[PATCH 5.2 224/313] RDMA: Fix double-free in srq creation error flow

[Greg Kroah-Hartman]

From: Jack Morgenstein <jackm@xxxxxxxxxxxxxxxxxx>

commit 3eca7fc2d8d1275d9cf0c709f0937becbfcf6d96 upstream.

The cited commit introduced a double-free of the srq buffer in the error
flow of procedure __uverbs_create_xsrq().

The problem is that ib_destroy_srq_user() called in the error flow also
frees the srq buffer.

Thus, if uverbs_response() fails in __uverbs_create_srq(), the srq buffer
will be freed twice.

Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: 68e326dea1db ("RDMA: Handle SRQ allocations by IB/core")
Link: https://lore.kernel.org/r/20190916071154.20383-5-leon@xxxxxxxxxx
Signed-off-by: Jack Morgenstein <jackm@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/infiniband/core/uverbs_cmd.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/infiniband/core/uverbs_cmd.c
+++ b/drivers/infiniband/core/uverbs_cmd.c
@@ -3477,7 +3477,8 @@ static int __uverbs_create_xsrq(struct u
 
 err_copy:
 	ib_destroy_srq_user(srq, uverbs_get_cleared_udata(attrs));
-
+	/* It was released in ib_destroy_srq_user */
+	srq = NULL;
 err_free:
 	kfree(srq);
 err_put: