Messages in this thread | | | Subject | Re: [PATCH] netlink: add buffer boundary checking | From | Jacob Keller <> | Date | Fri, 24 Jul 2020 14:14:25 -0700 |
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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 <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. > >
I also think this is a better approach.
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