The function tty_port_tty_get() gets a reference to the tty. Since the code is not using tty_port_tty_set(), the reference is kept even after closing the tty.
Avoid using tty_port_tty_get() by directly access the tty instance. Since lpuart_start_rx_dma() is called from the .startup() and .set_termios() callback, it is safe to assume the tty instance is valid.
Cc: stable@vger.kernel.org # v4.9+ Fixes: 5887ad43ee02 ("tty: serial: fsl_lpuart: Use cyclic DMA for Rx") Signed-off-by: Stefan Agner stefan@agner.ch --- This fixes a memory leak observable when opening/closing the tty in a loop. This is also reported by kmemleak:
unreferenced object 0xc9d17000 (size 1024): comm "(agetty)", pid 389, jiffies 4294943045 (age 100.670s) hex dump (first 32 bytes): 01 54 00 00 01 00 00 00 00 8c 9b c8 80 58 9b c8 .T...........X.. 48 58 c4 c0 00 00 00 00 00 00 00 00 00 00 00 00 HX.............. backtrace: [<(ptrval)>] kmem_cache_alloc_trace+0x160/0x2b8 [<(ptrval)>] alloc_tty_struct+0x44/0x254 [<(ptrval)>] tty_init_dev+0x44/0x1c8 [<(ptrval)>] tty_open+0x268/0x414 [<(ptrval)>] chrdev_open+0xb4/0x1bc [<(ptrval)>] do_dentry_open+0x1c0/0x388 [<(ptrval)>] vfs_open+0x34/0x38 [<(ptrval)>] path_openat+0x5b0/0x11bc [<(ptrval)>] do_filp_open+0x7c/0xe8 [<(ptrval)>] do_sys_open+0x188/0x20c [<(ptrval)>] sys_openat+0x14/0x18 [<(ptrval)>] ret_fast_syscall+0x0/0x28 [<(ptrval)>] 0xbee0a460 [<(ptrval)>] 0xffffffff
I *think* the statement that accessing tty_struct without using tty_port_tty_get is safe in this case is true. It would be good if somebody with more TTY knowledge could review the change.
-- Stefan
drivers/tty/serial/fsl_lpuart.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c index 51e47a63d61a..3f8d1274fc85 100644 --- a/drivers/tty/serial/fsl_lpuart.c +++ b/drivers/tty/serial/fsl_lpuart.c @@ -979,7 +979,8 @@ static inline int lpuart_start_rx_dma(struct lpuart_port *sport) struct circ_buf *ring = &sport->rx_ring; int ret, nent; int bits, baud; - struct tty_struct *tty = tty_port_tty_get(&sport->port.state->port); + struct tty_port *port = &sport->port.state->port; + struct tty_struct *tty = port->tty; struct ktermios *termios = &tty->termios;
baud = tty_get_baud_rate(tty);