Merge tag 'tty-4.18-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

Pull tty/serial fixes from Greg KH:
"Here are five fixes for the tty core and some serial drivers.

The tty core ones fix some security and other issues reported by the
syzbot that I have taken too long in responding to (sorry Tetsuo!).

The 8350 serial driver fix resolves an issue of devices that used to
work properly stopping working as they shouldn't have been added to a
blacklist.

All of these have been in linux-next for a few days with no reported
issues"

* tag 'tty-4.18-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
vt: prevent leaking uninitialized data to userspace via /dev/vcs*
serdev: fix memleak on module unload
serial: 8250_pci: Remove stalled entries in blacklist
n_tty: Access echo_* variables carefully.
n_tty: Fix stall at n_tty_receive_char_special().

drivers/tty/n_tty.c

···
 	struct mutex output_lock;
 };
 
+#define MASK(x) ((x) & (N_TTY_BUF_SIZE - 1))
+
 static inline size_t read_cnt(struct n_tty_data *ldata)
 {
 	return ldata->read_head - ldata->read_tail;
···
 
 static inline unsigned char echo_buf(struct n_tty_data *ldata, size_t i)
 {
+	smp_rmb(); /* Matches smp_wmb() in add_echo_byte(). */
 	return ldata->echo_buf[i & (N_TTY_BUF_SIZE - 1)];
 }
 
···
 static void reset_buffer_flags(struct n_tty_data *ldata)
 {
 	ldata->read_head = ldata->canon_head = ldata->read_tail = 0;
-	ldata->echo_head = ldata->echo_tail = ldata->echo_commit = 0;
 	ldata->commit_head = 0;
-	ldata->echo_mark = 0;
 	ldata->line_start = 0;
 
 	ldata->erasing = 0;
···
 	old_space = space = tty_write_room(tty);
 
 	tail = ldata->echo_tail;
-	while (ldata->echo_commit != tail) {
+	while (MASK(ldata->echo_commit) != MASK(tail)) {
 		c = echo_buf(ldata, tail);
 		if (c == ECHO_OP_START) {
 			unsigned char op;
 			int no_space_left = 0;
 
+			/*
+			 * Since add_echo_byte() is called without holding
+			 * output_lock, we might see only portion of multi-byte
+			 * operation.
+			 */
+			if (MASK(ldata->echo_commit) == MASK(tail + 1))
+				goto not_yet_stored;
 			/*
 			 * If the buffer byte is the start of a multi-byte
 			 * operation, get the next byte, which is either the
···
 				unsigned int num_chars, num_bs;
 
 			case ECHO_OP_ERASE_TAB:
+				if (MASK(ldata->echo_commit) == MASK(tail + 2))
+					goto not_yet_stored;
 				num_chars = echo_buf(ldata, tail + 2);
 
 				/*
···
 	/* If the echo buffer is nearly full (so that the possibility exists
 	 * of echo overrun before the next commit), then discard enough
 	 * data at the tail to prevent a subsequent overrun */
-	while (ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
+	while (ldata->echo_commit > tail &&
+	       ldata->echo_commit - tail >= ECHO_DISCARD_WATERMARK) {
 		if (echo_buf(ldata, tail) == ECHO_OP_START) {
 			if (echo_buf(ldata, tail + 1) == ECHO_OP_ERASE_TAB)
 				tail += 3;
···
 			tail++;
 	}
 
+ not_yet_stored:
 	ldata->echo_tail = tail;
 	return old_space - space;
 }
···
 	size_t nr, old, echoed;
 	size_t head;
 
+	mutex_lock(&ldata->output_lock);
 	head = ldata->echo_head;
 	ldata->echo_mark = head;
 	old = ldata->echo_commit - ldata->echo_tail;
···
 	 * is over the threshold (and try again each time another
 	 * block is accumulated) */
 	nr = head - ldata->echo_tail;
-	if (nr < ECHO_COMMIT_WATERMARK || (nr % ECHO_BLOCK > old % ECHO_BLOCK))
+	if (nr < ECHO_COMMIT_WATERMARK ||
+	    (nr % ECHO_BLOCK > old % ECHO_BLOCK)) {
+		mutex_unlock(&ldata->output_lock);
 		return;
+	}
 
-	mutex_lock(&ldata->output_lock);
 	ldata->echo_commit = head;
 	echoed = __process_echoes(tty);
 	mutex_unlock(&ldata->output_lock);
···
 
 static inline void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
 {
-	*echo_buf_addr(ldata, ldata->echo_head++) = c;
+	*echo_buf_addr(ldata, ldata->echo_head) = c;
+	smp_wmb(); /* Matches smp_rmb() in echo_buf(). */
+	ldata->echo_head++;
 }
 
