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Commit 35d64801 authored by Eric Biggers's avatar Eric Biggers Committed by Greg Kroah-Hartman
Browse files

vt: vt_ioctl: remove unnecessary console allocation checks 



commit 1aa6e058dd6cd04471b1f21298270014daf48ac9 upstream.

The vc_cons_allocated() checks in vt_ioctl() and vt_compat_ioctl() are
unnecessary because they can only be reached by calling ioctl() on an
open tty, which implies the corresponding virtual console is allocated.

And even if the virtual console *could* be freed concurrently, then
these checks would be broken since they aren't done under console_lock,
and the vc_data is dereferenced before them anyway.

So, remove these unneeded checks to avoid confusion.

Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20200224080326.295046-1-ebiggers@kernel.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 2e1c84e1

drivers/tty/vt/vt_ioctl.c

+2 −19
Original line number Diff line number Diff line
@@ -353,22 +353,13 @@ int vt_ioctl(struct tty_struct *tty, 
{

	struct vc_data *vc = tty->driver_data;

	struct console_font_op op;	/* used in multiple places here */

	unsigned int console;

	unsigned int console = vc->vc_num;

	unsigned char ucval;

	unsigned int uival;

	void __user *up = (void __user *)arg;

	int i, perm;

	int ret = 0;



	console = vc->vc_num;





	if (!vc_cons_allocated(console)) { 	/* impossible? */

		ret = -ENOIOCTLCMD;

		goto out;

	}





	/*

	 * To have permissions to do most of the vt ioctls, we either have

	 * to be the owner of the tty, or have CAP_SYS_TTY_CONFIG.
@@ -1202,18 +1193,10 @@ long vt_compat_ioctl(struct tty_struct *tty, 
{

	struct vc_data *vc = tty->driver_data;

	struct console_font_op op;	/* used in multiple places here */

	unsigned int console;

	void __user *up = (void __user *)arg;

	int perm;

	int ret = 0;



	console = vc->vc_num;



	if (!vc_cons_allocated(console)) { 	/* impossible? */

		ret = -ENOIOCTLCMD;

		goto out;

	}



	/*

	 * To have permissions to do most of the vt ioctls, we either have

	 * to be the owner of the tty, or have CAP_SYS_TTY_CONFIG.
@@ -1273,7 +1256,7 @@ long vt_compat_ioctl(struct tty_struct *tty, 
		arg = (unsigned long)compat_ptr(arg);

		goto fallback;

	}

out:



	return ret;



fallback: