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Date: Mon, 18 Sep 2023 17:04:38 +0200
From: Sebastian Reichel <sre@...nel.org>
To: Vincent Whitchurch <vincent.whitchurch@...s.com>
Cc: Linus Walleij <linus.walleij@...aro.org>,
Matti Vaittinen <mazziesaccount@...il.com>,
linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
kernel@...s.com
Subject: Re: [PATCH] power: supply: Fix info use-after-free
Hi Vincent,
On Mon, Sep 18, 2023 at 09:33:26AM +0200, Vincent Whitchurch wrote:
> power_supply_uevent() which is called to emit a udev event on device
> deletion attempts to use the info structure which is device-managed and
> has been freed before this point. The use-after-free is triggered since
> commit 699fb50d99039 ("drivers: base: Free devm resources when
> unregistering a device").
>
> Fix this by associating the devm resource with the parent device
> instead, similar to recent fixes done in the input subsystem, such as
> commit dd613a4e45f8 ("HID: uclogic: Correct devm device reference for
> hidinput input_dev").
>
> Note that the power supply subsystem allows drivers to register a device
> without a parent (with a warning), in this case there is still a risk of
> use-after-free since we have no other device to attach the devm to.
Thanks for the bug report with a potential fix already included :)
I think in case of power-supply this might be enough?
diff --git a/drivers/power/supply/power_supply_sysfs.c b/drivers/power/supply/power_supply_sysfs.c
index 06e5b6b0e255..d483a81560ab 100644
--- a/drivers/power/supply/power_supply_sysfs.c
+++ b/drivers/power/supply/power_supply_sysfs.c
@@ -482,6 +482,13 @@ int power_supply_uevent(const struct device *dev, struct kobj_uevent_env *env)
if (ret)
return ret;
+ /*
+ * Kernel generates KOBJ_REMOVE uevent in device removal path, after
+ * resources have been freed. Exit early to avoid use-after-free.
+ */
+ if (psy->removing)
+ return 0;
+
prop_buf = (char *)get_zeroed_page(GFP_KERNEL);
if (!prop_buf)
return -ENOMEM;
That would also cover the no-parent-device part and avoid the
device(s) being queried for data at device removal time, which
wouldn't work if the device removal happens due to a hot-unplug.
-- Sebastian
>
> ==================================================================
> BUG: KASAN: slab-use-after-free in power_supply_battery_info_has_prop (power_supply_core.c:872)
> Read of size 4 at addr 0000000062e59028 by task python3/27
>
> Call Trace:
> power_supply_battery_info_has_prop (power_supply_core.c:872)
> power_supply_uevent (power_supply_sysfs.c:504)
> dev_uevent (drivers/base/core.c:2590)
> kobject_uevent_env (lib/kobject_uevent.c:558)
> kobject_uevent (lib/kobject_uevent.c:643)
> device_del (drivers/base/core.c:3266 drivers/base/core.c:3831)
> device_unregister (drivers/base/core.c:3730 drivers/base/core.c:3854)
> power_supply_unregister (power_supply_core.c:1608)
> devm_power_supply_release (power_supply_core.c:1515)
> release_nodes (drivers/base/devres.c:506)
> devres_release_group (drivers/base/devres.c:669)
> i2c_device_remove (drivers/i2c/i2c-core-base.c:629)
> device_remove (drivers/base/dd.c:570)
> device_release_driver_internal (drivers/base/dd.c:1274 drivers/base/dd.c:1295)
> device_driver_detach (drivers/base/dd.c:1332)
> unbind_store (drivers/base/bus.c:247)
> ...
>
> Allocated by task 27:
> devm_kmalloc (drivers/base/devres.c:119 drivers/base/devres.c:829)
> power_supply_get_battery_info (include/linux/device.h:316 power_supply_core.c:626)
> __power_supply_register (power_supply_core.c:1408)
> devm_power_supply_register (power_supply_core.c:1544)
> bq256xx_probe (bq256xx_charger.c:1539 bq256xx_charger.c:1727) bq256xx_charger
> i2c_device_probe (drivers/i2c/i2c-core-base.c:584)
> really_probe (drivers/base/dd.c:579 drivers/base/dd.c:658)
> __driver_probe_device (drivers/base/dd.c:800)
> device_driver_attach (drivers/base/dd.c:1128)
> bind_store (drivers/base/bus.c:273)
> ...
