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netfilter: nf_tables: memleak in hw offload abort path

Browse Source 
Release flow from the abort path, this is easy to reproduce since
b72920f6e4 ("netfilter: nftables: counter hardware offload support").
If the preparation phase fails, then the abort path is exercised without
releasing the flow rule object.

unreferenced object 0xffff8881f0fa7700 (size 128):
  comm "nft", pid 1335, jiffies 4294931120 (age 4163.740s)
  hex dump (first 32 bytes):
    08 e4 de 13 82 88 ff ff 98 e4 de 13 82 88 ff ff  ................
    48 e4 de 13 82 88 ff ff 01 00 00 00 00 00 00 00  H...............
  backtrace:
    [<00000000634547e7>] flow_rule_alloc+0x26/0x80
    [<00000000c8426156>] nft_flow_rule_create+0xc9/0x3f0 [nf_tables]
    [<0000000075ff8e46>] nf_tables_newrule+0xc79/0x10a0 [nf_tables]
    [<00000000ba65e40e>] nfnetlink_rcv_batch+0xaac/0xf90 [nfnetlink]
    [<00000000505c614a>] nfnetlink_rcv+0x1bb/0x1f0 [nfnetlink]
    [<00000000eb78e1fe>] netlink_unicast+0x34b/0x480
    [<00000000a8f72c94>] netlink_sendmsg+0x3af/0x690
    [<000000009cb1ddf4>] sock_sendmsg+0x96/0xa0
    [<0000000039d06e44>] ____sys_sendmsg+0x3fe/0x440
    [<00000000137e82ca>] ___sys_sendmsg+0xd8/0x140
    [<000000000c6bf6a6>] __sys_sendmsg+0xb3/0x130
    [<0000000043bd6268>] do_syscall_64+0x40/0xb0
    [<00000000afdebc2d>] entry_SYSCALL_64_after_hwframe+0x44/0xae

Remove flow rule release from the offload commit path, otherwise error
from the offload commit phase might trigger a double-free due to the
execution of the abort_offload -> abort. After this patch, the abort
path takes care of releasing the flow rule.

This fix also needs to move the nft_flow_rule_create() call before the
transaction object is added otherwise the abort path might find a NULL
pointer to the flow rule object for the NFT_CHAIN_HW_OFFLOAD case.

While at it, rename BASIC-like goto tags to slightly more meaningful
names rather than adding a new "err3" tag.

Fixes: 63b48c73ff ("netfilter: nf_tables_offload: undo updates if transaction fails")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Pablo Neira Ayuso 2021-06-19 00:55:20 +02:00
parent 52f0f4e178
commit 3c5e446220
2 changed files with 31 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

