From e873c74132f0c5f1452816cd9bb26208f0bba1e1 Mon Sep 17 00:00:00 2001 From: Shivank Garg Date: Sat, 22 Aug 2026 19:22:05 +0000 Subject: dmaengine: fix use-after-free in dma_chan_put() and dma_release_channel() When dma_device_put() drops the last reference on chan->device->ref, dma_device_release() runs and may free the dma_device along with its channels. dma_chan_put() then still reads chan->device->owner via dma_chan_to_owner() for the trailing module_put(). KASAN catches it: slab-use-after-free in dma_chan_put+0x3e6/0x4c0 Read of size 8 by task insmod/6319 Freed by task 6319: kfree+0x225/0x470 dma_chan_put+0x395/0x4c0 dmaengine_put+0xf8/0x160 Cache the module owner in dma_chan_put() before the put so the trailing module_put() does not need chan->device. Fixes: 8ad342a86359 ("dmaengine: Add reference counting to dma_device struct") Suggested-by: Sashiko Link: https://sashiko.dev/#/patchset/20260518-dmaengine-kref-fix-v1-1-4d6125048fb7@amd.com Reviewed-by: Frank Li Reviewed-by: Logan Gunthorpe Signed-off-by: Shivank Garg Link: https://patch.msgid.link/20260822-dmaengine-kref-fix-v5-3-d4a4ee47d927@amd.com Signed-off-by: Vinod Koul --- drivers/tty/ttynull.c | 110 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 110 insertions(+) create mode 100644 drivers/tty/ttynull.c (limited to 'drivers/tty/ttynull.c') diff --git a/drivers/tty/ttynull.c b/drivers/tty/ttynull.c new file mode 100644 index 000000000..6b2f7208b --- /dev/null +++ b/drivers/tty/ttynull.c @@ -0,0 +1,110 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2019 Axis Communications AB + * + * Based on ttyprintk.c: + * Copyright (C) 2010 Samo Pogacnik + */ + +#include +#include +#include + +static const struct tty_port_operations ttynull_port_ops; +static struct tty_driver *ttynull_driver; +static struct tty_port ttynull_port; + +static int ttynull_open(struct tty_struct *tty, struct file *filp) +{ + return tty_port_open(&ttynull_port, tty, filp); +} + +static void ttynull_close(struct tty_struct *tty, struct file *filp) +{ + tty_port_close(&ttynull_port, tty, filp); +} + +static void ttynull_hangup(struct tty_struct *tty) +{ + tty_port_hangup(&ttynull_port); +} + +static ssize_t ttynull_write(struct tty_struct *tty, const u8 *buf, + size_t count) +{ + return count; +} + +static unsigned int ttynull_write_room(struct tty_struct *tty) +{ + return 65536; +} + +static const struct tty_operations ttynull_ops = { + .open = ttynull_open, + .close = ttynull_close, + .hangup = ttynull_hangup, + .write = ttynull_write, + .write_room = ttynull_write_room, +}; + +static struct tty_driver *ttynull_device(struct console *c, int *index) +{ + *index = 0; + return ttynull_driver; +} + +static struct console ttynull_console = { + .name = "ttynull", + .device = ttynull_device, +}; + +static int __init ttynull_init(void) +{ + struct tty_driver *driver; + int ret; + + driver = tty_alloc_driver(1, + TTY_DRIVER_RESET_TERMIOS | + TTY_DRIVER_REAL_RAW | + TTY_DRIVER_UNNUMBERED_NODE); + if (IS_ERR(driver)) + return PTR_ERR(driver); + + tty_port_init(&ttynull_port); + ttynull_port.ops = &ttynull_port_ops; + + driver->driver_name = "ttynull"; + driver->name = "ttynull"; + driver->type = TTY_DRIVER_TYPE_CONSOLE; + driver->init_termios = tty_std_termios; + driver->init_termios.c_oflag = OPOST | OCRNL | ONOCR | ONLRET; + tty_set_operations(driver, &ttynull_ops); + tty_port_link_device(&ttynull_port, driver, 0); + + ret = tty_register_driver(driver); + if (ret < 0) { + tty_driver_kref_put(driver); + tty_port_destroy(&ttynull_port); + return ret; + } + + ttynull_driver = driver; + register_console(&ttynull_console); + + return 0; +} + +static void __exit ttynull_exit(void) +{ + unregister_console(&ttynull_console); + tty_unregister_driver(ttynull_driver); + tty_driver_kref_put(ttynull_driver); + tty_port_destroy(&ttynull_port); +} + +module_init(ttynull_init); +module_exit(ttynull_exit); + +MODULE_DESCRIPTION("NULL TTY driver"); +MODULE_LICENSE("GPL v2"); -- cgit v1.3.1