>
> Freed by task 27:
> kfree (mm/slab_common.c:1073)
> release_nodes (drivers/base/devres.c:503)
> devres_release_all (drivers/base/devres.c:536)
> device_del (drivers/base/core.c:3829)
> device_unregister (drivers/base/core.c:3730 drivers/base/core.c:3854)
> power_supply_unregister (power_supply_core.c:1608)
> devm_power_supply_release (power_supply_core.c:1515)
> release_nodes (drivers/base/devres.c:506)
> devres_release_group (drivers/base/devres.c:669)
> i2c_device_remove (drivers/i2c/i2c-core-base.c:629)
> device_remove (drivers/base/dd.c:570)
> device_release_driver_internal (drivers/base/dd.c:1274 drivers/base/dd.c:1295)
> device_driver_detach (drivers/base/dd.c:1332)
> unbind_store (drivers/base/bus.c:247)
> ...
> ==================================================================
>
> Fixes: 27a2195efa8d ("power: supply: core: auto-exposure of simple-battery data")
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
> ---
> drivers/power/supply/power_supply_core.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
> index 0b69fb7bafd8..2863b0a4dfc7 100644
> --- a/drivers/power/supply/power_supply_core.c
> +++ b/drivers/power/supply/power_supply_core.c
> @@ -573,6 +573,7 @@ EXPORT_SYMBOL_GPL(devm_power_supply_get_by_phandle);
> int power_supply_get_battery_info(struct power_supply *psy,
> struct power_supply_battery_info **info_out)
> {
> + struct device *allocdev = psy->dev.parent ?: &psy->dev;
> struct power_supply_resistance_temp_table *resist_table;
> struct power_supply_battery_info *info;
> struct device_node *battery_np = NULL;
> @@ -623,7 +624,7 @@ int power_supply_get_battery_info(struct power_supply *psy,
> goto out_put_node;
> }
>
> - info = devm_kzalloc(&psy->dev, sizeof(*info), GFP_KERNEL);
> + info = devm_kzalloc(allocdev, sizeof(*info), GFP_KERNEL);
> if (!info) {
> err = -ENOMEM;
> goto out_put_node;
> @@ -776,7 +777,7 @@ int power_supply_get_battery_info(struct power_supply *psy,
> info->ocv_table_size[index] = tab_len;
>
> table = info->ocv_table[index] =
> - devm_kcalloc(&psy->dev, tab_len, sizeof(*table), GFP_KERNEL);
> + devm_kcalloc(allocdev, tab_len, sizeof(*table), GFP_KERNEL);
> if (!info->ocv_table[index]) {
> power_supply_put_battery_info(psy, info);
> err = -ENOMEM;
> @@ -796,7 +797,7 @@ int power_supply_get_battery_info(struct power_supply *psy,
> goto out_ret_pointer;
>
> info->resist_table_size = len / (2 * sizeof(__be32));
> - resist_table = info->resist_table = devm_kcalloc(&psy->dev,
> + resist_table = info->resist_table = devm_kcalloc(allocdev,
> info->resist_table_size,
> sizeof(*resist_table),
> GFP_KERNEL);
> @@ -825,17 +826,18 @@ EXPORT_SYMBOL_GPL(power_supply_get_battery_info);
> void power_supply_put_battery_info(struct power_supply *psy,
> struct power_supply_battery_info *info)
> {
> + struct device *allocdev = psy->dev.parent ?: &psy->dev;
> int i;
>
> for (i = 0; i < POWER_SUPPLY_OCV_TEMP_MAX; i++) {
> if (info->ocv_table[i])
> - devm_kfree(&psy->dev, info->ocv_table[i]);
> + devm_kfree(allocdev, info->ocv_table[i]);
> }
>
> if (info->resist_table)
> - devm_kfree(&psy->dev, info->resist_table);
> + devm_kfree(allocdev, info->resist_table);
>
> - devm_kfree(&psy->dev, info);
> + devm_kfree(allocdev, info);
> }
> EXPORT_SYMBOL_GPL(power_supply_put_battery_info);
>
>
> ---
> base-commit: 0bb80ecc33a8fb5a682236443c1e740d5c917d1d
> change-id: 20230918-power-uaf-6f7f1b585ec5
>
> Best regards,
> --
> Vincent Whitchurch <vincent.whitchurch@...s.com>
>
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