The cros_ec_chardev driver provides a character device interface to the
ChromeOS EC. A file handle to this device can remain open in userspace
even if the underlying EC device is removed.
This creates a classic use-after-free vulnerability. Any file operation
(ioctl, release, etc.) on the open handle after the EC device has gone
would access a stale pointer, leading to a system crash.
To prevent this, leverage the ref_proxy library and convert
cros_ec_chardev to a resource consumer of cros_ec_device.
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
---
drivers/platform/chrome/cros_ec_chardev.c | 125 +++++++++++++++-------
1 file changed, 85 insertions(+), 40 deletions(-)
diff --git a/drivers/platform/chrome/cros_ec_chardev.c b/drivers/platform/chrome/cros_ec_chardev.c
index c9d80ad5b57e..f4aa70c8b6d4 100644
--- a/drivers/platform/chrome/cros_ec_chardev.c
+++ b/drivers/platform/chrome/cros_ec_chardev.c
@@ -22,6 +22,7 @@
#include <linux/platform_data/cros_ec_proto.h>
#include <linux/platform_device.h>
#include <linux/poll.h>
+#include <linux/ref_proxy.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/uaccess.h>
@@ -32,7 +33,7 @@
#define CROS_MAX_EVENT_LEN PAGE_SIZE
struct chardev_priv {
- struct cros_ec_device *ec_dev;
+ struct ref_proxy *ec_dev_proxy;
struct notifier_block notifier;
wait_queue_head_t wait_event;
unsigned long event_mask;
@@ -55,6 +56,7 @@ static int ec_get_version(struct chardev_priv *priv, char *str, int maxlen)
};
struct ec_response_get_version *resp;
struct cros_ec_command *msg;
+ struct cros_ec_device __rcu *ec_dev;
int ret;
msg = kzalloc(sizeof(*msg) + sizeof(*resp), GFP_KERNEL);
@@ -64,12 +66,19 @@ static int ec_get_version(struct chardev_priv *priv, char *str, int maxlen)
msg->command = EC_CMD_GET_VERSION + priv->cmd_offset;
msg->insize = sizeof(*resp);
- ret = cros_ec_cmd_xfer_status(priv->ec_dev, msg);
- if (ret < 0) {
- snprintf(str, maxlen,
- "Unknown EC version, returned error: %d\n",
- msg->result);
- goto exit;
+ REF_PROXY_GET(priv->ec_dev_proxy, ec_dev) {
+ if (!ec_dev) {
+ ret = -ENODEV;
+ goto exit;
+ }
+
+ ret = cros_ec_cmd_xfer_status(ec_dev, msg);
+ if (ret < 0) {
+ snprintf(str, maxlen,
+ "Unknown EC version, returned error: %d\n",
+ msg->result);
+ goto exit;
+ }
}
resp = (struct ec_response_get_version *)msg->data;
@@ -92,22 +101,30 @@ static int cros_ec_chardev_mkbp_event(struct notifier_block *nb,
{
struct chardev_priv *priv = container_of(nb, struct chardev_priv,
notifier);
- struct cros_ec_device *ec_dev = priv->ec_dev;
+ struct cros_ec_device __rcu *ec_dev;
struct ec_event *event;
- unsigned long event_bit = 1 << ec_dev->event_data.event_type;
- int total_size = sizeof(*event) + ec_dev->event_size;
+ unsigned long event_bit;
+ int total_size;
+
+ REF_PROXY_GET(priv->ec_dev_proxy, ec_dev) {
+ if (!ec_dev)
+ return NOTIFY_DONE;
- if (!(event_bit & priv->event_mask) ||
- (priv->event_len + total_size) > CROS_MAX_EVENT_LEN)
- return NOTIFY_DONE;
+ event_bit = 1 << ec_dev->event_data.event_type;
+ total_size = sizeof(*event) + ec_dev->event_size;
- event = kzalloc(total_size, GFP_KERNEL);
- if (!event)
- return NOTIFY_DONE;
+ if (!(event_bit & priv->event_mask) ||
+ (priv->event_len + total_size) > CROS_MAX_EVENT_LEN)
+ return NOTIFY_DONE;
- event->size = ec_dev->event_size;
- event->event_type = ec_dev->event_data.event_type;
- memcpy(event->data, &ec_dev->event_data.data, ec_dev->event_size);
+ event = kzalloc(total_size, GFP_KERNEL);
+ if (!event)
+ return NOTIFY_DONE;
+
+ event->size = ec_dev->event_size;
+ event->event_type = ec_dev->event_data.event_type;
+ memcpy(event->data, &ec_dev->event_data.data, ec_dev->event_size);
+ }
spin_lock(&priv->wait_event.lock);
list_add_tail(&event->node, &priv->events);
@@ -166,7 +183,12 @@ static int cros_ec_chardev_open(struct inode *inode, struct file *filp)
if (!priv)
return -ENOMEM;
- priv->ec_dev = ec_dev;
