vt: vt_ioctl: remove unnecessary console allocation checks (1aa6e058) · Commits · 戴 / test

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:

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

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/vt/vt_ioctl.c

+1 −15

Original line number	Diff line number	Diff line
		@@ -350,22 +350,13 @@ 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.
		@@ -1195,14 +1186,9 @@ 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 = vc->vc_num;
		void __user *up = compat_ptr(arg);
		int perm;


		if (!vc_cons_allocated(console)) /* impossible? */
		return -ENOIOCTLCMD;

		/*
		* 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.

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