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ipack: ipoctal: fix UAF, null-ptr-deref, and use-after-free in cleanup on remove

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Three issues arise when the device is removed while a tty session is
still active:

1. UAF of struct ipoctal: the remove callback frees ipoctal via
   kfree() while tty ops may still access it.  Fix by introducing
   kref-based lifetime management — kref is taken in install() when
   a tty is opened and released in cleanup() when the tty is finally
   destroyed; remove() uses kref_put() instead of kfree().

2. NULL dereference in ipoctal_write_tty(): __ipoctal_remove()
   frees xmit_buf via tty_port_free_xmit_buf() while a userspace
   process may still hold the tty fd and call write().  Fix by
   checking for NULL xmit_buf in ipoctal_write_tty().

3. UAF in ipoctal_cleanup(): ipack_put_carrier(ipoctal->dev)
   dereferences ipoctal->dev after the ipack_device has been freed
   by ipack_device_del().  Fix by caching ipoctal->carrier_owner
   during probe() and calling module_put() on the cached pointer
   directly in cleanup(), avoiding any access to ipoctal->dev.

Also introduce a "removed" flag in struct ipoctal, set at the start
of __ipoctal_remove(), and checked in every tty op that accesses
hardware resources (port_activate, write_tty, set_termios, hangup,
shutdown).  This prevents page faults when devm_ioremap() regions
are unmapped after remove() returns.

Reported-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
Closes: https://lore.kernel.org/lkml/178144969601.60470.1257088106279546587@gmail.com/
Fixes: 05e5027efc ("Staging: ipack: move out of staging")
Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
Link: https://patch.msgid.link/e3b0a90b07f079c5bcd5ca90d1dd3b79bb29adb5.1782870760.git.xiaopei01@kylinos.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Pei Xiao 2026-07-01 10:01:09 +08:00 committed by Greg Kroah-Hartman
parent de1dea6fad
commit b6b5d64cb1
1 changed files with 52 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

56
drivers/ipack/devices/ipoctal.c
View File

@ -10,6 +10,7 @@
#include <linux/device.h>
#include <linux/module.h>
#include <linux/interrupt.h>
#include <linux/kref.h>
#include <linux/sched.h>
#include <linux/tty.h>
#include <linux/serial.h>
@ -25,6 +26,8 @@
static const struct tty_operations ipoctal_fops;
static void ipoctal_release(struct kref *kref);
struct ipoctal_channel {
struct ipoctal_stats stats;
unsigned int nb_bytes;
@ -49,6 +52,9 @@ struct ipoctal {
struct tty_driver *tty_drv;
u8 __iomem *mem8_space;
u8 __iomem *int_space;
struct kref kref;
struct module *carrier_owner;
bool removed;
};
static inline struct ipoctal *chan_to_ipoctal(struct ipoctal_channel *chan,
@ -70,8 +76,14 @@ static void ipoctal_reset_channel(struct ipoctal_channel *channel)
static int ipoctal_port_activate(struct tty_port *port, struct tty_struct *tty)
{
struct ipoctal_channel *channel;
struct ipoctal *ipoctal;
channel = dev_get_drvdata(tty->dev);
ipoctal = chan_to_ipoctal(channel, tty->index);
if (ipoctal->removed)
return -ENODEV;
/*
* Enable RX. TX will be enabled when
@ -95,6 +107,7 @@ static int ipoctal_install(struct tty_driver *driver, struct tty_struct *tty)
if (res)
goto err_put_carrier;
kref_get(&ipoctal->kref);
tty->driver_data = channel;
return 0;
@ -460,8 +473,13 @@ static ssize_t ipoctal_write_tty(struct tty_struct *tty, const u8 *buf,
size_t count)
{
struct ipoctal_channel *channel = tty->driver_data;
struct ipoctal *ipoctal = chan_to_ipoctal(channel, tty->index);
size_t char_copied;
if (ipoctal->removed || !channel->tty_port.xmit_buf)
return 0;
char_copied = ipoctal_copy_write_buffer(channel, buf, count);
/* As the IP-OCTAL 485 only supports half duplex, do it manually */
@ -501,8 +519,13 @@ static void ipoctal_set_termios(struct tty_struct *tty,
unsigned char mr2 = 0;
unsigned char csr = 0;
struct ipoctal_channel *channel = tty->driver_data;
struct ipoctal *ipoctal = chan_to_ipoctal(channel, tty->index);
speed_t baud;
if (ipoctal->removed)
return;
cflag = tty->termios.c_cflag;
/* Disable and reset everything before change the setup */
@ -631,10 +654,16 @@ static void ipoctal_hangup(struct tty_struct *tty)
{
unsigned long flags;
struct ipoctal_channel *channel = tty->driver_data;
struct ipoctal *ipoctal;
if (channel == NULL)
return;
ipoctal = chan_to_ipoctal(channel, tty->index);
if (ipoctal->removed)
return;
spin_lock_irqsave(&channel->lock, flags);
channel->nb_bytes = 0;
channel->pointer_read = 0;
@ -651,10 +680,16 @@ static void ipoctal_hangup(struct tty_struct *tty)
static void ipoctal_shutdown(struct tty_struct *tty)
{
struct ipoctal_channel *channel = tty->driver_data;
struct ipoctal *ipoctal;
if (channel == NULL)
return;
ipoctal = chan_to_ipoctal(channel, tty->index);
if (ipoctal->removed)
return;
ipoctal_reset_channel(channel);
tty_port_set_initialized(&channel->tty_port, false);
}
@ -664,8 +699,9 @@ static void ipoctal_cleanup(struct tty_struct *tty)
struct ipoctal_channel *channel = tty->driver_data;
struct ipoctal *ipoctal = chan_to_ipoctal(channel, tty->index);
/* release the carrier driver */
ipack_put_carrier(ipoctal->dev);
/* release the carrier driver via cached owner */
module_put(ipoctal->carrier_owner);
kref_put(&ipoctal->kref, ipoctal_release);
}
static const struct tty_operations ipoctal_fops = {
@ -683,6 +719,13 @@ static const struct tty_operations ipoctal_fops = {
.cleanup = ipoctal_cleanup,
};
static void ipoctal_release(struct kref *kref)
{
struct ipoctal *ipoctal = container_of(kref, struct ipoctal, kref);
kfree(ipoctal);
}
static int ipoctal_probe(struct ipack_device *dev)
{
int res;
@ -692,7 +735,10 @@ static int ipoctal_probe(struct ipack_device *dev)
if (ipoctal == NULL)
return -ENOMEM;
kref_init(&ipoctal->kref);
ipoctal->dev = dev;
ipoctal->carrier_owner = dev->bus->owner;
res = ipoctal_inst_slot(ipoctal, dev->bus->bus_nr, dev->slot);
if (res)
goto out_uninst;
@ -701,7 +747,7 @@ static int ipoctal_probe(struct ipack_device *dev)
return 0;
out_uninst:
kfree(ipoctal);
kref_put(&ipoctal->kref, ipoctal_release);
return res;
}
@ -709,6 +755,8 @@ static void __ipoctal_remove(struct ipoctal *ipoctal)
{
int i;
ipoctal->removed = true;
ipoctal->dev->bus->ops->free_irq(ipoctal->dev);
for (i = 0; i < NR_CHANNELS; i++) {
@ -725,7 +773,7 @@ static void __ipoctal_remove(struct ipoctal *ipoctal)
tty_unregister_driver(ipoctal->tty_drv);
kfree(ipoctal->tty_drv->name);
tty_driver_kref_put(ipoctal->tty_drv);
kfree(ipoctal);
kref_put(&ipoctal->kref, ipoctal_release);
}
static void ipoctal_remove(struct ipack_device *idev)