+ priv->ec_dev_proxy = ref_proxy_alloc(ec_dev->ref_proxy_provider);
+ if (!priv->ec_dev_proxy) {
+ ret = -ENOMEM;
+ goto err;
+ }
+
priv->cmd_offset = ec->cmd_offset;
filp->private_data = priv;
INIT_LIST_HEAD(&priv->events);
@@ -178,9 +200,14 @@ static int cros_ec_chardev_open(struct inode *inode, struct file *filp)
&priv->notifier);
if (ret) {
dev_err(ec_dev->dev, "failed to register event notifier\n");
- kfree(priv);
+ goto err;
}
+ return 0;
+err:
+ if (priv->ec_dev_proxy)
+ ref_proxy_free(priv->ec_dev_proxy);
+ kfree(priv);
return ret;
}
@@ -251,11 +278,16 @@ static ssize_t cros_ec_chardev_read(struct file *filp, char __user *buffer,
static int cros_ec_chardev_release(struct inode *inode, struct file *filp)
{
struct chardev_priv *priv = filp->private_data;
- struct cros_ec_device *ec_dev = priv->ec_dev;
+ struct cros_ec_device __rcu *ec_dev;
struct ec_event *event, *e;
- blocking_notifier_chain_unregister(&ec_dev->event_notifier,
- &priv->notifier);
+ REF_PROXY_GET(priv->ec_dev_proxy, ec_dev) {
+ if (ec_dev)
+ blocking_notifier_chain_unregister(
+ &ec_dev->event_notifier,
+ &priv->notifier);
+ }
+ ref_proxy_free(priv->ec_dev_proxy);
list_for_each_entry_safe(event, e, &priv->events, node) {
list_del(&event->node);
@@ -273,6 +305,7 @@ static long cros_ec_chardev_ioctl_xcmd(struct chardev_priv *priv, void __user *a
{
struct cros_ec_command *s_cmd;
struct cros_ec_command u_cmd;
+ struct cros_ec_device __rcu *ec_dev;
long ret;
if (copy_from_user(&u_cmd, arg, sizeof(u_cmd)))
@@ -299,10 +332,17 @@ static long cros_ec_chardev_ioctl_xcmd(struct chardev_priv *priv, void __user *a
}
s_cmd->command += priv->cmd_offset;
- ret = cros_ec_cmd_xfer(priv->ec_dev, s_cmd);
- /* Only copy data to userland if data was received. */
- if (ret < 0)
- goto exit;
+ REF_PROXY_GET(priv->ec_dev_proxy, ec_dev) {
+ if (!ec_dev) {
+ ret = -ENODEV;
+ goto exit;
+ }
+
+ ret = cros_ec_cmd_xfer(ec_dev, s_cmd);
+ /* Only copy data to userland if data was received. */
+ if (ret < 0)
+ goto exit;
+ }
if (copy_to_user(arg, s_cmd, sizeof(*s_cmd) + s_cmd->insize))
ret = -EFAULT;
@@ -313,24 +353,29 @@ static long cros_ec_chardev_ioctl_xcmd(struct chardev_priv *priv, void __user *a
static long cros_ec_chardev_ioctl_readmem(struct chardev_priv *priv, void __user *arg)
{
- struct cros_ec_device *ec_dev = priv->ec_dev;
+ struct cros_ec_device __rcu *ec_dev;
struct cros_ec_readmem s_mem = { };
long num;
- /* Not every platform supports direct reads */
- if (!ec_dev->cmd_readmem)
- return -ENOTTY;
+ REF_PROXY_GET(priv->ec_dev_proxy, ec_dev) {
+ if (!ec_dev)
+ return -ENODEV;
- if (copy_from_user(&s_mem, arg, sizeof(s_mem)))
- return -EFAULT;
+ /* Not every platform supports direct reads */
+ if (!ec_dev->cmd_readmem)
+ return -ENOTTY;
- if (s_mem.bytes > sizeof(s_mem.buffer))
- return -EINVAL;
+ if (copy_from_user(&s_mem, arg, sizeof(s_mem)))
+ return -EFAULT;
- num = ec_dev->cmd_readmem(ec_dev, s_mem.offset, s_mem.bytes,
- s_mem.buffer);
- if (num <= 0)
- return num;
+ if (s_mem.bytes > sizeof(s_mem.buffer))
+ return -EINVAL;
+
+ num = ec_dev->cmd_readmem(ec_dev, s_mem.offset, s_mem.bytes,
+ s_mem.buffer);
+ if (num <= 0)
+ return num;
+ }
if (copy_to_user((void __user *)arg, &s_mem, sizeof(s_mem)))
return -EFAULT;
--
2.51.0.rc1.163.g2494970778-googHi Tzung-Bi,
kernel test robot noticed the following build warnings:
[auto build test WARNING on chrome-platform/for-next]
[also build test WARNING on next-20250815]
[cannot apply to chrome-platform/for-firmware-next akpm-mm/mm-nonmm-unstable akpm-mm/mm-everything linus/master v6.17-rc1]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Tzung-Bi-Shih/lib-Add-ref_proxy-module/20250814-172126
base: https://git.kernel.org/pub/scm/linux/kernel/git/chrome-platform/linux.git for-next
patch link: https://lore.kernel.org/r/20250814091020.1302888-4-tzungbi%40kernel.org
