linux-kernel - Re: frequent slab corruption (since a long time)

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Message-Id: <1154626843.23655.101.camel@localhost.localdomain>
Date:	Thu, 03 Aug 2006 18:40:42 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	David Miller <davem@...emloft.net>
Cc:	davej@...hat.com, linux-kernel@...r.kernel.org, jbaron@...hat.com
Subject: Re: frequent slab corruption (since a long time)

Ar Mer, 2006-08-02 am 15:49 -0700, ysgrifennodd David Miller:
> > None of the code manipulating tty->count seems to be under
> > the tty_mutex.  Should it be ?
> > Or is this protected through some other means?
> 
> It is in the primary code paths at least, all callers of init_dev()
> (which increments tty->count) grab the mutex and also release_dev()
> grabs the mutex around tty->count manipulations.

I've been auditing tty code and its joyously bad but only in harmless
places so far except for one.

init_dev (and caller) relies on tty_mutex to ensure that the
driver->ttys list is protected from things going away.

release_mem() removes stuff from the said list and frees memory. It is
not always called under tty_mutex and that appears very dubious to me at
the moment although tty->closing and the BKL *might* be sufficient.

Alan

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