 /**
···
 	}
 
 	seen_alnums = 0;
-	while (ldata->read_head != ldata->canon_head) {
+	while (MASK(ldata->read_head) != MASK(ldata->canon_head)) {
 		head = ldata->read_head;
 
 		/* erase a single possibly multibyte character */
 		do {
 			head--;
 			c = read_buf(ldata, head);
-		} while (is_continuation(c, tty) && head != ldata->canon_head);
+		} while (is_continuation(c, tty) &&
+			 MASK(head) != MASK(ldata->canon_head));
 
 		/* do not partially erase */
 		if (is_continuation(c, tty))
···
 				 * This info is used to go back the correct
 				 * number of columns.
 				 */
-				while (tail != ldata->canon_head) {
+				while (MASK(tail) != MASK(ldata->canon_head)) {
 					tail--;
 					c = read_buf(ldata, tail);
 					if (c == '\t') {
···
 			finish_erasing(ldata);
 			echo_char(c, tty);
 			echo_char_raw('\n', ldata);
-			while (tail != ldata->read_head) {
+			while (MASK(tail) != MASK(ldata->read_head)) {
 				echo_char(read_buf(ldata, tail), tty);
 				tail++;
 			}
···
 	struct n_tty_data *ldata;
 
 	/* Currently a malloc failure here can panic */
-	ldata = vmalloc(sizeof(*ldata));
+	ldata = vzalloc(sizeof(*ldata));
 	if (!ldata)
-		goto err;
+		return -ENOMEM;
 
 	ldata->overrun_time = jiffies;
 	mutex_init(&ldata->atomic_read_lock);
 	mutex_init(&ldata->output_lock);
 
 	tty->disc_data = ldata;
-	reset_buffer_flags(tty->disc_data);
-	ldata->column = 0;
-	ldata->canon_column = 0;
-	ldata->num_overrun = 0;
-	ldata->no_room = 0;
-	ldata->lnext = 0;
 	tty->closing = 0;
 	/* indicate buffer work may resume */
 	clear_bit(TTY_LDISC_HALTED, &tty->flags);
 	n_tty_set_termios(tty, NULL);
 	tty_unthrottle(tty);
-
 	return 0;
-err:
-	return -ENOMEM;
 }
 
 static inline int input_available_p(struct tty_struct *tty, int poll)
···
 	tail = ldata->read_tail;
 	nr = head - tail;
 	/* Skip EOF-chars.. */
-	while (head != tail) {
+	while (MASK(head) != MASK(tail)) {
 		if (test_bit(tail & (N_TTY_BUF_SIZE - 1), ldata->read_flags) &&
 		    read_buf(ldata, tail) == __DISABLED_CHAR)
 			nr--;

drivers/tty/serdev/core.c

···
 static void __exit serdev_exit(void)
 {
 	bus_unregister(&serdev_bus_type);
+	ida_destroy(&ctrl_ida);
 }
 module_exit(serdev_exit);
 

drivers/tty/serial/8250/8250_pci.c

···
 	/* multi-io cards handled by parport_serial */
 	{ PCI_DEVICE(0x4348, 0x7053), }, /* WCH CH353 2S1P */
 	{ PCI_DEVICE(0x4348, 0x5053), }, /* WCH CH353 1S1P */
-	{ PCI_DEVICE(0x4348, 0x7173), }, /* WCH CH355 4S */
 	{ PCI_DEVICE(0x1c00, 0x3250), }, /* WCH CH382 2S1P */
-	{ PCI_DEVICE(0x1c00, 0x3470), }, /* WCH CH384 4S */
 
 	/* Moxa Smartio MUE boards handled by 8250_moxa */
 	{ PCI_VDEVICE(MOXA, 0x1024), },

drivers/tty/vt/vt.c

···
 	if (!*vc->vc_uni_pagedir_loc)
 		con_set_default_unimap(vc);
 
-	vc->vc_screenbuf = kmalloc(vc->vc_screenbuf_size, GFP_KERNEL);
+	vc->vc_screenbuf = kzalloc(vc->vc_screenbuf_size, GFP_KERNEL);
 	if (!vc->vc_screenbuf)
 		goto err_free;
 
···
 
 	if (new_screen_size > (4 << 20))
 		return -EINVAL;
-	newscreen = kmalloc(new_screen_size, GFP_USER);
+	newscreen = kzalloc(new_screen_size, GFP_USER);
 	if (!newscreen)
 		return -ENOMEM;