patch subject: [PATCH 3/3] platform/chrome: cros_ec_chardev: Consume cros_ec_device via ref_proxy
config: i386-randconfig-061-20250815 (https://download.01.org/0day-ci/archive/20250816/202508161910.b7YHKLdh-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14+deb12u1) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250816/202508161910.b7YHKLdh-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202508161910.b7YHKLdh-lkp@intel.com/
sparse warnings: (new ones prefixed by >>)
>> drivers/platform/chrome/cros_ec_chardev.c:75:47: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected struct cros_ec_device *ec_dev @@ got struct cros_ec_device [noderef] __rcu *[assigned] ec_dev @@
drivers/platform/chrome/cros_ec_chardev.c:75:47: sparse: expected struct cros_ec_device *ec_dev
drivers/platform/chrome/cros_ec_chardev.c:75:47: sparse: got struct cros_ec_device [noderef] __rcu *[assigned] ec_dev
>> drivers/platform/chrome/cros_ec_chardev.c:126:17: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected void const * @@ got union ec_response_get_next_data_v3 [noderef] __rcu * @@
drivers/platform/chrome/cros_ec_chardev.c:126:17: sparse: expected void const *
drivers/platform/chrome/cros_ec_chardev.c:126:17: sparse: got union ec_response_get_next_data_v3 [noderef] __rcu *
>> drivers/platform/chrome/cros_ec_chardev.c:126:17: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected void const * @@ got union ec_response_get_next_data_v3 [noderef] __rcu * @@
drivers/platform/chrome/cros_ec_chardev.c:126:17: sparse: expected void const *
drivers/platform/chrome/cros_ec_chardev.c:126:17: sparse: got union ec_response_get_next_data_v3 [noderef] __rcu *
drivers/platform/chrome/cros_ec_chardev.c:126:17: sparse: sparse: incorrect type in argument 2 (different address spaces) @@ expected void const * @@ got union ec_response_get_next_data_v3 [noderef] __rcu * @@
drivers/platform/chrome/cros_ec_chardev.c:126:17: sparse: expected void const *
drivers/platform/chrome/cros_ec_chardev.c:126:17: sparse: got union ec_response_get_next_data_v3 [noderef] __rcu *
>> drivers/platform/chrome/cros_ec_chardev.c:287:42: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected struct blocking_notifier_head *nh @@ got struct blocking_notifier_head [noderef] __rcu * @@
drivers/platform/chrome/cros_ec_chardev.c:287:42: sparse: expected struct blocking_notifier_head *nh
drivers/platform/chrome/cros_ec_chardev.c:287:42: sparse: got struct blocking_notifier_head [noderef] __rcu *
drivers/platform/chrome/cros_ec_chardev.c:341:40: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected struct cros_ec_device *ec_dev @@ got struct cros_ec_device [noderef] __rcu *[assigned] ec_dev @@
drivers/platform/chrome/cros_ec_chardev.c:341:40: sparse: expected struct cros_ec_device *ec_dev
drivers/platform/chrome/cros_ec_chardev.c:341:40: sparse: got struct cros_ec_device [noderef] __rcu *[assigned] ec_dev
>> drivers/platform/chrome/cros_ec_chardev.c:374:43: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected struct cros_ec_device *ec @@ got struct cros_ec_device [noderef] __rcu *[assigned] ec_dev @@
drivers/platform/chrome/cros_ec_chardev.c:374:43: sparse: expected struct cros_ec_device *ec
drivers/platform/chrome/cros_ec_chardev.c:374:43: sparse: got struct cros_ec_device [noderef] __rcu *[assigned] ec_dev
>> drivers/platform/chrome/cros_ec_chardev.c:113:34: sparse: sparse: dereference of noderef expression
drivers/platform/chrome/cros_ec_chardev.c:114:47: sparse: sparse: dereference of noderef expression
drivers/platform/chrome/cros_ec_chardev.c:124:31: sparse: sparse: dereference of noderef expression
drivers/platform/chrome/cros_ec_chardev.c:125:37: sparse: sparse: dereference of noderef expression
drivers/platform/chrome/cros_ec_chardev.c:126:17: sparse: sparse: dereference of noderef expression
drivers/platform/chrome/cros_ec_chardev.c:365:22: sparse: sparse: dereference of noderef expression
