[PATCH v2] crypto: hisilicon - allow smaller reads in debugfs

From: Dan Carpenter <dan.carpenter@oracle.com>
To: Zhou Wang <wangzhou1@hisilicon.com>, Shukun Tan <tanshukun1@huawei.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>,
	"David S. Miller" <davem@davemloft.net>,
	linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org,
	kernel-janitors@vger.kernel.org
Subject: [PATCH v2] crypto: hisilicon - allow smaller reads in debugfs
Date: Tue, 2 Jun 2020 16:54:09 +0300	[thread overview]
Message-ID: <20200602135409.GA59808@mwanda> (raw)

Originally this code rejected any read less than 256 bytes.  There
is no need for this artificial limit.  We should just use the normal
helper functions to read a string from the kernel.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
v2: Use simple_read_from_buffer().  The v1 was slightly half arsed
because I left the original check for:

	if (*pos)
		return 0;

So it could result in partial reads.  The new code means that if you
want to read the buffer one byte at a time, that's fine or if you want
to read it in one 256 byte chunk that's also fine.  Plus it deletes 21
lines of code and is a lot cleaner.

 drivers/crypto/hisilicon/qm.c | 33 ++++++---------------------------
 1 file changed, 6 insertions(+), 27 deletions(-)

diff --git a/drivers/crypto/hisilicon/qm.c b/drivers/crypto/hisilicon/qm.c
index 9bb263cec6c30..13ccb9e29a2e1 100644
--- a/drivers/crypto/hisilicon/qm.c
+++ b/drivers/crypto/hisilicon/qm.c
@@ -1064,19 +1064,10 @@ static ssize_t qm_cmd_read(struct file *filp, char __user *buffer,
 	char buf[QM_DBG_READ_LEN];
 	int len;
 
-	if (*pos)
-		return 0;
-
-	if (count < QM_DBG_READ_LEN)
-		return -ENOSPC;
+	len = scnprintf(buf, QM_DBG_READ_LEN, "%s\n",
+			"Please echo help to cmd to get help information");
 
-	len = snprintf(buf, QM_DBG_READ_LEN, "%s\n",
-		       "Please echo help to cmd to get help information");
-
-	if (copy_to_user(buffer, buf, len))
-		return -EFAULT;
-
-	return (*pos = len);
+	return simple_read_from_buffer(buffer, count, pos, buf, len);
 }
 
 static void *qm_ctx_alloc(struct hisi_qm *qm, size_t ctx_size,
@@ -2691,24 +2682,12 @@ static ssize_t qm_status_read(struct file *filp, char __user *buffer,
 {
 	struct hisi_qm *qm = filp->private_data;
 	char buf[QM_DBG_READ_LEN];
-	int val, cp_len, len;
-
-	if (*pos)
-		return 0;
-
-	if (count < QM_DBG_READ_LEN)
-		return -ENOSPC;
+	int val, len;
 
 	val = atomic_read(&qm->status.flags);
-	len = snprintf(buf, QM_DBG_READ_LEN, "%s\n", qm_s[val]);
-	if (!len)
-		return -EFAULT;
-
-	cp_len = copy_to_user(buffer, buf, len);
-	if (cp_len)
-		return -EFAULT;
+	len = scnprintf(buf, QM_DBG_READ_LEN, "%s\n", qm_s[val]);
 
-	return (*pos = len);
+	return simple_read_from_buffer(buffer, count, pos, buf, len);
 }
 
 static const struct file_operations qm_status_fops = {
-- 
2.26.2

