linux-kernel - [PATCH AUTOSEL 5.4 03/18] scsi: lpfc: Prevent lpfc_debugfs_lockstat

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Date:   Thu,  4 May 2023 15:50:25 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Justin Tee <justin.tee@...adcom.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Sasha Levin <sashal@...nel.org>, james.smart@...adcom.com,
        dick.kennedy@...adcom.com, jejb@...ux.ibm.com,
        linux-scsi@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 03/18] scsi: lpfc: Prevent lpfc_debugfs_lockstat_write() buffer overflow

From: Justin Tee <justin.tee@...adcom.com>

[ Upstream commit c6087b82a9146826564a55c5ca0164cac40348f5 ]

A static code analysis tool flagged the possibility of buffer overflow when
using copy_from_user() for a debugfs entry.

Currently, it is possible that copy_from_user() copies more bytes than what
would fit in the mybuf char array.  Add a min() restriction check between
sizeof(mybuf) - 1 and nbytes passed from the userspace buffer to protect
against buffer overflow.

Link: https://lore.kernel.org/r/20230301231626.9621-2-justintee8345@gmail.com
Signed-off-by: Justin Tee <justin.tee@...adcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/scsi/lpfc/lpfc_debugfs.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/lpfc/lpfc_debugfs.c b/drivers/scsi/lpfc/lpfc_debugfs.c
index 69551132f304c..291fccf02d453 100644
--- a/drivers/scsi/lpfc/lpfc_debugfs.c
+++ b/drivers/scsi/lpfc/lpfc_debugfs.c
@@ -2046,6 +2046,7 @@ lpfc_debugfs_lockstat_write(struct file *file, const char __user *buf,
 	char mybuf[64];
 	char *pbuf;
 	int i;
+	size_t bsize;
 
 	/* Protect copy from user */
 	if (!access_ok(buf, nbytes))
@@ -2053,7 +2054,9 @@ lpfc_debugfs_lockstat_write(struct file *file, const char __user *buf,
 
 	memset(mybuf, 0, sizeof(mybuf));
 
-	if (copy_from_user(mybuf, buf, nbytes))
+	bsize = min(nbytes, (sizeof(mybuf) - 1));
+
+	if (copy_from_user(mybuf, buf, bsize))
 		return -EFAULT;
 	pbuf = &mybuf[0];
 
@@ -2074,7 +2077,7 @@ lpfc_debugfs_lockstat_write(struct file *file, const char __user *buf,
 			qp->lock_conflict.wq_access = 0;
 		}
 	}
-	return nbytes;
+	return bsize;
 }
 #endif
 
-- 
2.39.2