On 7/23/2020 12:35 PM, Eric Dumazet wrote:
> On 7/23/20 11:21 AM, Mark Salyzyn wrote:
>> Many of the nla_get_* inlines fail to check attribute's length before
>> copying the content resulting in possible out-of-boundary accesses.
>> Adjust the inlines to perform nla_len checking, for the most part
>> using the nla_memcpy function to faciliate since these are not
>> necessarily performance critical and do not need a likely fast path.
>>
>> Signed-off-by: Mark Salyzyn <saly...@android.com>
>> Cc: netdev@vger.kernel.org
>> Cc: linux-ker...@vger.kernel.org
>> Cc: kernel-t...@android.com
>> Cc: "David S. Miller" <da...@davemloft.net>
>> Cc: Jakub Kicinski <k...@kernel.org>
>> Cc: Thomas Graf <tg...@suug.ch>
>> Fixes: bfa83a9e03cf ("[NETLINK]: Type-safe netlink messages/attributes
>> interface")
>> ---
>> include/net/netlink.h | 66 +++++++++++++++++++++++++++++++++++--------
>> 1 file changed, 54 insertions(+), 12 deletions(-)
>>
>> diff --git a/include/net/netlink.h b/include/net/netlink.h
>> index c0411f14fb53..11c0f153be7c 100644
>> --- a/include/net/netlink.h
>> +++ b/include/net/netlink.h
>> @@ -1538,7 +1538,11 @@ static inline int nla_put_bitfield32(struct sk_buff
>> *skb, int attrtype,
>> */
>> static inline u32 nla_get_u32(const struct nlattr *nla)
>> {
>> - return *(u32 *) nla_data(nla);
>> + u32 tmp;
>> +
>> + nla_memcpy(&tmp, nla, sizeof(tmp));
>> +
>> + return tmp;
>
> I believe this will hide bugs, that syzbot was able to catch.
>
> Instead, you could perhaps introduce a CONFIG_DEBUG_NETLINK option,
> and add a WARN_ON_ONCE(nla_len(nla) < sizeof(u32)) so that we can detect bugs
> in callers.
>
>
I also think this is a better approach.
