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Date: Sat, 23 Jul 2016 13:08:39 +0200
From: Pablo Neira Ayuso <pablo@...filter.org>
To: netfilter-devel@...r.kernel.org
Cc: davem@...emloft.net, netdev@...r.kernel.org
Subject: [PATCH 25/25] netfilter: nft_compat: fix crash when related match/target module is removed
From: Liping Zhang <liping.zhang@...eadtrum.com>
We "cache" the loaded match/target modules and reuse them, but when the
modules are removed, we still point to them. Then we may end up with
invalid memory references when using iptables-compat to add rules later.
Input the following commands will reproduce the kernel crash:
# iptables-compat -A INPUT -j LOG
# iptables-compat -D INPUT -j LOG
# rmmod xt_LOG
# iptables-compat -A INPUT -j LOG
BUG: unable to handle kernel paging request at ffffffffa05a9010
IP: [<ffffffff813f783e>] strcmp+0xe/0x30
Call Trace:
[<ffffffffa05acc43>] nft_target_select_ops+0x83/0x1f0 [nft_compat]
[<ffffffffa058a177>] nf_tables_expr_parse+0x147/0x1f0 [nf_tables]
[<ffffffffa058e541>] nf_tables_newrule+0x301/0x810 [nf_tables]
[<ffffffff8141ca00>] ? nla_parse+0x20/0x100
[<ffffffffa057fa8f>] nfnetlink_rcv+0x33f/0x53d [nfnetlink]
[<ffffffffa057f94b>] ? nfnetlink_rcv+0x1fb/0x53d [nfnetlink]
[<ffffffff817116b8>] netlink_unicast+0x178/0x220
[<ffffffff81711a5b>] netlink_sendmsg+0x2fb/0x3a0
[<ffffffff816b7fc8>] sock_sendmsg+0x38/0x50
[<ffffffff816b8a7e>] ___sys_sendmsg+0x28e/0x2a0
[<ffffffff816bcb7e>] ? release_sock+0x1e/0xb0
[<ffffffff81804ac5>] ? _raw_spin_unlock_bh+0x35/0x40
[<ffffffff816bcbe2>] ? release_sock+0x82/0xb0
[<ffffffff816b93d4>] __sys_sendmsg+0x54/0x90
[<ffffffff816b9422>] SyS_sendmsg+0x12/0x20
[<ffffffff81805172>] entry_SYSCALL_64_fastpath+0x1a/0xa9
So when nobody use the related match/target module, there's no need to
"cache" it. And nft_[match|target]_release are useless anymore, remove
them.
Signed-off-by: Liping Zhang <liping.zhang@...eadtrum.com>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
net/netfilter/nft_compat.c | 43 ++++++++++++++++++++-----------------------
1 file changed, 20 insertions(+), 23 deletions(-)
diff --git a/net/netfilter/nft_compat.c b/net/netfilter/nft_compat.c
index 2e07cec..c21e7eb 100644
--- a/net/netfilter/nft_compat.c
+++ b/net/netfilter/nft_compat.c
@@ -23,6 +23,20 @@
#include <linux/netfilter_arp/arp_tables.h>
#include <net/netfilter/nf_tables.h>
+struct nft_xt {
+ struct list_head head;
+ struct nft_expr_ops ops;
+ unsigned int refcnt;
+};
+
+static void nft_xt_put(struct nft_xt *xt)
+{
+ if (--xt->refcnt == 0) {
+ list_del(&xt->head);
+ kfree(xt);
+ }
+}
+
static int nft_compat_chain_validate_dependency(const char *tablename,
const struct nft_chain *chain)
{
@@ -260,6 +274,7 @@ nft_target_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr)
if (par.target->destroy != NULL)
par.target->destroy(&par);
+ nft_xt_put(container_of(expr->ops, struct nft_xt, ops));
module_put(target->me);
}
@@ -442,6 +457,7 @@ nft_match_destroy(const struct nft_ctx *ctx, const struct nft_expr *expr)
if (par.match->destroy != NULL)
par.match->destroy(&par);
+ nft_xt_put(container_of(expr->ops, struct nft_xt, ops));
module_put(match->me);
}
@@ -612,11 +628,6 @@ static const struct nfnetlink_subsystem nfnl_compat_subsys = {
static LIST_HEAD(nft_match_list);
-struct nft_xt {
- struct list_head head;
- struct nft_expr_ops ops;
-};
-
static struct nft_expr_type nft_match_type;
static bool nft_match_cmp(const struct xt_match *match,
@@ -653,6 +664,7 @@ nft_match_select_ops(const struct nft_ctx *ctx,
if (!try_module_get(match->me))
return ERR_PTR(-ENOENT);
+ nft_match->refcnt++;
return &nft_match->ops;
}
}
@@ -673,6 +685,7 @@ nft_match_select_ops(const struct nft_ctx *ctx,
goto err;
}
+ nft_match->refcnt = 1;
nft_match->ops.type = &nft_match_type;
nft_match->ops.size = NFT_EXPR_SIZE(XT_ALIGN(match->matchsize));
nft_match->ops.eval = nft_match_eval;
@@ -690,14 +703,6 @@ err:
return ERR_PTR(err);
}
-static void nft_match_release(void)
-{
- struct nft_xt *nft_match, *tmp;
-
- list_for_each_entry_safe(nft_match, tmp, &nft_match_list, head)
- kfree(nft_match);
-}
-
static struct nft_expr_type nft_match_type __read_mostly = {
.name = "match",
.select_ops = nft_match_select_ops,
@@ -744,6 +749,7 @@ nft_target_select_ops(const struct nft_ctx *ctx,
if (!try_module_get(target->me))
return ERR_PTR(-ENOENT);
+ nft_target->refcnt++;
return &nft_target->ops;
}
}
@@ -764,6 +770,7 @@ nft_target_select_ops(const struct nft_ctx *ctx,
goto err;
}
+ nft_target->refcnt = 1;
nft_target->ops.type = &nft_target_type;
nft_target->ops.size = NFT_EXPR_SIZE(XT_ALIGN(target->targetsize));
nft_target->ops.init = nft_target_init;
@@ -785,14 +792,6 @@ err:
return ERR_PTR(err);
}
-static void nft_target_release(void)
-{
- struct nft_xt *nft_target, *tmp;
-
- list_for_each_entry_safe(nft_target, tmp, &nft_target_list, head)
- kfree(nft_target);
-}
-
static struct nft_expr_type nft_target_type __read_mostly = {
.name = "target",
.select_ops = nft_target_select_ops,
@@ -835,8 +834,6 @@ static void __exit nft_compat_module_exit(void)
nfnetlink_subsys_unregister(&nfnl_compat_subsys);
nft_unregister_expr(&nft_target_type);
nft_unregister_expr(&nft_match_type);
- nft_match_release();
- nft_target_release();
}
MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_NFT_COMPAT);
--
2.1.4
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