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/n_null.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+) create mode 100644 drivers/tty/n_null.c (limited to 'drivers/tty/n_null.c') diff --git a/drivers/tty/n_null.c b/drivers/tty/n_null.c new file mode 100644 index 000000000..5a429d923 --- /dev/null +++ b/drivers/tty/n_null.c @@ -0,0 +1,50 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include + +/* + * n_null.c - Null line discipline used in the failure path + * + * Copyright (C) Intel 2017 + */ + +static ssize_t n_null_read(struct tty_struct *tty, struct file *file, u8 *buf, + size_t nr, void **cookie, unsigned long offset) +{ + return -EOPNOTSUPP; +} + +static ssize_t n_null_write(struct tty_struct *tty, struct file *file, + const u8 *buf, size_t nr) +{ + return -EOPNOTSUPP; +} + +static struct tty_ldisc_ops null_ldisc = { + .owner = THIS_MODULE, + .num = N_NULL, + .name = "n_null", + .read = n_null_read, + .write = n_null_write, +}; + +static int __init n_null_init(void) +{ + BUG_ON(tty_register_ldisc(&null_ldisc)); + return 0; +} + +static void __exit n_null_exit(void) +{ + tty_unregister_ldisc(&null_ldisc); +} + +module_init(n_null_init); +module_exit(n_null_exit); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Alan Cox"); +MODULE_ALIAS_LDISC(N_NULL); +MODULE_DESCRIPTION("Null ldisc driver"); -- cgit v1.3.1