linux-hardening - [PATCH] scsi: zfcp: Replace strlcpy() with strscpy()

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Date: Thu, 16 Nov 2023 11:14:35 -0800
From: Kees Cook <keescook@...omium.org>
To: Steffen Maier <maier@...ux.ibm.com>
Cc: Kees Cook <keescook@...omium.org>,
	Benjamin Block <bblock@...ux.ibm.com>,
	Heiko Carstens <hca@...ux.ibm.com>,
	Vasily Gorbik <gor@...ux.ibm.com>,
	Alexander Gordeev <agordeev@...ux.ibm.com>,
	Christian Borntraeger <borntraeger@...ux.ibm.com>,
	Sven Schnelle <svens@...ux.ibm.com>,
	Azeem Shaikh <azeemshaikh38@...il.com>,
	linux-s390@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH] scsi: zfcp: Replace strlcpy() with strscpy()

strlcpy() reads the entire source buffer first. This read may exceed
the destination size limit. This is both inefficient and can lead
to linear read overflows if a source string is not NUL-terminated[1].
Additionally, it returns the size of the source string, not the
resulting size of the destination string. In an effort to remove strlcpy()
completely[2], replace strlcpy() here with strscpy().

Be explicitly robust in the face of truncation, which should be an
impossible state.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy [1]
Link: https://github.com/KSPP/linux/issues/89 [2]
Cc: Steffen Maier <maier@...ux.ibm.com>
Cc: Benjamin Block <bblock@...ux.ibm.com>
Cc: Heiko Carstens <hca@...ux.ibm.com>
Cc: Vasily Gorbik <gor@...ux.ibm.com>
Cc: Alexander Gordeev <agordeev@...ux.ibm.com>
Cc: Christian Borntraeger <borntraeger@...ux.ibm.com>
Cc: Sven Schnelle <svens@...ux.ibm.com>
Cc: Azeem Shaikh <azeemshaikh38@...il.com>
Cc: linux-s390@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/s390/scsi/zfcp_fc.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/scsi/zfcp_fc.c b/drivers/s390/scsi/zfcp_fc.c
index 4f0d0e55f0d4..1a29f10767fc 100644
--- a/drivers/s390/scsi/zfcp_fc.c
+++ b/drivers/s390/scsi/zfcp_fc.c
@@ -900,8 +900,15 @@ static void zfcp_fc_rspn(struct zfcp_adapter *adapter,
 	zfcp_fc_ct_ns_init(&rspn_req->ct_hdr, FC_NS_RSPN_ID,
 			   FC_SYMBOLIC_NAME_SIZE);
 	hton24(rspn_req->rspn.fr_fid.fp_fid, fc_host_port_id(shost));
-	len = strlcpy(rspn_req->rspn.fr_name, fc_host_symbolic_name(shost),
-		      FC_SYMBOLIC_NAME_SIZE);
+	len = strscpy(rspn_req->name, fc_host_symbolic_name(shost),
+		      sizeof(rspn_req->name));
+	/*
+	 * It should be impossible for this to truncate, as
+	 * sizeof(rspn_req->name) is equal to max size of
+	 * fc_host_symbolic_name(shost), but check anyway.
+	 */
+	if (len < 0)
+		len = sizeof(rspn_req->name) - 1;
 	rspn_req->rspn.fr_name_len = len;
 
 	sg_init_one(&fc_req->sg_req, rspn_req, sizeof(*rspn_req));
-- 
2.34.1