On 20. 05. 20, 8:47, Raghavendra Rao Ananta wrote:
Potentially, hvc_open() can be called in parallel when two tasks calls open() on /dev/hvcX. In such a scenario, if the hp->ops->notifier_add() callback in the function fails, where it sets the tty->driver_data to NULL, the parallel hvc_open() can see this NULL and cause a memory abort. Hence, do a NULL check at the beginning, before proceeding ahead.
The issue can be easily reproduced by launching two tasks simultaneously that does an open() call on /dev/hvcX. For example: $ cat /dev/hvc0 & cat /dev/hvc0 &
Cc: stable@vger.kernel.org Signed-off-by: Raghavendra Rao Ananta rananta@codeaurora.org
drivers/tty/hvc/hvc_console.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c index 436cc51c92c3..80709f754cc8 100644 --- a/drivers/tty/hvc/hvc_console.c +++ b/drivers/tty/hvc/hvc_console.c @@ -350,6 +350,9 @@ static int hvc_open(struct tty_struct *tty, struct file * filp) unsigned long flags; int rc = 0;
- if (!hp)
return -ENODEV;
This is still not fixing the bug properly. See: https://lore.kernel.org/linuxppc-dev/0f7791f5-0a53-59f6-7277-247a789f30c2@su...
In particular, the paragraph starting "IOW".
thanks,