linux-hardening - [PATCH 03/64] rpmsg: glink: Replace strncpy() with strscpy

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Date:   Tue, 27 Jul 2021 13:57:54 -0700
From:   Kees Cook <keescook@...omium.org>
To:     linux-hardening@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Keith Packard <keithpac@...zon.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        netdev@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-staging@...ts.linux.dev, linux-block@...r.kernel.org,
        linux-kbuild@...r.kernel.org, clang-built-linux@...glegroups.com
Subject: [PATCH 03/64] rpmsg: glink: Replace strncpy() with strscpy_pad()

The use of strncpy() is considered deprecated for NUL-terminated
strings[1]. Replace strncpy() with strscpy_pad() (as it seems this case
expects the NUL padding to fill the allocation following the flexible
array). This additionally silences a warning seen when building under
-Warray-bounds:

./include/linux/fortify-string.h:38:30: warning: '__builtin_strncpy' offset 24 from the object at '__mptr' is out of the bounds of referenced subobject 'data' with type 'u8[]' {aka 'unsigned char[]'} at offset 24 [-Warray-bounds]
   38 | #define __underlying_strncpy __builtin_strncpy
      |                              ^
./include/linux/fortify-string.h:50:9: note: in expansion of macro '__underlying_strncpy'
   50 |  return __underlying_strncpy(p, q, size);
      |         ^~~~~~~~~~~~~~~~~~~~
drivers/rpmsg/qcom_glink_native.c: In function 'qcom_glink_work':
drivers/rpmsg/qcom_glink_native.c:36:5: note: subobject 'data' declared here
   36 |  u8 data[];
      |     ^~~~

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

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/rpmsg/qcom_glink_native.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/rpmsg/qcom_glink_native.c b/drivers/rpmsg/qcom_glink_native.c
index 05533c71b10e..c7b9de655080 100644
--- a/drivers/rpmsg/qcom_glink_native.c
+++ b/drivers/rpmsg/qcom_glink_native.c
@@ -1440,7 +1440,7 @@ static int qcom_glink_rx_open(struct qcom_glink *glink, unsigned int rcid,
 		}
 
 		rpdev->ept = &channel->ept;
-		strncpy(rpdev->id.name, name, RPMSG_NAME_SIZE);
+		strscpy_pad(rpdev->id.name, name, RPMSG_NAME_SIZE);
 		rpdev->src = RPMSG_ADDR_ANY;
 		rpdev->dst = RPMSG_ADDR_ANY;
 		rpdev->ops = &glink_device_ops;
-- 
2.30.2