linux-hardening - [PATCH v2] scsi: ibmvscsi_tgt: replace deprecated strncpy with strscpy

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Date: Tue, 12 Dec 2023 01:20:20 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Michael Cyr <mikecyr@...ux.ibm.com>, "James E.J. Bottomley" <jejb@...ux.ibm.com>, 
	"Martin K. Petersen" <martin.petersen@...cle.com>
Cc: linux-scsi@...r.kernel.org, target-devel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org, 
	Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH v2] scsi: ibmvscsi_tgt: 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.

We don't need the NUL-padding behavior that strncpy() provides as vscsi
is NUL-allocated in ibmvscsis_probe() which proceeds to call
ibmvscsis_adapter_info():
|       vscsi = kzalloc(sizeof(*vscsi), GFP_KERNEL);

ibmvscsis_probe() -> ibmvscsis_handle_crq() -> ibmvscsis_parse_command()
-> ibmvscsis_mad() -> ibmvscsis_process_mad() -> ibmvscsis_adapter_info()

Following the same idea, `partition_name` is defiend as:
|       static char partition_name[PARTITION_NAMELEN] = "UNKNOWN";
... which is NUL-padded already, meaning strscpy() is the best option.

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

However, for cap->name and info let's use strscpy_pad as they are
allocated via dma_alloc_coherent():
|       cap = dma_alloc_coherent(&vscsi->dma_dev->dev, olen, &token,
|                                GFP_ATOMIC);
&
|       info = dma_alloc_coherent(&vscsi->dma_dev->dev, sizeof(*info), &token,
|                                 GFP_ATOMIC);

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>
---
Changes in v2:
- use strscpy_pad for info->partition_name (thanks Kees)
- rebase onto mainline bee0e7762ad2c602
- Link to v1: https://lore.kernel.org/r/20231030-strncpy-drivers-scsi-ibmvscsi_tgt-ibmvscsi_tgt-c-v1-1-859b5ce257fd@google.com
---
Note: build-tested only.

Found with: $ rg "strncpy\("
---
 drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c b/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c
index 4dc411a58107..6b16020b1f59 100644
--- a/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c
+++ b/drivers/scsi/ibmvscsi_tgt/ibmvscsi_tgt.c
@@ -1551,18 +1551,18 @@ static long ibmvscsis_adapter_info(struct scsi_info *vscsi,
 	if (vscsi->client_data.partition_number == 0)
 		vscsi->client_data.partition_number =
 			be32_to_cpu(info->partition_number);
-	strncpy(vscsi->client_data.srp_version, info->srp_version,
+	strscpy(vscsi->client_data.srp_version, info->srp_version,
 		sizeof(vscsi->client_data.srp_version));
-	strncpy(vscsi->client_data.partition_name, info->partition_name,
+	strscpy(vscsi->client_data.partition_name, info->partition_name,
 		sizeof(vscsi->client_data.partition_name));
 	vscsi->client_data.mad_version = be32_to_cpu(info->mad_version);
 	vscsi->client_data.os_type = be32_to_cpu(info->os_type);
 
 	/* Copy our info */
-	strncpy(info->srp_version, SRP_VERSION,
-		sizeof(info->srp_version));
-	strncpy(info->partition_name, vscsi->dds.partition_name,
-		sizeof(info->partition_name));
+	strscpy_pad(info->srp_version, SRP_VERSION,
+		    sizeof(info->srp_version));
+	strscpy_pad(info->partition_name, vscsi->dds.partition_name,
+		    sizeof(info->partition_name));
 	info->partition_number = cpu_to_be32(vscsi->dds.partition_num);
 	info->mad_version = cpu_to_be32(MAD_VERSION_1);
 	info->os_type = cpu_to_be32(LINUX);
@@ -1645,8 +1645,8 @@ static int ibmvscsis_cap_mad(struct scsi_info *vscsi, struct iu_entry *iue)
 			 be64_to_cpu(mad->buffer),
 			 vscsi->dds.window[LOCAL].liobn, token);
 	if (rc == H_SUCCESS) {
-		strncpy(cap->name, dev_name(&vscsi->dma_dev->dev),
-			SRP_MAX_LOC_LEN);
+		strscpy_pad(cap->name, dev_name(&vscsi->dma_dev->dev),
+			sizeof(cap->name));
 
 		len = olen - min_len;
 		status = VIOSRP_MAD_SUCCESS;
@@ -3650,7 +3650,7 @@ static int ibmvscsis_get_system_info(void)
 
 	name = of_get_property(rootdn, "ibm,partition-name", NULL);
 	if (name)
-		strncpy(partition_name, name, sizeof(partition_name));
+		strscpy(partition_name, name, sizeof(partition_name));
 
 	num = of_get_property(rootdn, "ibm,partition-no", NULL);
 	if (num)

---
base-commit: bee0e7762ad2c6025b9f5245c040fcc36ef2bde8
change-id: 20231030-strncpy-drivers-scsi-ibmvscsi_tgt-ibmvscsi_tgt-c-8a9bd0e54666

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