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tty: fix data race in flush_to_ldisc 

flush_to_ldisc reads port->itty and checks that it is not NULL,
concurrently release_tty sets port->itty to NULL. It is possible
that flush_to_ldisc loads port->itty once, ensures that it is
not NULL, but then reloads it again and uses. The second load
can already return NULL, which will cause a crash.

Use READ_ONCE to read port->itty.

The data race was found with KernelThreadSanitizer (KTSAN).

Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Dmitry Vyukov 2015-09-17 17:17:08 +02:00 committed by Greg Kroah-Hartman
parent e81107d4c6
commit 7098296a36
1 changed files with 1 additions and 1 deletions
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2
drivers/tty/tty_buffer.c
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@ -467,7 +467,7 @@ static void flush_to_ldisc(struct work_struct *work)
struct tty_struct *tty;
struct tty_ldisc *disc;
tty = port->itty;
tty = READ_ONCE(port->itty);
if (tty == NULL)
return;