TTY: fix atime/mtime regression (37b7f3c7) · Commits · 戴 / test

In commit ("TTY: do not update atime/mtime on read/write") we removed timestamps from tty inodes to fix a security issue and waited if something breaks. Well, 'w', the utility to find out logged users and their inactivity time broke. It shows that users are inactive since the time they logged in. To revert to the old behaviour while still preventing attackers to guess the password length, we update the timestamps in one-minute intervals by this patch. Signed-off-by:

Jiri Slaby <jslaby@suse.cz> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

drivers/tty/tty_io.c

+16 −2

Original line number	Diff line number	Diff line
		@@ -941,6 +941,14 @@ void start_tty(struct tty_struct *tty)

		EXPORT_SYMBOL(start_tty);

		static void tty_update_time(struct timespec *time)
		{
		unsigned long sec = get_seconds();
		sec -= sec % 60;
		if ((long)(sec - time->tv_sec) > 0)
		time->tv_sec = sec;
		}

		/**
		* tty_read - read method for tty device files
		* @file: pointer to tty file
		@@ -960,10 +968,11 @@ static ssize_t tty_read(struct file file, char __user buf, size_t count,
		loff_t *ppos)
		{
		int i;
		struct inode *inode = file_inode(file);
		struct tty_struct *tty = file_tty(file);
		struct tty_ldisc *ld;

		if (tty_paranoia_check(tty, file_inode(file), "tty_read"))
		if (tty_paranoia_check(tty, inode, "tty_read"))
		return -EIO;
		if (!tty \|\| (test_bit(TTY_IO_ERROR, &tty->flags)))
		return -EIO;
		@@ -977,6 +986,9 @@ static ssize_t tty_read(struct file file, char __user buf, size_t count,
		i = -EIO;
		tty_ldisc_deref(ld);

		if (i > 0)
		tty_update_time(&inode->i_atime);

		return i;
		}

		@@ -1077,8 +1089,10 @@ static inline ssize_t do_tty_write(
		break;
		cond_resched();
		}
		if (written)
		if (written) {
		tty_update_time(&file_inode(file)->i_mtime);
		ret = written;
		}
		out:
		tty_write_unlock(tty);
		return ret;

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