Commit 889c604f authored Dec 28, 2017 by Dmitry Vyukov Committed by Pablo Neira Ayuso Jan 07, 2018

netfilter: x_tables: fix int overflow in xt_alloc_table_info()



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@syzkaller.appspotmail.com>
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

parent d1616f07

net/netfilter/x_tables.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -39,7 +39,6 @@ MODULE_LICENSE("GPL");
		MODULE_AUTHOR("Harald Welte <laforge@netfilter.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_info(unsigned int size)
		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);