[PATCH 4.16 21/26] netfilter: compat: reject huge allocation requests

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Florian Westphal <fw@strlen.de>

commit 7d7d7e02111e9a4dc9d0658597f528f815d820fd upstream.

no need to bother even trying to allocating huge compat offset arrays,
such ruleset is rejected later on anyway becaus we refuse to allocate
overly large rule blobs.

However, compat translation happens before blob allocation, so we should
add a check there too.

This is supposed to help with fuzzing by avoiding oom-killer.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/netfilter/x_tables.c |   26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -554,14 +554,8 @@ int xt_compat_add_offset(u_int8_t af, un
 {
 	struct xt_af *xp = &xt[af];
 
-	if (!xp->compat_tab) {
-		if (!xp->number)
-			return -EINVAL;
-		xp->compat_tab = vmalloc(sizeof(struct compat_delta) * xp->number);
-		if (!xp->compat_tab)
-			return -ENOMEM;
-		xp->cur = 0;
-	}
+	if (WARN_ON(!xp->compat_tab))
+		return -ENOMEM;
 
 	if (xp->cur >= xp->number)
 		return -EINVAL;
@@ -606,6 +600,22 @@ EXPORT_SYMBOL_GPL(xt_compat_calc_jump);
 
 int xt_compat_init_offsets(u8 af, unsigned int number)
 {
+	size_t mem;
+
+	if (!number || number > (INT_MAX / sizeof(struct compat_delta)))
+		return -EINVAL;
+
+	if (WARN_ON(xt[af].compat_tab))
+		return -EINVAL;
+
+	mem = sizeof(struct compat_delta) * number;
+	if (mem > XT_MAX_TABLE_SIZE)
+		return -ENOMEM;
+
+	xt[af].compat_tab = vmalloc(mem);
+	if (!xt[af].compat_tab)
+		return -ENOMEM;
+
 	xt[af].number = number;
 	xt[af].cur = 0;