[PATCH] lustre: check copy_from_iter/copy_to_iter return code

[Arnd Bergmann <arnd@arndb.de>]

We now get a helpful warning for code that calls copy_{from,to}_iter
without checking the return value, introduced by commit aa28de275a24
("iov_iter/hardening: move object size checks to inlined part").

drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c: In function 'kiblnd_send':
drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c:1643:2: error: ignoring return value of 'copy_from_iter', declared with attribute warn_unused_result [-Werror=unused-result]
drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c: In function 'kiblnd_recv':
drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c:1744:3: error: ignoring return value of 'copy_to_iter', declared with attribute warn_unused_result [-Werror=unused-result]

In case we get short copies here, we may get incorrect behavior.
I've added failure handling for both rx and tx now, returning
-EFAULT as expected.

Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
This warning now shows up in 'allmodconfig' builds, so it would be
good to get it fixed quickly for 4.13, but my patch should not go
in without careful review since I'm not familiar with with code
and the error handling is a bit tricky here.

I added 'Cc: stable' since this is a preexisting condition that we
only started warning about now.
---
 drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
index 85b242ec5f9b..70256a0ffd2e 100644
--- a/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
+++ b/drivers/staging/lustre/lnet/klnds/o2iblnd/o2iblnd_cb.c
@@ -1640,8 +1640,13 @@ kiblnd_send(struct lnet_ni *ni, void *private, struct lnet_msg *lntmsg)
 	ibmsg = tx->tx_msg;
 	ibmsg->ibm_u.immediate.ibim_hdr = *hdr;
 
-	copy_from_iter(&ibmsg->ibm_u.immediate.ibim_payload, IBLND_MSG_SIZE,
+	rc = copy_from_iter(&ibmsg->ibm_u.immediate.ibim_payload, IBLND_MSG_SIZE,
 		       &from);
+	if (rc != IBLND_MSG_SIZE) {
+		kiblnd_pool_free_node(&tx->tx_pool->tpo_pool, &tx->tx_list);
+		return -EFAULT;
+	}
+
 	nob = offsetof(struct kib_immediate_msg, ibim_payload[payload_nob]);
 	kiblnd_init_tx_msg(ni, tx, IBLND_MSG_IMMEDIATE, nob);
 
@@ -1741,8 +1746,14 @@ kiblnd_recv(struct lnet_ni *ni, void *private, struct lnet_msg *lntmsg,
 			break;
 		}
 
-		copy_to_iter(&rxmsg->ibm_u.immediate.ibim_payload,
+		rc = copy_to_iter(&rxmsg->ibm_u.immediate.ibim_payload,
 			     IBLND_MSG_SIZE, to);
+		if (rc != IBLND_MSG_SIZE) {
+			rc = -EFAULT;
+			break;
+		}
+
+		rc = 0;
 		lnet_finalize(ni, lntmsg, 0);
 		break;
 
-- 
2.9.0