linux-hardening - [PATCH v3 5/7] scsi: devinfo: replace strncpy and manual pad

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Date: Tue, 05 Mar 2024 23:34:40 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Sathya Prakash Veerichetty <sathya.prakash@...adcom.com>, Kashyap Desai <kashyap.desai@...adcom.com>, 
	Sumit Saxena <sumit.saxena@...adcom.com>, Sreekanth Reddy <sreekanth.reddy@...adcom.com>, 
	"James E.J. Bottomley" <jejb@...ux.ibm.com>, "Martin K. Petersen" <martin.petersen@...cle.com>, 
	Suganath Prabu Subramani <suganath-prabu.subramani@...adcom.com>, Ariel Elior <aelior@...vell.com>, 
	Manish Chopra <manishc@...vell.com>, "David S. Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	Saurav Kashyap <skashyap@...vell.com>, Javed Hasan <jhasan@...vell.com>, 
	GR-QLogic-Storage-Upstream@...vell.com, Nilesh Javali <njavali@...vell.com>, 
	Manish Rangankar <mrangankar@...vell.com>, Don Brace <don.brace@...rochip.com>
Cc: mpi3mr-linuxdrv.pdl@...adcom.com, linux-scsi@...r.kernel.org, 
	linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Kees Cook <keescook@...omium.org>, MPT-FusionLinux.pdl@...adcom.com, 
	netdev@...r.kernel.org, storagedev@...rochip.com, 
	Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH v3 5/7] scsi: devinfo: replace strncpy and manual pad

Depending on the state of @compatible, we are going to do different
things with our @to buffer.

When @compatible is true we want a NUL-term'd and NUL-padded destination
buffer. Conversely, if @compatible is false we just want a space-padded
destination buffer (no NUL-term required).

As per:
/**
 * scsi_dev_info_list_add_keyed - add one dev_info list entry.
 * @compatible: if true, null terminate short strings.  Otherwise space pad.
...

Note that we can't easily use `strtomem_pad` here as the size of the @to
buffer is unknown to the compiler due to indirection layers.

Now, the intent of the code is more clear (I probably didn't even need
to add a comment -- that's how clear it is).

Reviewed-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
 drivers/scsi/scsi_devinfo.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/scsi_devinfo.c b/drivers/scsi/scsi_devinfo.c
index 3fcaf10a9dfe..2d3dbce25629 100644
--- a/drivers/scsi/scsi_devinfo.c
+++ b/drivers/scsi/scsi_devinfo.c
@@ -293,14 +293,16 @@ static void scsi_strcpy_devinfo(char *name, char *to, size_t to_length,
 	size_t from_length;
 
 	from_length = strlen(from);
-	/* This zero-pads the destination */
-	strncpy(to, from, to_length);
-	if (from_length < to_length && !compatible) {
-		/*
-		 * space pad the string if it is short.
-		 */
-		memset(&to[from_length], ' ', to_length - from_length);
-	}
+
+	/*
+	 * null pad and null terminate if compatible
+	 * otherwise space pad
+	 */
+	if (compatible)
+		strscpy_pad(to, from, to_length);
+	else
+		memcpy_and_pad(to, to_length, from, from_length, ' ');
+
 	if (from_length > to_length)
 		 printk(KERN_WARNING "%s: %s string '%s' is too long\n",
 			__func__, name, from);

-- 
2.44.0.278.ge034bb2e1d-goog