Messages in this thread Patch in this message | | | Date | Wed, 25 Mar 2015 15:05:33 +0800 | From | Pan Xinhui <> | Subject | [PATCH v2] tty/n_gsm.c: fix a memory leak when gsmtty is removed |
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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. bellow 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 (now we do the cleanup work here.) So our patch fix it by doing the cleanup work after tty core did.
Signed-off-by: xinhui.pan <xinhuix.pan@intel.com> --- drivers/tty/n_gsm.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index c434376..bce16e4 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -3170,7 +3170,7 @@ static int gsmtty_break_ctl(struct tty_struct *tty, int state) 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_mux *gsm = dlci->gsm; @@ -3178,7 +3178,6 @@ static void gsmtty_remove(struct tty_driver *driver, struct tty_struct *tty) dlci_put(dlci); dlci_put(gsm->dlci[0]); mux_put(gsm); - driver->ttys[tty->index] = NULL; } /* Virtual ttys for the demux */ @@ -3199,7 +3198,7 @@ static const struct tty_operations gsmtty_ops = { .tiocmget = gsmtty_tiocmget, .tiocmset = gsmtty_tiocmset, .break_ctl = gsmtty_break_ctl, - .remove = gsmtty_remove, + .cleanup = gsmtty_cleanup, }; -- 1.9.1
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