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

[Yanjun Zhu]

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
  

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

[Sowmini Varadhan]

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.

--Sowmini