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[173.230.104.22]) by smtp.gmail.com with ESMTPSA id y3sm15643619iol.55.2018.12.25.12.16.24 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 25 Dec 2018 12:16:24 -0800 (PST) From: Kangjie Lu To: kjlu@umn.edu Cc: pakki001@umn.edu, Doug Gilbert , "James E.J. Bottomley" , "Martin K. Petersen" , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] scsi: avoid a double-fetch and a redundant copy Date: Tue, 25 Dec 2018 14:15:54 -0600 Message-Id: <20181225201554.69395-1-kjlu@umn.edu> X-Mailer: git-send-email 2.17.2 (Apple Git-113) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org What we need is only "pack_id", so do not create a heap object or copy the whole object in. The fix efficiently copies "pack_id" only. Signed-off-by: Kangjie Lu --- drivers/scsi/sg.c | 12 ++---------- 1 file changed, 2 insertions(+), 10 deletions(-) diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c index c6ad00703c5b..4dacbfffd113 100644 --- a/drivers/scsi/sg.c +++ b/drivers/scsi/sg.c @@ -446,16 +446,8 @@ sg_read(struct file *filp, char __user *buf, size_t count, loff_t * ppos) } if (old_hdr->reply_len < 0) { if (count >= SZ_SG_IO_HDR) { - sg_io_hdr_t *new_hdr; - new_hdr = kmalloc(SZ_SG_IO_HDR, GFP_KERNEL); - if (!new_hdr) { - retval = -ENOMEM; - goto free_old_hdr; - } - retval =__copy_from_user - (new_hdr, buf, SZ_SG_IO_HDR); - req_pack_id = new_hdr->pack_id; - kfree(new_hdr); + retval = get_user(req_pack_id, + &((sg_io_hdr_t *)buf->pack_id)); if (retval) { retval = -EFAULT; goto free_old_hdr; -- 2.17.2 (Apple Git-113)