Messages in this thread | | | Subject | Re: [PATCH] netlink: add buffer boundary checking | From | Eric Dumazet <> | Date | Thu, 23 Jul 2020 12:35:24 -0700 |
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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 <salyzyn@android.com> > Cc: netdev@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Cc: kernel-team@android.com > Cc: "David S. Miller" <davem@davemloft.net> > Cc: Jakub Kicinski <kuba@kernel.org> > Cc: Thomas Graf <tgraf@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.
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