[PATCH 4.14 46/94] RDMA/rxe: Fix the parent sysfs read when the interface has 15 chars

From: Greg Kroah-Hartman
Date: Mon Sep 21 2020 - 12:38:41 EST

From: Yi Zhang <yi.zhang@xxxxxxxxxx>

commit 60b1af64eb35074a4f2d41cc1e503a7671e68963 upstream.

'parent' sysfs reads will yield '\0' bytes when the interface name has 15
chars, and there will no "\n" output.

To reproduce, create one interface with 15 chars:

[root@test ~]# ip a s enp0s29u1u7u3c2
2: enp0s29u1u7u3c2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN group default qlen 1000
link/ether 02:21:28:57:47:17 brd ff:ff:ff:ff:ff:ff
inet6 fe80::ac41:338f:5bcd:c222/64 scope link noprefixroute
valid_lft forever preferred_lft forever
[root@test ~]# modprobe rdma_rxe
[root@test ~]# echo enp0s29u1u7u3c2 > /sys/module/rdma_rxe/parameters/add
[root@test ~]# cat /sys/class/infiniband/rxe0/parent
enp0s29u1u7u3c2[root@test ~]#
[root@test ~]# f="/sys/class/infiniband/rxe0/parent"
[root@test ~]# echo "$(<"$f")"
-bash: warning: command substitution: ignored null byte in input

Use scnprintf and PAGE_SIZE to fill the sysfs output buffer.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 8700e3e7c485 ("Soft RoCE driver")
Link: https://lore.kernel.org/r/20200820153646.31316-1-yi.zhang@xxxxxxxxxx
Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Yi Zhang <yi.zhang@xxxxxxxxxx>
Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/infiniband/sw/rxe/rxe_verbs.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/infiniband/sw/rxe/rxe_verbs.c
+++ b/drivers/infiniband/sw/rxe/rxe_verbs.c
@@ -1178,7 +1178,7 @@ static ssize_t parent_show(struct device
struct rxe_dev *rxe = container_of(device, struct rxe_dev,

- return snprintf(buf, 16, "%s\n", rxe_parent_name(rxe, 1));
+ return scnprintf(buf, PAGE_SIZE, "%s\n", rxe_parent_name(rxe, 1));

static DEVICE_ATTR_RO(parent);