netfilter: x_tables: check for size overflow

[ Upstream commit d157bd761585605b7882935ffb86286919f62ea1 ]

Ben Hawkes says:
 integer overflow in xt_alloc_table_info, which on 32-bit systems can
 lead to small structure allocation and a copy_from_user based heap
 corruption.

Reported-by: Ben Hawkes <hawkes@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 25391fb255162204b197895647f9c2f3c6d96507..c7b7cecb5bd1a47eed9ea53d3e71dc159d68f8fb 100644 (file)
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -897,6 +897,9 @@ struct xt_table_info *xt_alloc_table_info(unsigned int size)
        struct xt_table_info *info = NULL;
        size_t sz = sizeof(*info) + size;
 
+       if (sz < sizeof(*info))
+               return NULL;
+
        /* Pedantry: prevent them from hitting BUG() in vmalloc.c --RR */
        if ((SMP_ALIGN(size) >> PAGE_SHIFT) + 2 > totalram_pages)
                return NULL;