptr) return dtype; } +void __datatype_set(struct expr *expr, const struct datatype *dtype) +{ + const struct datatype *dtype_free; + + dtype_free = expr->dtype; + expr->dtype = dtype; + datatype_free(dtype_free); +} + void datatype_set(struct expr *expr, const struct datatype *dtype) { - if (dtype == expr->dtype) - return; - datatype_free(expr->dtype); - expr->dtype = datatype_get(dtype); + if (dtype != expr->dtype) + __datatype_set(expr, datatype_get(dtype)); } static struct datatype *dtype_clone(const struct datatype *orig_dtype) @@ -1112,7 +1120,7 @@ static struct datatype *dtype_clone(const struct datatype *orig_dtype) dtype->name = xstrdup(orig_dtype->name); dtype->desc = xstrdup(orig_dtype->desc); dtype->flags = DTYPE_F_ALLOC | orig_dtype->flags; - dtype->refcnt = 0; + dtype->refcnt = 1; return dtype; } @@ -1125,6 +1133,9 @@ void datatype_free(const struct datatype *ptr) return; if (!(dtype->flags & DTYPE_F_ALLOC)) return; + + assert(dtype->refcnt != 0); + if (--dtype->refcnt > 0) return; @@ -1177,7 +1188,7 @@ const struct datatype *set_datatype_alloc(const struct datatype *orig_dtype, /* Restrict dynamic datatype allocation to generic integer datatype. */ if (orig_dtype != &integer_type) - return orig_dtype; + return datatype_get(orig_dtype); dtype = dtype_clone(orig_dtype); dtype->byteorder = byteorder; diff --git a/src/evaluate.c b/src/evaluate.c index b0c6919f..1b7e0b37 100644 --- a/src/evaluate.c +++ b/src/evaluate.c @@ -74,7 +74,7 @@ static void key_fix_dtype_byteorder(struct expr *key) if (dtype->byteorder == key->byteorder) return; - datatype_set(key, set_datatype_alloc(dtype, key->byteorder)); + __datatype_set(key, set_datatype_alloc(dtype, key->byteorder)); } static int set_evaluate(struct eval_ctx *ctx, struct set *set); @@ -1289,7 +1289,7 @@ static int expr_evaluate_concat(struct eval_ctx *ctx, struct expr **expr) } (*expr)->flags |= flags; - datatype_set(*expr, concat_type_alloc(ntype)); + __datatype_set(*expr, concat_type_alloc(ntype)); (*expr)->len = (*expr)->dtype->size; if (off > 0) @@ -1519,7 +1519,6 @@ static int expr_evaluate_map(struct eval_ctx *ctx, struct expr **expr) { struct expr_ctx ectx = ctx->ectx; struct expr *map = *expr, *mappings; - const struct datatype *dtype; struct expr *key, *data; if (map->map->etype == EXPR_CT && @@ -1555,9 +1555,11 @@ static int expr_evaluate_map(struct eval_ctx *ctx, struct expr **expr) ctx->ectx.byteorder, ctx->ectx.len, NULL); + const struct datatype *dtype; dtype = set_datatype_alloc(ectx.dtype, ectx.byteorder); data = constant_expr_alloc(&netlink_location, dtype, dtype->byteorder, ectx.len, NULL); + datatype_free(dtype); mappings = implicit_set_declaration(ctx, "__map%d", key, data, @@ -3203,8 +3202,10 @@ static int stmt_evaluate_addr(struct eval_ctx *ctx, struct stmt *stmt, static int stmt_evaluate_nat_map(struct eval_ctx *ctx, struct stmt *stmt) { struct expr *one, *two, *data, *tmp; - const struct datatype *dtype; - int addr_type, err; + const struct datatype *dtype = NULL; + const struct datatype *dtype2; + int addr_type; + int err; switch (stmt->nat.family) { case NFPROTO_IPV4: @@ -3219,11 +3220,15 @@ static int stmt_evaluate_nat_map(struct eval_ctx *ctx, struct stmt *stmt) dtype = concat_type_alloc((addr_type << TYPE_BITS) | TYPE_INET_SERVICE); expr_set_context(&ctx->ectx, dtype, dtype->size); - if (expr_evaluate(ctx, &stmt->nat.addr)) - return -1; + if (expr_evaluate(ctx, &stmt->nat.addr)) { + err = -1; + goto out; + } - if (stmt->nat.addr->etype != EXPR_MAP) - return 0; + if (stmt->nat.addr->etype != EXPR_MAP) { + err = 0; + goto out; + } data = stmt->nat.addr->mappings->set->data; if (data->flags & EXPR_F_INTERVAL) @@ -3231,36 +3236,42 @@ static int stmt_evaluate_nat_map(struct eval_ctx *ctx, struct stmt *stmt) datatype_set(data, dtype); - if (expr_ops(data)->type != EXPR_CONCAT) - return __stmt_evaluate_arg(ctx, stmt, dtype, dtype->size, + if (expr_ops(data)->type != EXPR_CONCAT) { + err = __stmt_evaluate_arg(ctx, stmt, dtype, dtype->size, BYTEORDER_BIG_ENDIAN, &stmt->nat.addr); + goto out; + } one = list_first_entry(&data->expressions, struct expr, list); two = list_entry(one->list.next, struct expr, list); - if (one == two || !list_is_last(&two->list, &data->expressions)) - return __stmt_evaluate_arg(ctx, stmt, dtype, dtype->size, + if (one == two || !list_is_last(&two->list, &data->expressions)) { + err = __stmt_evaluate_arg(ctx, stmt, dtype, dtype->size, BYTEORDER_BIG_ENDIAN, &stmt->nat.addr); + goto out; + } - dtype = get_addr_dtype(stmt->nat.family); + dtype2 = get_addr_dtype(stmt->nat.family); tmp = one; - err = __stmt_evaluate_arg(ctx, stmt, dtype, dtype->size, + err = __stmt_evaluate_arg(ctx, stmt, dtype2, dtype2->size, BYTEORDER_BIG_ENDIAN, &tmp); if (err < 0) - return err; + goto out; if (tmp != one) BUG("Internal error: Unexpected alteration of l3 expression"); tmp = two; err = nat_evaluate_transport(ctx, stmt, &tmp); if (err < 0) - return err; + goto out; if (tmp != two) BUG("Internal error: Unexpected alteration of l4 expression"); +out: + datatype_free(dtype); return err; } @@ -3941,7 +3952,7 @@ static int set_expr_evaluate_concat(struct eval_ctx *ctx, struct expr **expr) } (*expr)->flags |= flags; - datatype_set(*expr, concat_type_alloc(ntype)); + __datatype_set(*expr, concat_type_alloc(ntype)); (*expr)->len = (*expr)->dtype->size; expr_set_context(&ctx->ectx, (*expr)->dtype, (*expr)->len); diff --git a/src/expression.c b/src/expression.c index cb222a2b..87d5a9fc 100644 --- a/src/expression.c +++ b/src/expression.c @@ -997,7 +997,7 @@ static struct expr *concat_expr_parse_udata(const struct nftnl_udata *attr) if (!dtype) goto err_free; - concat_expr->dtype = datatype_get(dtype); + __datatype_set(concat_expr, dtype); concat_expr->len = dtype->size; return concat_expr; diff --git a/src/netlink.c b/src/netlink.c index 59cde9a4..4d3c1cf1 100644 --- a/src/netlink.c +++ b/src/netlink.c @@ -740,6 +740,10 @@ enum nft_data_types dtype_map_to_kernel(const struct datatype *dtype) static const struct datatype *dtype_map_from_kernel(enum nft_data_types type) { + /* The function always returns ownership of a reference. But for + * &verdict_Type and