linux-hardening - [PATCH] ibmvmc: replace deprecated strncpy with strscpy

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Message-ID: <20230927-strncpy-drivers-misc-ibmvmc-c-v1-1-29f56cd3a269@google.com>
Date: Wed, 27 Sep 2023 05:52:14 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Brad Warrum <bwarrum@...ux.ibm.com>, Ritu Agarwal <rituagar@...ux.ibm.com>, 
	Arnd Bergmann <arnd@...db.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org, 
	Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] ibmvmc: replace deprecated strncpy with strscpy

`strncpy` is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

A suitable replacement is `strscpy` [2] due to the fact that it
guarantees NUL-termination on the destination buffer without
unnecessarily NUL-padding.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
Note: build-tested only.
---
 drivers/misc/ibmvmc.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/misc/ibmvmc.c b/drivers/misc/ibmvmc.c
index 2101eb12bcba..6d9ed9325f9f 100644
--- a/drivers/misc/ibmvmc.c
+++ b/drivers/misc/ibmvmc.c
@@ -1249,9 +1249,7 @@ static long ibmvmc_ioctl_sethmcid(struct ibmvmc_file_session *session,
 		return -EIO;
 	}
 
-	/* Make sure buffer is NULL terminated before trying to print it */
-	memset(print_buffer, 0, HMC_ID_LEN + 1);
-	strncpy(print_buffer, hmc->hmc_id, HMC_ID_LEN);
+	strscpy(print_buffer, hmc->hmc_id, sizeof(print_buffer));
 	pr_info("ibmvmc: sethmcid: Set HMC ID: \"%s\"\n", print_buffer);
 
 	memcpy(buffer->real_addr_local, hmc->hmc_id, HMC_ID_LEN);

---
base-commit: 6465e260f48790807eef06b583b38ca9789b6072
change-id: 20230927-strncpy-drivers-misc-ibmvmc-c-534349716fa4

Best regards,
--
Justin Stitt <justinstitt@...gle.com>