linux-kernel - [PATCH 4.15 13/45] netfilter: x_tables: fix int overflow in xt_alloc_table

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Date:   Fri, 23 Feb 2018 19:28:52 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+4396883fa8c4f64e0175@...kaller.appspotmail.com,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Pablo Neira Ayuso <pablo@...filter.org>
Subject: [PATCH 4.15 13/45] netfilter: x_tables: fix int overflow in xt_alloc_table_info()

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

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

From: Dmitry Vyukov <dvyukov@...gle.com>

commit 889c604fd0b5f6d3b8694ade229ee44124de1127 upstream.

syzkaller triggered OOM kills by passing ipt_replace.size = -1
to IPT_SO_SET_REPLACE. The root cause is that SMP_ALIGN() in
xt_alloc_table_info() causes int overflow and the size check passes
when it should not. SMP_ALIGN() is no longer needed leftover.

Remove SMP_ALIGN() call in xt_alloc_table_info().

Reported-by: syzbot+4396883fa8c4f64e0175@...kaller.appspotmail.com
Signed-off-by: Dmitry Vyukov <dvyukov@...gle.com>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/netfilter/x_tables.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -39,7 +39,6 @@ MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Harald Welte <laforge@...filter.org>");
 MODULE_DESCRIPTION("{ip,ip6,arp,eb}_tables backend module");
 
-#define SMP_ALIGN(x) (((x) + SMP_CACHE_BYTES-1) & ~(SMP_CACHE_BYTES-1))
 #define XT_PCPU_BLOCK_SIZE 4096
 
 struct compat_delta {
@@ -1000,7 +999,7 @@ struct xt_table_info *xt_alloc_table_inf
 		return NULL;
 
 	/* Pedantry: prevent them from hitting BUG() in vmalloc.c --RR */
-	if ((SMP_ALIGN(size) >> PAGE_SHIFT) + 2 > totalram_pages)
+	if ((size >> PAGE_SHIFT) + 2 > totalram_pages)
 		return NULL;
 
 	info = kvmalloc(sz, GFP_KERNEL);