datatype_lookup(), those are static instances, + * we can omit the datatype_get() call. + */ switch (type) { case NFT_DATA_VERDICT: return &verdict_type; @@ -875,12 +879,14 @@ struct set *netlink_delinearize_set(struct netlink_ctx *ctx, const struct nftnl_udata *ud[NFTNL_UDATA_SET_MAX + 1] = {}; enum byteorder keybyteorder = BYTEORDER_INVALID; enum byteorder databyteorder = BYTEORDER_INVALID; - const struct datatype *keytype, *datatype = NULL; struct expr *typeof_expr_key, *typeof_expr_data; struct setelem_parse_ctx set_parse_ctx; + const struct datatype *datatype = NULL; + const struct datatype *keytype = NULL; + const struct datatype *dtype2 = NULL; + const struct datatype *dtype = NULL; const char *udata, *comment = NULL; uint32_t flags, key, objtype = 0; - const struct datatype *dtype; uint32_t data_interval = 0; bool automerge = false; struct set *set; @@ -932,8 +938,8 @@ struct set *netlink_delinearize_set(struct netlink_ctx *ctx, netlink_io_error(ctx, NULL, "Unknown data type in set key %u", data); - datatype_free(keytype); - return NULL; + set = NULL; + goto out; } } @@ -969,16 +975,15 @@ struct set *netlink_delinearize_set(struct netlink_ctx *ctx, list_splice_tail(&set_parse_ctx.stmt_list, &set->stmt_list); if (datatype) { - dtype = set_datatype_alloc(datatype, databyteorder); + dtype2 = set_datatype_alloc(datatype, databyteorder); klen = nftnl_set_get_u32(nls, NFTNL_SET_DATA_LEN) * BITS_PER_BYTE; if (set_udata_key_valid(typeof_expr_data, dtype, klen)) { - datatype_free(datatype_get(dtype)); set->data = typeof_expr_data; } else { expr_free(typeof_expr_data); set->data = constant_expr_alloc(&netlink_location, - dtype, + dtype2, databyteorder, klen, NULL); @@ -989,16 +994,12 @@ struct set *netlink_delinearize_set(struct netlink_ctx *ctx, if (data_interval) set->data->flags |= EXPR_F_INTERVAL; - - if (dtype != datatype) - datatype_free(datatype); } dtype = set_datatype_alloc(keytype, keybyteorder); klen = nftnl_set_get_u32(nls, NFTNL_SET_KEY_LEN) * BITS_PER_BYTE; if (set_udata_key_valid(typeof_expr_key, dtype, klen)) { - datatype_free(datatype_get(dtype)); set->key = typeof_expr_key; set->key_typeof_valid = true; } else { @@ -1008,9 +1009,6 @@ struct set *netlink_delinearize_set(struct netlink_ctx *ctx, NULL); } - if (dtype != keytype) - datatype_free(keytype); - set->flags = nftnl_set_get_u32(nls, NFTNL_SET_FLAGS); set->handle.handle.id = nftnl_set_get_u64(nls, NFTNL_SET_HANDLE); @@ -1038,6 +1036,11 @@ struct set *netlink_delinearize_set(struct netlink_ctx *ctx, } } +out: + datatype_free(datatype); + datatype_free(keytype); + datatype_free(dtype2); + datatype_free(dtype); return set; } diff --git a/src/netlink_delinearize.c b/src/netlink_delinearize.c index 19c3f0bd..41cb37a3 100644 --- a/src/netlink_delinearize.c +++ b/src/netlink_delinearize.c @@ -2489,7 +2489,7 @@ static void expr_postprocess(struct rule_pp_ctx *ctx, struct expr **exprp) ntype = concat_subtype_add(ntype, i->dtype->type); } - datatype_set(expr, concat_type_alloc(ntype)); + __datatype_set(expr, concat_type_alloc(ntype)); break; } case EXPR_UNARY: -- 2.33.0