Commit 8f9cfeed authored by Pan Xinhui's avatar Pan Xinhui Committed by Greg Kroah-Hartman

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: default avatarPan Xinhui <xinhuix.pan@intel.com>
Fixes: dfabf7ff
Cc: stable <stable@vger.kernel.org> # 3.14+
Acked-by: default avatarJiri Slaby <jslaby@suse.cz>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent ec618478
...@@ -3170,7 +3170,7 @@ static int gsmtty_break_ctl(struct tty_struct *tty, int state) ...@@ -3170,7 +3170,7 @@ static int gsmtty_break_ctl(struct tty_struct *tty, int state)
return gsmtty_modem_update(dlci, encode); return gsmtty_modem_update(dlci, encode);
} }
static void gsmtty_remove(struct tty_driver *driver, struct tty_struct *tty) static void gsmtty_cleanup(struct tty_struct *tty)
{ {
struct gsm_dlci *dlci = tty->driver_data; struct gsm_dlci *dlci = tty->driver_data;
struct gsm_mux *gsm = dlci->gsm; struct gsm_mux *gsm = dlci->gsm;
...@@ -3178,7 +3178,6 @@ static void gsmtty_remove(struct tty_driver *driver, struct tty_struct *tty) ...@@ -3178,7 +3178,6 @@ static void gsmtty_remove(struct tty_driver *driver, struct tty_struct *tty)
dlci_put(dlci); dlci_put(dlci);
dlci_put(gsm->dlci[0]); dlci_put(gsm->dlci[0]);
mux_put(gsm); mux_put(gsm);
driver->ttys[tty->index] = NULL;
} }
/* Virtual ttys for the demux */ /* Virtual ttys for the demux */
...@@ -3199,7 +3198,7 @@ static const struct tty_operations gsmtty_ops = { ...@@ -3199,7 +3198,7 @@ static const struct tty_operations gsmtty_ops = {
.tiocmget = gsmtty_tiocmget, .tiocmget = gsmtty_tiocmget,
.tiocmset = gsmtty_tiocmset, .tiocmset = gsmtty_tiocmset,
.break_ctl = gsmtty_break_ctl, .break_ctl = gsmtty_break_ctl,
.remove = gsmtty_remove, .cleanup = gsmtty_cleanup,
}; };
......
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