Re: [rds-devel] KASAN: null-ptr-deref Read in rds_ib_get_mr

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On 2018/5/11 18:46, Sowmini Varadhan wrote:
On (05/11/18 15:48), Yanjun Zhu wrote:
diff --git a/net/rds/ib_rdma.c b/net/rds/ib_rdma.c
index e678699..2228b50 100644
--- a/net/rds/ib_rdma.c
+++ b/net/rds/ib_rdma.c
@@ -539,11 +539,17 @@ void rds_ib_flush_mrs(void)
    void *rds_ib_get_mr(struct scatterlist *sg, unsigned long nents,
                                         struct rds_sock *rs, u32 *key_ret)
    {
-             struct rds_ib_device *rds_ibdev;
+             struct rds_ib_device *rds_ibdev = NULL;
                 struct rds_ib_mr *ibmr = NULL;
-             struct rds_ib_connection *ic = rs->rs_conn->c_transport_data;
+             struct rds_ib_connection *ic = NULL;
                 int ret;

+             if (rs->rs_bound_addr == 0) {
+                             ret = -EPERM;
+                             goto out;
+             }
+
+             ic = rs->rs_conn->c_transport_data;
                 rds_ibdev = rds_ib_get_device(rs->rs_bound_addr);
                 if (!rds_ibdev) {
                                 ret = -ENODEV;

I made this raw patch. If you can reproduce this bug, please make tests
with it.
I dont think this solves the problem, I think it
just changes the timing under which it can still happen.

what if the rds_remove_bound() in rds_bind() happens after the check
for if (rs->rs_bound_addr == 0) added above by the patch

I believe you need some type of synchronization (either
through mutex, or some atomic flag in the rs or similar) to make
sure rds_bind() and rds_ib_get_mr() are mutually exclusive.
Sure. I agree with you. Maybe mutex is a good choice.

Zhu Yanjun

--Sowmini


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