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Date: Mon, 20 Feb 2012 12:20:13 +0200 From: Sasha Levin <levinsasha928@...il.com> To: Jiri Slaby <jirislaby@...il.com> Cc: Jiri Slaby <jslaby@...e.cz>, gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 1/1] TTY: fix PTY hangup vs close race On Sun, Feb 19, 2012 at 11:41 PM, Jiri Slaby <jirislaby@...il.com> wrote: > 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). It actually looks even more complex than that. I reverted the patch above, but still got the error. A quick bisection pointed me to a50f724a432997321cabb6c9e665c28e34850f78. Looks like reverting both actually solves the problem. Reverting just one of them doesn't. -- 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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