netfilter: conntrack: Fix data-races around ct mark

nf_conn:mark can be read from and written to in parallel. Use
READ_ONCE()/WRITE_ONCE() for reads and writes to prevent unwanted
compiler optimizations.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

5 files changed, 29 insertions, 23 deletions

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index f97bda06d2a9..2692139ce417 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -1781,7 +1781,7 @@ init_conntrack(struct net *net, struct nf_conn *tmpl,
 			}
 
 #ifdef CONFIG_NF_CONNTRACK_MARK
-			ct->mark = exp->master->mark;
+			ct->mark = READ_ONCE(exp->master->mark);
 #endif
 #ifdef CONFIG_NF_CONNTRACK_SECMARK
 			ct->secmark = exp->master->secmark;
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c
index 7562b215b932..d71150a40fb0 100644
--- a/net/netfilter/nf_conntrack_netlink.c
+++ b/net/netfilter/nf_conntrack_netlink.c
@@ -328,9 +328,9 @@ nla_put_failure:
 }
 
 #ifdef CONFIG_NF_CONNTRACK_MARK
-static int ctnetlink_dump_mark(struct sk_buff *skb, const struct nf_conn *ct)
+static int ctnetlink_dump_mark(struct sk_buff *skb, u32 mark)
 {
-	if (nla_put_be32(skb, CTA_MARK, htonl(ct->mark)))
+	if (nla_put_be32(skb, CTA_MARK, htonl(mark)))
 		goto nla_put_failure;
 	return 0;
 
@@ -543,7 +543,7 @@ static int ctnetlink_dump_extinfo(struct sk_buff *skb,
 static int ctnetlink_dump_info(struct sk_buff *skb, struct nf_conn *ct)
 {
 	if (ctnetlink_dump_status(skb, ct) < 0 ||
-	    ctnetlink_dump_mark(skb, ct) < 0 ||
+	    ctnetlink_dump_mark(skb, READ_ONCE(ct->mark)) < 0 ||
 	    ctnetlink_dump_secctx(skb, ct) < 0 ||
 	    ctnetlink_dump_id(skb, ct) < 0 ||
 	    ctnetlink_dump_use(skb, ct) < 0 ||
@@ -722,6 +722,7 @@ ctnetlink_conntrack_event(unsigned int events, const struct nf_ct_event *item)
 	struct sk_buff *skb;
 	unsigned int type;
 	unsigned int flags = 0, group;
+	u32 mark;
 	int err;
 
 	if (events & (1 << IPCT_DESTROY)) {
@@ -826,8 +827,9 @@ ctnetlink_conntrack_event(unsigned int events, const struct nf_ct_event *item)
 	}
 
 #ifdef CONFIG_NF_CONNTRACK_MARK
-	if ((events & (1 << IPCT_MARK) || ct->mark)
-	    && ctnetlink_dump_mark(skb, ct) < 0)
+	mark = READ_ONCE(ct->mark);
+	if ((events & (1 << IPCT_MARK) || mark) &&
+	    ctnetlink_dump_mark(skb, mark) < 0)
 		goto nla_put_failure;
 #endif
 	nlmsg_end(skb, nlh);
@@ -1154,7 +1156,7 @@ static int ctnetlink_filter_match(struct nf_conn *ct, void *data)
 	}
 
 #ifdef CONFIG_NF_CONNTRACK_MARK
-	if ((ct->mark & filter->mark.mask) != filter->mark.val)
+	if ((READ_ONCE(ct->mark) & filter->mark.mask) != filter->mark.val)
 		goto ignore_entry;
 #endif
 	status = (u32)READ_ONCE(ct->status);
@@ -2002,9 +2004,9 @@ static void ctnetlink_change_mark(struct nf_conn *ct,
 		mask = ~ntohl(nla_get_be32(cda[CTA_MARK_MASK]));
 
 	mark = ntohl(nla_get_be32(cda[CTA_MARK]));
-	newmark = (ct->mark & mask) ^ mark;
-	if (newmark != ct->mark)
-		ct->mark = newmark;
+	newmark = (READ_ONCE(ct->mark) & mask) ^ mark;
+	if (newmark != READ_ONCE(ct->mark))
+		WRITE_ONCE(ct->mark, newmark);
 }
 #endif
 
@@ -2669,6 +2671,7 @@ static int __ctnetlink_glue_build(struct sk_buff *skb, struct nf_conn *ct)
 {
 	const struct nf_conntrack_zone *zone;
 	struct nlattr *nest_parms;
+	u32 mark;
 
 	zone = nf_ct_zone(ct);
 
@@ -2730,7 +2733,8 @@ static int __ctnetlink_glue_build(struct sk_buff *skb, struct nf_conn *ct)
 		goto nla_put_failure;
 
