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Date: Sun, 19 Feb 2012 22:41:49 +0100 From: Jiri Slaby <jirislaby@...il.com> To: Jiri Slaby <jslaby@...e.cz> CC: gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org, Sasha Levin <levinsasha928@...il.com> Subject: Re: [PATCH 1/1] TTY: fix PTY hangup vs close race On 02/19/2012 10:19 PM, Jiri Slaby wrote: > Commit d3bda5298 (TTY: get rid of BTM around devpts_*) moved > devpts_pty_kill out of BTM, but the BTM was not protecting only > devpts_pty_kill, but also tty->link. Hence move the function back at > this late stage until this gets resolved properly some time later. > > I was confused by tty_vhangup(tty->link) outside BTM. But inside of > tty_vhangup, there is a check for tty == NULL. But we cannot add such > a check here. We have to have the tty and free the devpts node... > > Signed-off-by: Jiri Slaby <jslaby@...e.cz> > Reported-by: Sasha Levin <levinsasha928@...il.com> > --- > > Gee, I messed up Greg's address again... > > drivers/tty/pty.c | 3 ++- > 1 files changed, 2 insertions(+), 1 deletions(-) > > diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c > index fa1bd2e..95037aa 100644 > --- a/drivers/tty/pty.c > +++ b/drivers/tty/pty.c > @@ -54,8 +54,9 @@ static void pty_close(struct tty_struct *tty, struct file *filp) > wake_up_interruptible(&tty->link->write_wait); > if (tty->driver->subtype == PTY_TYPE_MASTER) { > set_bit(TTY_OTHER_CLOSED, &tty->flags); > - tty_unlock(); > + /* BTM protects tty->link here */ > devpts_pty_kill(tty->link); > + tty_unlock(); I'm afraid this won't help. As this is based on an assumption that tty->link is NULL [*] and that is not just true. Greg, please revert commit d3bda5298 completely. [*] Your dump reveals that the code fetches tty->driver_data (mov 0x428(%rdi),%rbx) and traps at a fetch of inode->i_sbm because inode is NULL (mov 0x28(%rbx),%rax). Anyway I'm still interested in the tool you triggered this, because we will need to get rid of BTM eventually. thanks, -- js -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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