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Date:   Thu, 26 Oct 2023 23:13:41 +0000
Mime-Version: 1.0
Message-ID: <20231026-strncpy-drivers-scsi-hpsa-c-v2-1-2fe2d05122fd@google.com>
Subject: [PATCH v2] scsi: hpsa: replace deprecated strncpy
From:   Justin Stitt <justinstitt@google.com>
To:     Don Brace <don.brace@microchip.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>
Cc:     storagedev@microchip.com, linux-scsi@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org,
        Kees Cook <keescook@chromium.org>,
        Justin Stitt <justinstitt@google.com>
Content-Type: text/plain; charset="utf-8"
Precedence: bulk

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

Instances of strncpy()'ing a string into a buffer and manually
NUL-terminating followed by sccanf with just "%d" as the format
specifier can be accomplished by strscpy() and kstrtoint().

strscpy() guarantees NUL-termination on the destination buffer and
kstrtoint is better way of getting strings turned into ints.

For the last two strncpy() use cases in init_driver_version(), we can
actually drop this function entirely.

Firstly, we are kmalloc()'ing driver_version. Then, we are calling
init_driver_version() which memset's it to 0 followed by a strncpy().
The pattern is 1) allocating memory for a string, 2) setting all bytes
to NUL, 3) copy bytes from another string + ensure NUL-padded.

For these, we can just stack allocate driver_version and
old_driver_version. This simplifies the code greatly as we don't have
any malloc/free or strncpy's.

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@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Justin Stitt <justinstitt@google.com>
---
Changes in v2:
- use stack for buffers (thanks Kees)
- use kstrtoint (thanks Kees)
- Link to v1: https://lore.kernel.org/r/20231026-strncpy-drivers-scsi-hpsa-c-v1-1-75519d7a191b@google.com
---
Note: build-tested only.

Found with: $ rg "strncpy\("
---
 drivers/scsi/hpsa.c | 53 ++++++++++++++++++++---------------------------------
 1 file changed, 20 insertions(+), 33 deletions(-)

diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
index af18d20f3079..4d42fbb071cf 100644
--- a/drivers/scsi/hpsa.c
+++ b/drivers/scsi/hpsa.c
@@ -452,18 +452,18 @@ static ssize_t host_store_hp_ssd_smart_path_status(struct device *dev,
 					 struct device_attribute *attr,
 					 const char *buf, size_t count)
 {
-	int status, len;
+	int status;
 	struct ctlr_info *h;
 	struct Scsi_Host *shost = class_to_shost(dev);
 	char tmpbuf[10];
 
 	if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
 		return -EACCES;
-	len = count > sizeof(tmpbuf) - 1 ? sizeof(tmpbuf) - 1 : count;
-	strncpy(tmpbuf, buf, len);
-	tmpbuf[len] = '\0';
-	if (sscanf(tmpbuf, "%d", &status) != 1)
+
+	strscpy(tmpbuf, buf, sizeof(tmpbuf));
+	if (kstrtoint(tmpbuf, 0, &status))
 		return -EINVAL;
+
 	h = shost_to_hba(shost);
 	h->acciopath_status = !!status;
 	dev_warn(&h->pdev->dev,
@@ -476,18 +476,18 @@ static ssize_t host_store_raid_offload_debug(struct device *dev,
 					 struct device_attribute *attr,
 					 const char *buf, size_t count)
 {
-	int debug_level, len;
+	int debug_level;
 	struct ctlr_info *h;
 	struct Scsi_Host *shost = class_to_shost(dev);
 	char tmpbuf[10];
 
 	if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
 		return -EACCES;
-	len = count > sizeof(tmpbuf) - 1 ? sizeof(tmpbuf) - 1 : count;
-	strncpy(tmpbuf, buf, len);
-	tmpbuf[len] = '\0';
-	if (sscanf(tmpbuf, "%d", &debug_level) != 1)
+
+	strscpy(tmpbuf, buf, sizeof(tmpbuf));
+	if (kstrtoint(tmpbuf, 0, &debug_level))
 		return -EINVAL;
+
 	if (debug_level < 0)
 		debug_level = 0;
 	h = shost_to_hba(shost);
@@ -7234,25 +7234,15 @@ static int hpsa_controller_hard_reset(struct pci_dev *pdev,
 	return 0;
 }
 
-static void init_driver_version(char *driver_version, int len)
-{
-	memset(driver_version, 0, len);
-	strncpy(driver_version, HPSA " " HPSA_DRIVER_VERSION, len - 1);
-}
-
 static int write_driver_ver_to_cfgtable(struct CfgTable __iomem *cfgtable)
 {
-	char *driver_version;
 	int i, size = sizeof(cfgtable->driver_version);
+	char driver_version[sizeof(cfgtable->driver_version)] =
+						HPSA " " HPSA_DRIVER_VERSION;
 
-	driver_version = kmalloc(size, GFP_KERNEL);
-	if (!driver_version)
-		return -ENOMEM;
-
-	init_driver_version(driver_version, size);
 	for (i = 0; i < size; i++)
 		writeb(driver_version[i], &cfgtable->driver_version[i]);
-	kfree(driver_version);
+
 	return 0;
 }
 
@@ -7268,21 +7258,18 @@ static void read_driver_ver_from_cfgtable(struct CfgTable __iomem *cfgtable,
 static int controller_reset_failed(struct CfgTable __iomem *cfgtable)
 {
 
-	char *driver_ver, *old_driver_ver;
-	int rc, size = sizeof(cfgtable->driver_version);
-
-	old_driver_ver = kmalloc_array(2, size, GFP_KERNEL);
-	if (!old_driver_ver)
-		return -ENOMEM;
-	driver_ver = old_driver_ver + size;
+	char driver_ver[sizeof(cfgtable->driver_version)] = "";
+	char old_driver_ver[sizeof(cfgtable->driver_version)] =
+						HPSA " " HPSA_DRIVER_VERSION;
+	int rc;
 
 	/* After a reset, the 32 bytes of "driver version" in the cfgtable
 	 * should have been changed, otherwise we know the reset failed.
 	 */
-	init_driver_version(old_driver_ver, size);
 	read_driver_ver_from_cfgtable(cfgtable, driver_ver);
-	rc = !memcmp(driver_ver, old_driver_ver, size);
-	kfree(old_driver_ver);
+	rc = !memcmp(driver_ver, old_driver_ver,
+		     sizeof(cfgtable->driver_version));
+
 	return rc;
 }
 /* This does a hard reset of the controller using PCI power management

---
base-commit: d88520ad73b79e71e3ddf08de335b8520ae41c5c
change-id: 20231026-strncpy-drivers-scsi-hpsa-c-4cb7bd4e9b7f

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