netdev - [PATCH net 2/2] net/mlx4_core: Fix error handling when initializing CQ bufs in the driver

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Date:   Tue, 22 Jan 2019 15:19:45 +0200
From:   Tariq Toukan <tariqt@...lanox.com>
To:     "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, Eran Ben Elisha <eranbe@...lanox.com>,
        Jack Morgenstein <jackm@....mellanox.co.il>,
        Tariq Toukan <tariqt@...lanox.com>
Subject: [PATCH net 2/2] net/mlx4_core: Fix error handling when initializing CQ bufs in the driver

From: Jack Morgenstein <jackm@....mellanox.co.il>

Procedure mlx4_init_user_cqes() handles returns by copy_to_user
incorrectly. copy_to_user() returns the number of bytes not copied.
Thus, a non-zero return should be treated as a -EFAULT error
(as is done elsewhere in the kernel). However, mlx4_init_user_cqes()
error handling simply returns the number of bytes not copied
(instead of -EFAULT).

Note, though, that this is a harmless bug: procedure mlx4_alloc_cq()
(which is the only caller of mlx4_init_user_cqes()) treats any
non-zero return as an error, but that returned error value is processed
internally, and not passed further up the call stack.

In addition, fixes the following sparse warning:
warning: incorrect type in argument 1 (different address spaces)
   expected void [noderef] <asn:1>*to
   got void *buf

Fixes: e45678973dcb ("{net, IB}/mlx4: Initialize CQ buffers in the driver when possible")
Reported by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Jack Morgenstein <jackm@....mellanox.co.il>
Signed-off-by: Tariq Toukan <tariqt@...lanox.com>
---
 drivers/net/ethernet/mellanox/mlx4/cq.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/cq.c b/drivers/net/ethernet/mellanox/mlx4/cq.c
index db909b6069b5..65f8a4b6ed0c 100644
--- a/drivers/net/ethernet/mellanox/mlx4/cq.c
+++ b/drivers/net/ethernet/mellanox/mlx4/cq.c
@@ -306,14 +306,16 @@ static int mlx4_init_user_cqes(void *buf, int entries, int cqe_size)
 
 	if (entries_per_copy < entries) {
 		for (i = 0; i < entries / entries_per_copy; i++) {
-			err = copy_to_user(buf, init_ents, PAGE_SIZE);
+			err = copy_to_user((void __user *)buf, init_ents, PAGE_SIZE) ?
+				-EFAULT : 0;
 			if (err)
 				goto out;
 
 			buf += PAGE_SIZE;
 		}
 	} else {
-		err = copy_to_user(buf, init_ents, entries * cqe_size);
+		err = copy_to_user((void __user *)buf, init_ents, entries * cqe_size) ?
+			-EFAULT : 0;
 	}
 
 out:
-- 
1.8.3.1