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From: "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
To: gregkh@linuxfoundation.org
Cc: linux-serial@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	"Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Subject: [PATCH 06/45] tty: vt: push console lock from tioclinux() down to 2 functions
Date: Thu, 18 Jan 2024 08:57:17 +0100
Message-ID: <20240118075756.10541-7-jirislaby@kernel.org>
In-Reply-To: <20240118075756.10541-1-jirislaby@kernel.org>
References: <20240118075756.10541-1-jirislaby@kernel.org>
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Avoid costly user copies under the console lock. So push the lock down
from tioclinux() to sel_loadlut() and set_vesa_blanking().

It is now obvious what is actually protected.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
---
 drivers/tty/vt/selection.c | 11 +++++++++--
 drivers/tty/vt/vt.c        | 13 +++++--------
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/tty/vt/selection.c b/drivers/tty/vt/selection.c
index e172ede235a0..91d789c025c6 100644
--- a/drivers/tty/vt/selection.c
+++ b/drivers/tty/vt/selection.c
@@ -113,15 +113,22 @@ static inline int inword(const u32 c)
  *	sel_loadlut()		-	load the LUT table
  *	@lut: user table
  *
- *	Load the LUT table from user space. The caller must hold the console
- *	lock. Make a temporary copy so a partial update doesn't make a mess.
+ *	Load the LUT table from user space. Make a temporary copy so a partial
+ *	update doesn't make a mess.
+ *
+ *	Locking: The console lock is acquired.
  */
 int sel_loadlut(u32 __user *lut)
 {
 	u32 tmplut[ARRAY_SIZE(inwordLut)];
+
 	if (copy_from_user(tmplut, lut, sizeof(inwordLut)))
 		return -EFAULT;
+
+	console_lock();
 	memcpy(inwordLut, tmplut, sizeof(inwordLut));
+	console_unlock();
+
 	return 0;
 }
 
diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 079dbff562fd..3a6f60ad2224 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -3162,10 +3162,7 @@ int tioclinux(struct tty_struct *tty, unsigned long arg)
 	case TIOCL_SELLOADLUT:
 		if (!capable(CAP_SYS_ADMIN))
 			return -EPERM;
-		console_lock();
-		ret = sel_loadlut(param_aligned32);
-		console_unlock();
-		break;
+		return sel_loadlut(param_aligned32);
 	case TIOCL_GETSHIFTSTATE:
 		/*
 		 * Make it possible to react to Shift+Mousebutton. Note that
@@ -3181,10 +3178,7 @@ int tioclinux(struct tty_struct *tty, unsigned long arg)
 		console_unlock();
 		return put_user(data, p);
 	case TIOCL_SETVESABLANK:
-		console_lock();
-		ret = set_vesa_blanking(param);
-		console_unlock();
-		break;
+		return set_vesa_blanking(param);
 	case TIOCL_GETKMSGREDIRECT:
 		data = vt_get_kmsg_redirect();
 		return put_user(data, p);
@@ -4270,7 +4264,10 @@ static int set_vesa_blanking(u8 __user *mode_user)
 	if (get_user(mode, mode_user))
 		return -EFAULT;
 
+	console_lock();
 	vesa_blank_mode = (mode < 4) ? mode : 0;
+	console_unlock();
+
 	return 0;
 }
 
-- 
2.43.0