51
net/netfilter/nf_tables_api.c
View File

@ -3243,9 +3243,9 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
u8 genmask = nft_genmask_next(info->net);
struct nft_rule *rule, *old_rule = NULL;
struct nft_expr_info *expr_info = NULL;
struct nft_flow_rule *flow = NULL;
int family = nfmsg->nfgen_family;
struct net *net = info->net;
struct nft_flow_rule *flow;
struct nft_userdata *udata;
struct nft_table *table;
struct nft_chain *chain;
@ -3340,13 +3340,13 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
nla_for_each_nested(tmp, nla[NFTA_RULE_EXPRESSIONS], rem) {
err = -EINVAL;
if (nla_type(tmp) != NFTA_LIST_ELEM)
goto err1;
goto err_release_expr;
if (n == NFT_RULE_MAXEXPRS)
goto err1;
goto err_release_expr;
err = nf_tables_expr_parse(&ctx, tmp, &expr_info[n]);
if (err < 0) {
NL_SET_BAD_ATTR(extack, tmp);
goto err1;
goto err_release_expr;
}
size += expr_info[n].ops->size;
n++;
@ -3355,7 +3355,7 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
/* Check for overflow of dlen field */
err = -EFBIG;
if (size >= 1 << 12)
goto err1;
goto err_release_expr;
if (nla[NFTA_RULE_USERDATA]) {
ulen = nla_len(nla[NFTA_RULE_USERDATA]);
@ -3366,7 +3366,7 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
err = -ENOMEM;
rule = kzalloc(sizeof(*rule) + size + usize, GFP_KERNEL);
if (rule == NULL)
goto err1;
goto err_release_expr;
nft_activate_next(net, rule);
@ -3385,7 +3385,7 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
err = nf_tables_newexpr(&ctx, &expr_info[i], expr);
if (err < 0) {
NL_SET_BAD_ATTR(extack, expr_info[i].attr);
goto err2;
goto err_release_rule;
}
if (expr_info[i].ops->validate)
@ -3395,16 +3395,24 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
expr = nft_expr_next(expr);
}
if (chain->flags & NFT_CHAIN_HW_OFFLOAD) {
flow = nft_flow_rule_create(net, rule);
if (IS_ERR(flow)) {
err = PTR_ERR(flow);
goto err_release_rule;
}
}
if (info->nlh->nlmsg_flags & NLM_F_REPLACE) {
trans = nft_trans_rule_add(&ctx, NFT_MSG_NEWRULE, rule);
if (trans == NULL) {
err = -ENOMEM;
goto err2;
goto err_destroy_flow_rule;
}
err = nft_delrule(&ctx, old_rule);
if (err < 0) {
nft_trans_destroy(trans);
goto err2;
goto err_destroy_flow_rule;
}
list_add_tail_rcu(&rule->list, &old_rule->list);
@ -3412,7 +3420,7 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
trans = nft_trans_rule_add(&ctx, NFT_MSG_NEWRULE, rule);
if (!trans) {
err = -ENOMEM;
goto err2;
goto err_destroy_flow_rule;
}
if (info->nlh->nlmsg_flags & NLM_F_APPEND) {
@ -3430,21 +3438,19 @@ static int nf_tables_newrule(struct sk_buff *skb, const struct nfnl_info *info,
kvfree(expr_info);
chain->use++;
if (flow)
nft_trans_flow_rule(trans) = flow;
if (nft_net->validate_state == NFT_VALIDATE_DO)
return nft_table_validate(net, table);
if (chain->flags & NFT_CHAIN_HW_OFFLOAD) {
flow = nft_flow_rule_create(net, rule);
if (IS_ERR(flow))
return PTR_ERR(flow);
nft_trans_flow_rule(trans) = flow;
}
return 0;
err2:
err_destroy_flow_rule:
nft_flow_rule_destroy(flow);
err_release_rule:
nf_tables_rule_release(&ctx, rule);
err1:
err_release_expr:
for (i = 0; i < n; i++) {
if (expr_info[i].ops) {
module_put(expr_info[i].ops->type->owner);
@ -8839,11 +8845,16 @@ static int __nf_tables_abort(struct net *net, enum nfnl_abort_action action)
nft_rule_expr_deactivate(&trans->ctx,
nft_trans_rule(trans),
NFT_TRANS_ABORT);
if (trans->ctx.chain->flags & NFT_CHAIN_HW_OFFLOAD)
nft_flow_rule_destroy(nft_trans_flow_rule(trans));
break;
case NFT_MSG_DELRULE:
trans->ctx.chain->use++;
nft_clear(trans->ctx.net, nft_trans_rule(trans));
nft_rule_expr_activate(&trans->ctx, nft_trans_rule(trans));
if (trans->ctx.chain->flags & NFT_CHAIN_HW_OFFLOAD)
nft_flow_rule_destroy(nft_trans_flow_rule(trans));
nft_trans_destroy(trans);
break;
case NFT_MSG_NEWSET:

17
net/netfilter/nf_tables_offload.c
View File

@ -594,23 +594,6 @@ int nft_flow_rule_offload_commit(struct net *net)
}
}
list_for_each_entry(trans, &nft_net->commit_list, list) {
if (trans->ctx.family != NFPROTO_NETDEV)
continue;
switch (trans->msg_type) {
case NFT_MSG_NEWRULE:
case NFT_MSG_DELRULE:
if (!(trans->ctx.chain->flags & NFT_CHAIN_HW_OFFLOAD))
continue;
nft_flow_rule_destroy(nft_trans_flow_rule(trans));
break;
default:
break;
}
}
return err;
}