linux-hardening - [PATCH] scsi: message: fusion: replace deprecated strncpy with strscpy

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Message-ID: <20230927-strncpy-drivers-message-fusion-mptsas-c-v1-1-edac65cd7010@google.com>
Date: Wed, 27 Sep 2023 04:43:08 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Sathya Prakash <sathya.prakash@...adcom.com>, 
	Sreekanth Reddy <sreekanth.reddy@...adcom.com>, 
	Suganath Prabu Subramani <suganath-prabu.subramani@...adcom.com>
Cc: MPT-FusionLinux.pdl@...adcom.com, linux-scsi@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org, 
	Kees Cook <keescook@...omium.org>, Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] scsi: message: fusion: 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.

The only caller of mptsas_exp_repmanufacture_info() is
mptsas_probe_one_phy() which can allocate rphy in either
sas_end_device_alloc() or sas_expander_alloc(). Both of which
zero-allocate:
|       rdev = kzalloc(sizeof(*rdev), GFP_KERNEL);
... this is supplied to mptsas_exp_repmanufacture_info() as edev meaning
that no future NUL-padding of edev members is needed.

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.

Note that while `strscpy(dest, src, sizeof(dest))` is more idiomatic
strscpy usage, we should keep `SAS_EXPANDER...LEN` for length arguments
since changing these to sizeof would mean we are getting buffers one
character larger than expected due to the declaration for these members:
|       char   vendor_id[SAS_EXPANDER_VENDOR_ID_LEN+1];
|       char   product_id[SAS_EXPANDER_PRODUCT_ID_LEN+1];
|       char   product_rev[SAS_EXPANDER_PRODUCT_REV_LEN+1];
|       char   component_vendor_id[SAS_EXPANDER_COMPONENT_VENDOR_ID_LEN+1];
... and simply removing the "+1" in conjunction with using sizeof() may
not work as other code may rely on this adjusted buffer length for
sas_expander_device members.

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
Cc: Kees Cook <keescook@...omium.org>
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
Note: build-tested only.

Note: similar to drivers/scsi/mpi3mr/mpi3mr_transport.c +212 which uses
strscpy
---
 drivers/message/fusion/mptsas.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/message/fusion/mptsas.c b/drivers/message/fusion/mptsas.c
index 86f16f3ea478..1dc225701a50 100644
--- a/drivers/message/fusion/mptsas.c
+++ b/drivers/message/fusion/mptsas.c
@@ -2964,15 +2964,15 @@ mptsas_exp_repmanufacture_info(MPT_ADAPTER *ioc,
 			goto out_free;

 		manufacture_reply = data_out + sizeof(struct rep_manu_request);
-		strncpy(edev->vendor_id, manufacture_reply->vendor_id,
+		strscpy(edev->vendor_id, manufacture_reply->vendor_id,
 			SAS_EXPANDER_VENDOR_ID_LEN);
-		strncpy(edev->product_id, manufacture_reply->product_id,
+		strscpy(edev->product_id, manufacture_reply->product_id,
 			SAS_EXPANDER_PRODUCT_ID_LEN);
-		strncpy(edev->product_rev, manufacture_reply->product_rev,
+		strscpy(edev->product_rev, manufacture_reply->product_rev,
 			SAS_EXPANDER_PRODUCT_REV_LEN);
 		edev->level = manufacture_reply->sas_format;
 		if (manufacture_reply->sas_format) {
-			strncpy(edev->component_vendor_id,
+			strscpy(edev->component_vendor_id,
 				manufacture_reply->component_vendor_id,
 				SAS_EXPANDER_COMPONENT_VENDOR_ID_LEN);
 			tmp = (u8 *)&manufacture_reply->component_id;

---
base-commit: 6465e260f48790807eef06b583b38ca9789b6072
change-id: 20230927-strncpy-drivers-message-fusion-mptsas-c-f22d5a4082e2

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