 #ifdef CONFIG_NF_CONNTRACK_MARK
-	if (ct->mark && ctnetlink_dump_mark(skb, ct) < 0)
+	mark = READ_ONCE(ct->mark);
+	if (mark && ctnetlink_dump_mark(skb, mark) < 0)
 		goto nla_put_failure;
 #endif
 	if (ctnetlink_dump_labels(skb, ct) < 0)
diff --git a/net/netfilter/nf_conntrack_standalone.c b/net/netfilter/nf_conntrack_standalone.c
index 4ffe84c5a82c..bca839ab1ae8 100644
--- a/net/netfilter/nf_conntrack_standalone.c
+++ b/net/netfilter/nf_conntrack_standalone.c
@@ -366,7 +366,7 @@ static int ct_seq_show(struct seq_file *s, void *v)
 		goto release;
 
 #if defined(CONFIG_NF_CONNTRACK_MARK)
-	seq_printf(s, "mark=%u ", ct->mark);
+	seq_printf(s, "mark=%u ", READ_ONCE(ct->mark));
 #endif
 
 	ct_show_secctx(s, ct);
diff --git a/net/netfilter/nft_ct.c b/net/netfilter/nft_ct.c
index a3f01f209a53..641dc21f92b4 100644
--- a/net/netfilter/nft_ct.c
+++ b/net/netfilter/nft_ct.c
@@ -98,7 +98,7 @@ static void nft_ct_get_eval(const struct nft_expr *expr,
 		return;
 #ifdef CONFIG_NF_CONNTRACK_MARK
 	case NFT_CT_MARK:
-		*dest = ct->mark;
+		*dest = READ_ONCE(ct->mark);
 		return;
 #endif
 #ifdef CONFIG_NF_CONNTRACK_SECMARK
@@ -297,8 +297,8 @@ static void nft_ct_set_eval(const struct nft_expr *expr,
 	switch (priv->key) {
 #ifdef CONFIG_NF_CONNTRACK_MARK
 	case NFT_CT_MARK:
-		if (ct->mark != value) {
-			ct->mark = value;
+		if (READ_ONCE(ct->mark) != value) {
+			WRITE_ONCE(ct->mark, value);
 			nf_conntrack_event_cache(IPCT_MARK, ct);
 		}
 		break;
diff --git a/net/netfilter/xt_connmark.c b/net/netfilter/xt_connmark.c
index e5ebc0810675..ad3c033db64e 100644
--- a/net/netfilter/xt_connmark.c
+++ b/net/netfilter/xt_connmark.c
@@ -30,6 +30,7 @@ connmark_tg_shift(struct sk_buff *skb, const struct xt_connmark_tginfo2 *info)
 	u_int32_t new_targetmark;
 	struct nf_conn *ct;
 	u_int32_t newmark;
+	u_int32_t oldmark;
 
 	ct = nf_ct_get(skb, &ctinfo);
 	if (ct == NULL)
@@ -37,14 +38,15 @@ connmark_tg_shift(struct sk_buff *skb, const struct xt_connmark_tginfo2 *info)
 
 	switch (info->mode) {
 	case XT_CONNMARK_SET:
-		newmark = (ct->mark & ~info->ctmask) ^ info->ctmark;
+		oldmark = READ_ONCE(ct->mark);
+		newmark = (oldmark & ~info->ctmask) ^ info->ctmark;
 		if (info->shift_dir == D_SHIFT_RIGHT)
 			newmark >>= info->shift_bits;
 		else
 			newmark <<= info->shift_bits;
 
-		if (ct->mark != newmark) {
-			ct->mark = newmark;
+		if (READ_ONCE(ct->mark) != newmark) {
+			WRITE_ONCE(ct->mark, newmark);
 			nf_conntrack_event_cache(IPCT_MARK, ct);
 		}
 		break;
@@ -55,15 +57,15 @@ connmark_tg_shift(struct sk_buff *skb, const struct xt_connmark_tginfo2 *info)
 		else
 			new_targetmark <<= info->shift_bits;
 
-		newmark = (ct->mark & ~info->ctmask) ^
+		newmark = (READ_ONCE(ct->mark) & ~info->ctmask) ^
 			  new_targetmark;
-		if (ct->mark != newmark) {
-			ct->mark = newmark;
+		if (READ_ONCE(ct->mark) != newmark) {
+			WRITE_ONCE(ct->mark, newmark);
 			nf_conntrack_event_cache(IPCT_MARK, ct);
 		}
 		break;
 	case XT_CONNMARK_RESTORE:
-		new_targetmark = (ct->mark & info->ctmask);
+		new_targetmark = (READ_ONCE(ct->mark) & info->ctmask);
 		if (info->shift_dir == D_SHIFT_RIGHT)
 			new_targetmark >>= info->shift_bits;
 		else
@@ -126,7 +128,7 @@ connmark_mt(const struct sk_buff *skb, struct xt_action_param *par)
 	if (ct == NULL)
 		return false;
 
-	return ((ct->mark & info->mask) == info->mark) ^ info->invert;
+	return ((READ_ONCE(ct->mark) & info->mask) == info->mark) ^ info->invert;
 }
 
 static int connmark_mt_check(const struct xt_mtchk_param *par)