From: Cong Wang cong.wang@bytedance.com
[ Upstream commit 9cd3fd2054c3b3055163accbf2f31a4426f10317 ]
When TCF_EM_SIMPLE was introduced, it is supposed to be convenient for ematch implementation:
https://lore.kernel.org/all/20050105110048.GO26856@postel.suug.ch/
"You don't have to, providing a 32bit data chunk without TCF_EM_SIMPLE set will simply result in allocating & copy. It's an optimization, nothing more."
So if an ematch module provides ops->datalen that means it wants a complex data structure (saved in its em->data) instead of a simple u32 value. We should simply reject such a combination, otherwise this u32 could be misinterpreted as a pointer.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-and-tested-by: syzbot+4caeae4c7103813598ae@syzkaller.appspotmail.com Reported-by: Jun Nie jun.nie@linaro.org Cc: Jamal Hadi Salim jhs@mojatatu.com Cc: Paolo Abeni pabeni@redhat.com Signed-off-by: Cong Wang cong.wang@bytedance.com Acked-by: Paolo Abeni pabeni@redhat.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/sched/ematch.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/net/sched/ematch.c b/net/sched/ematch.c index 113a133ee544..5ba3548d2eb7 100644 --- a/net/sched/ematch.c +++ b/net/sched/ematch.c @@ -259,6 +259,8 @@ static int tcf_em_validate(struct tcf_proto *tp, * the value carried. */ if (em_hdr->flags & TCF_EM_SIMPLE) { + if (em->ops->datalen > 0) + goto errout; if (data_len < sizeof(u32)) goto errout; em->data = *(u32 *) data;