tty: Fix unsafe vt paste_selection()

Convert the tty_buffer_flush() exclusion mechanism to a
public interface - tty_buffer_lock/unlock_exclusive() - and use
the interface to safely write the paste selection to the line
discipline.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 5 insertions, 2 deletions

diff --git a/include/linux/tty.h b/include/linux/tty.h
index 991575fe3451..7a9a3b0a6b5a 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -67,8 +67,8 @@ static inline char *flag_buf_ptr(struct tty_buffer *b, int ofs)
 struct tty_bufhead {
         struct tty_buffer *head;        /* Queue head */
         struct work_struct work;
-        struct mutex flush_mutex;
-        unsigned int flushpending:1;
+        struct mutex       lock;
+        atomic_t           priority;
         struct tty_buffer sentinel;
         struct llist_head free;         /* Free queue head */
         atomic_t           memory_used; /* In-use buffers excluding free list */
diff --git a/include/linux/tty_flip.h b/include/linux/tty_flip.h
index 6944ed2ce692..21ddd7d9ea1f 100644
--- a/include/linux/tty_flip.h
+++ b/include/linux/tty_flip.h
@@ -32,4 +32,7 @@ static inline int tty_insert_flip_string(struct tty_port *port,
         return tty_insert_flip_string_fixed_flag(port, chars, TTY_NORMAL, size);
 }
 
+extern void tty_buffer_lock_exclusive(struct tty_port *port);
+extern void tty_buffer_unlock_exclusive(struct tty_port *port);
+
 #endif /* _LINUX_TTY_FLIP_H */