tty: Fix termios tty window resize race with pty/tty pair (a152db71) · Commits · 戴 / test

Kanru Chen posted a patch versus the old code which deals with the case where you resize the pty side of a pty/tty pair. In that situation the termios data is updated for both pty and tty but the locks are not held for the right side. This implements the fix differently against the updated tty code. Patch by self but the hard bit (noticing and fixing the bug) is thanks to Kanru Chen. Signed-off-by:

Alan Cox <alan@redhat.com> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

drivers/char/tty_io.c

+4 −3

Original line number	Diff line number	Diff line
		@@ -2498,7 +2498,7 @@ static int tiocgwinsz(struct tty_struct tty, struct winsize __user arg)
		/**
		* tty_do_resize - resize event
		* @tty: tty being resized
		* @real_tty: real tty (if using a pty/tty pair)
		* @real_tty: real tty (not the same as tty if using a pty/tty pair)
		* @rows: rows (character)
		* @cols: cols (character)
		*
		@@ -2512,7 +2512,8 @@ int tty_do_resize(struct tty_struct tty, struct tty_struct real_tty,
		struct pid pgrp, rpgrp;
		unsigned long flags;

		mutex_lock(&tty->termios_mutex);
		/* For a PTY we need to lock the tty side */
		mutex_lock(&real_tty->termios_mutex);
		if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
		goto done;
		/* Get the PID values and reference them so we can
		@@ -2533,7 +2534,7 @@ int tty_do_resize(struct tty_struct tty, struct tty_struct real_tty,
		tty->winsize = *ws;
		real_tty->winsize = *ws;
		done:
		mutex_unlock(&tty->termios_mutex);
		mutex_unlock(&real_tty->termios_mutex);
		return 0;
		}

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