[PATCH 4.18 095/228] RDMA/uverbs: Dont overwrite NULL pointer with ZERO_SIZE_PTR

[Greg Kroah-Hartman]

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Leon Romanovsky <leonro@xxxxxxxxxxxx>

[ Upstream commit a5cc9831af05e658543593abaee45a29d061bac4 ]

Number of specs is provided by user and in valid case can be equal to zero.
Such argument causes to call to kcalloc() with zero-length request and in
return the ZERO_SIZE_PTR is assigned. This pointer is different from NULL
and makes various if (..) checks to success.

Fixes: b6ba4a9aa59f ("IB/uverbs: Add support for flow counters")
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/infiniband/core/uverbs_cmd.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -2812,6 +2812,9 @@ static struct ib_uflow_resources *flow_r
 	if (!resources)
 		goto err_res;
 
+	if (!num_specs)
+		goto out;
+
 	resources->counters =
 		kcalloc(num_specs, sizeof(*resources->counters), GFP_KERNEL);
 
@@ -2824,8 +2827,8 @@ static struct ib_uflow_resources *flow_r
 	if (!resources->collection)
 		goto err_collection;
 
+out:
 	resources->max = num_specs;
-
 	return resources;
 
 err_collection: