[PATCH 5.4 138/215] net/rds: fix possible cp null dereference

Greg Kroah-Hartman
2024-04-11T10:20:50Z

From: Mahmoud Adam <mngyadam@amazon.com>

commit 62fc3357e079a07a22465b9b6ef71bb6ea75ee4b upstream.

cp might be null, calling cp->cp_conn would produce null dereference

[Simon Horman adds:]

Analysis:

* cp is a parameter of __rds_rdma_map and is not reassigned.

* The following call-sites pass a NULL cp argument to __rds_rdma_map()

- rds_get_mr()
- rds_get_mr_for_dest

* Prior to the code above, the following assumes that cp may be NULL
(which is indicative, but could itself be unnecessary)

trans_private = rs->rs_transport->get_mr(
sg, nents, rs, &mr->r_key, cp ? cp->cp_conn : NULL,
args->vec.addr, args->vec.bytes,
need_odp ? ODP_ZEROBASED : ODP_NOT_NEEDED);

* The code modified by this patch is guarded by IS_ERR(trans_private),
where trans_private is assigned as per the previous point in this analysis.

The only implementation of get_mr that I could locate is rds_ib_get_mr()
which can return an ERR_PTR if the conn (4th) argument is NULL.

* ret is set to PTR_ERR(trans_private).
rds_ib_get_mr can return ERR_PTR(-ENODEV) if the conn (4th) argument is NULL.
Thus ret may be -ENODEV in which case the code in question will execute.

Conclusion:
* cp may be NULL at the point where this patch adds a check;
this patch does seem to address a possible bug

Fixes: c055fc00c07b ("net/rds: fix WARNING in rds_conn_connect_if_down")
Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: Mahmoud Adam <mngyadam@amazon.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240326153132.55580-1-mngyadam@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/rds/rdma.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/rds/rdma.c
+++ b/net/rds/rdma.c
@@ -280,7 +280,7 @@ static int __rds_rdma_map(struct rds_soc
kfree(sg);
ret = PTR_ERR(trans_private);
/* Trigger connection so that its ready for the next retry */
- if (ret == -ENODEV)
+ if (ret == -ENODEV && cp)
rds_conn_connect_if_down(cp->cp_conn);
goto out;
}