[PATCH RESEND v2 20/23] platform/x86: thinkpad_acpi: let procfs copy in writes

[Christian Brauner]

Implement ->proc_write_buf() so procfs copies in what is written to
/proc/acpi/ibm/* before it pins the entry, and hand that copy to
->write(). procfs already rejects writes larger than PAGE_SIZE - 1
bytes.

Signed-off-by: Christian Brauner (Amutable) <brauner at kernel.org>
---
 drivers/platform/x86/lenovo/thinkpad_acpi.c | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/drivers/platform/x86/lenovo/thinkpad_acpi.c b/drivers/platform/x86/lenovo/thinkpad_acpi.c
index 2ee208c82801..8287b36bd90d 100644
--- a/drivers/platform/x86/lenovo/thinkpad_acpi.c
+++ b/drivers/platform/x86/lenovo/thinkpad_acpi.c
@@ -882,7 +882,7 @@ static int dispatch_proc_show(struct seq_file *m, void *v)
 }
 
 static ssize_t dispatch_proc_write(struct file *file,
-			const char __user *userbuf,
+			char *buf,
 			size_t count, loff_t *pos)
 {
 	struct ibm_struct *ibm = pde_data(file_inode(file));
@@ -890,14 +890,8 @@ static ssize_t dispatch_proc_write(struct file *file,
 
 	if (!ibm || !ibm->write)
 		return -EINVAL;
-	if (count > PAGE_SIZE - 1)
-		return -EINVAL;
-
-	char *kernbuf __free(kfree) = memdup_user_nul(userbuf, count);
-	if (IS_ERR(kernbuf))
-		return PTR_ERR(kernbuf);
 
-	ret = ibm->write(kernbuf);
+	ret = ibm->write(buf);
 	if (ret)
 		return ret;
 
@@ -906,7 +900,7 @@ static ssize_t dispatch_proc_write(struct file *file,
 
 static const struct proc_ops dispatch_proc_ops = {
 	.proc_show	= dispatch_proc_show,
-	.proc_write	= dispatch_proc_write,
+	.proc_write_buf	= dispatch_proc_write,
 };
 
 /****************************************************************************

-- 
2.53.0