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Subject[PATCH] ibmvnic: Use strscpy() instead of strncpy()
Date
Since these strings are expected to be NUL-terminated and the buffers
are exactly sized (in vnic_client_data_len()) with no padding, strncpy()
can be safely replaced with strscpy() here, as strncpy() on
NUL-terminated string is considered deprecated[1]. This has the
side-effect of silencing a -Warray-bounds warning due to the compiler
being confused about the vlcd incrementing:

In file included from ./include/linux/string.h:253,
from ./include/linux/bitmap.h:10,
from ./include/linux/cpumask.h:12,
from ./include/linux/mm_types_task.h:14,
from ./include/linux/mm_types.h:5,
from ./include/linux/buildid.h:5,
from ./include/linux/module.h:14,
from drivers/net/ethernet/ibm/ibmvnic.c:35:
In function '__fortify_strncpy',
inlined from 'vnic_add_client_data' at drivers/net/ethernet/ibm/ibmvnic.c:3919:2:
./include/linux/fortify-string.h:39:30: warning: '__builtin_strncpy' offset 12 from the object at 'v
lcd' is out of the bounds of referenced subobject 'name' with type 'char[]' at offset 12 [-Warray-bo
unds]
39 | #define __underlying_strncpy __builtin_strncpy
| ^
./include/linux/fortify-string.h:51:9: note: in expansion of macro '__underlying_strncpy'
51 | return __underlying_strncpy(p, q, size);
| ^~~~~~~~~~~~~~~~~~~~
drivers/net/ethernet/ibm/ibmvnic.c: In function 'vnic_add_client_data':
drivers/net/ethernet/ibm/ibmvnic.c:3883:7: note: subobject 'name' declared here
3883 | char name[];
| ^~~~

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings

Cc: Dany Madden <drt@linux.ibm.com>
Cc: Sukadev Bhattiprolu <sukadev@linux.ibm.com>
Cc: Thomas Falcon <tlfalcon@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
drivers/net/ethernet/ibm/ibmvnic.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c b/drivers/net/ethernet/ibm/ibmvnic.c
index 2d8804ebdf96..adb0d5ca9ff1 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -3909,21 +3909,21 @@ static void vnic_add_client_data(struct ibmvnic_adapter *adapter,
vlcd->type = 1;
len = strlen(os_name) + 1;
vlcd->len = cpu_to_be16(len);
- strncpy(vlcd->name, os_name, len);
+ strscpy(vlcd->name, os_name, len);
vlcd = (struct vnic_login_client_data *)(vlcd->name + len);

/* Type 2 - LPAR name */
vlcd->type = 2;
len = strlen(utsname()->nodename) + 1;
vlcd->len = cpu_to_be16(len);
- strncpy(vlcd->name, utsname()->nodename, len);
+ strscpy(vlcd->name, utsname()->nodename, len);
vlcd = (struct vnic_login_client_data *)(vlcd->name + len);

/* Type 3 - device name */
vlcd->type = 3;
len = strlen(adapter->netdev->name) + 1;
vlcd->len = cpu_to_be16(len);
- strncpy(vlcd->name, adapter->netdev->name, len);
+ strscpy(vlcd->name, adapter->netdev->name, len);
}

static int send_login(struct ibmvnic_adapter *adapter)
--
2.30.2
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