From: Pan Xinhui <xinhuix.pan@intel.com>
Date: Sat, 28 Mar 2015 02:42:56 +0000 (+0800)
Subject: tty/n_gsm.c: fix a memory leak when gsmtty is removed
X-Git-Tag: omap-for-v4.2/wakeirq-drivers~2^2~8^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8f9cfeed3eae86c70d3b04445a6f2036b27b6304;p=pandora-kernel.git

tty/n_gsm.c: fix a memory leak when gsmtty is removed

when gsmtty_remove put dlci, it will cause memory leak if dlci->port's refcount is zero.
So we do the cleanup work in .cleanup callback instead.

dlci will be last put in two call chains.
1) gsmld_close -> gsm_cleanup_mux -> gsm_dlci_release -> dlci_put
2) gsmld_remove -> dlci_put
so there is a race. the memory leak depends on the race.

In call chain 2. we hit the memory leak. below comment tells.

release_tty -> tty_driver_remove_tty -> gsmtty_remove -> dlci_put -> tty_port_destructor (WARN_ON(port->itty) and return directly)
                         |
                tty->port->itty = NULL;
                         |
                tty_kref_put ---> release_one_tty -> gsmtty_cleanup (added by our patch)

So our patch fix the memory leak by doing the cleanup work after tty core did.

Signed-off-by: Pan Xinhui <xinhuix.pan@intel.com>
Fixes: dfabf7ffa30585
Cc: stable <stable@vger.kernel.org> # 3.14+
Acked-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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