From: Stefan Agner <stefan@agner.ch>
To: gregkh@linuxfoundation.org
Cc: jslaby@suse.com, peter@hurleysoftware.com,
linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
Stefan Agner <stefan@agner.ch>,
stable@vger.kernel.org
Subject: [PATCH] tty: serial: lpuart: avoid leaking struct tty_struct
Date: Tue, 28 Aug 2018 12:44:24 +0200 [thread overview]
Message-ID: <20180828104424.19860-1-stefan@agner.ch> (raw)
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.
reply other threads:[~2018-08-28 10:44 UTC|newest]
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