linux-kernel - [RFC PATCH 3/8] sg_write(): __get

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Message-Id: <20191017193925.25539-3-viro@ZenIV.linux.org.uk>
Date:   Thu, 17 Oct 2019 20:39:20 +0100
From:   Al Viro <viro@...IV.linux.org.uk>
To:     linux-scsi@...r.kernel.org
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>
Subject: [RFC PATCH 3/8] sg_write(): __get_user() can fail...

From: Al Viro <viro@...iv.linux.org.uk>

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
---
 drivers/scsi/sg.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 026628aa556d..4c62237cdf37 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -640,13 +640,15 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
 	if (count < (SZ_SG_HEADER + 6))
 		return -EIO;	/* The minimum scsi command length is 6 bytes. */
 
+	buf += SZ_SG_HEADER;
+	if (__get_user(opcode, buf))
+		return -EFAULT;
+
 	if (!(srp = sg_add_request(sfp))) {
 		SCSI_LOG_TIMEOUT(1, sg_printk(KERN_INFO, sdp,
 					      "sg_write: queue full\n"));
 		return -EDOM;
 	}
-	buf += SZ_SG_HEADER;
-	__get_user(opcode, buf);
 	mutex_lock(&sfp->f_mutex);
 	if (sfp->next_cmd_len > 0) {
 		cmd_size = sfp->next_cmd_len;
-- 
2.11.0