drivers/platform/chrome/cros_ec_chardev.c:374:23: sparse: sparse: dereference of noderef expression
vim +75 drivers/platform/chrome/cros_ec_chardev.c
51
52 static int ec_get_version(struct chardev_priv *priv, char *str, int maxlen)
53 {
54 static const char * const current_image_name[] = {
55 "unknown", "read-only", "read-write", "invalid",
56 };
57 struct ec_response_get_version *resp;
58 struct cros_ec_command *msg;
59 struct cros_ec_device __rcu *ec_dev;
60 int ret;
61
62 msg = kzalloc(sizeof(*msg) + sizeof(*resp), GFP_KERNEL);
63 if (!msg)
64 return -ENOMEM;
65
66 msg->command = EC_CMD_GET_VERSION + priv->cmd_offset;
67 msg->insize = sizeof(*resp);
68
69 REF_PROXY_GET(priv->ec_dev_proxy, ec_dev) {
70 if (!ec_dev) {
71 ret = -ENODEV;
72 goto exit;
73 }
74
> 75 ret = cros_ec_cmd_xfer_status(ec_dev, msg);
76 if (ret < 0) {
77 snprintf(str, maxlen,
78 "Unknown EC version, returned error: %d\n",
79 msg->result);
80 goto exit;
81 }
82 }
83
84 resp = (struct ec_response_get_version *)msg->data;
85 if (resp->current_image >= ARRAY_SIZE(current_image_name))
86 resp->current_image = 3; /* invalid */
87
88 snprintf(str, maxlen, "%s\n%s\n%s\n%s\n", CROS_EC_DEV_VERSION,
89 resp->version_string_ro, resp->version_string_rw,
90 current_image_name[resp->current_image]);
91
92 ret = 0;
93 exit:
94 kfree(msg);
95 return ret;
96 }
97
98 static int cros_ec_chardev_mkbp_event(struct notifier_block *nb,
99 unsigned long queued_during_suspend,
100 void *_notify)
101 {
102 struct chardev_priv *priv = container_of(nb, struct chardev_priv,
103 notifier);
104 struct cros_ec_device __rcu *ec_dev;
105 struct ec_event *event;
106 unsigned long event_bit;
107 int total_size;
108
109 REF_PROXY_GET(priv->ec_dev_proxy, ec_dev) {
110 if (!ec_dev)
111 return NOTIFY_DONE;
112
> 113 event_bit = 1 << ec_dev->event_data.event_type;
114 total_size = sizeof(*event) + ec_dev->event_size;
115
116 if (!(event_bit & priv->event_mask) ||
117 (priv->event_len + total_size) > CROS_MAX_EVENT_LEN)
118 return NOTIFY_DONE;
119
120 event = kzalloc(total_size, GFP_KERNEL);
121 if (!event)
122 return NOTIFY_DONE;
123
124 event->size = ec_dev->event_size;
125 event->event_type = ec_dev->event_data.event_type;
> 126 memcpy(event->data, &ec_dev->event_data.data, ec_dev->event_size);
127 }
128
129 spin_lock(&priv->wait_event.lock);
130 list_add_tail(&event->node, &priv->events);
131 priv->event_len += total_size;
132 wake_up_locked(&priv->wait_event);
133 spin_unlock(&priv->wait_event.lock);
134
135 return NOTIFY_OK;
136 }
137
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Hi Tzung-Bi, kernel test robot noticed the following build errors: [auto build test ERROR on chrome-platform/for-next] [also build test ERROR on next-20250815] [cannot apply to chrome-platform/for-firmware-next akpm-mm/mm-nonmm-unstable akpm-mm/mm-everything linus/master v6.17-rc1] [If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in https://git-scm.com/docs/git-format-patch#_base_tree_information] url: https://github.com/intel-lab-lkp/linux/commits/Tzung-Bi-Shih/lib-Add-ref_proxy-module/20250814-172126 base: https://git.kernel.org/pub/scm/linux/kernel/git/chrome-platform/linux.git for-next patch link: https://lore.kernel.org/r/20250814091020.1302888-4-tzungbi%40kernel.org patch subject: [PATCH 3/3] platform/chrome: cros_ec_chardev: Consume cros_ec_device via ref_proxy config: hexagon-randconfig-r072-20250815 (https://download.01.org/0day-ci/archive/20250816/202508160456.eajfX7vH-lkp@intel.com/config) compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 93d24b6b7b148c47a2fa228a4ef31524fa1d9f3f) reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250816/202508160456.eajfX7vH-lkp@intel.com/reproduce) If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags | Reported-by: kernel test robot <lkp@intel.com> | Closes: https://lore.kernel.org/oe-kbuild-all/202508160456.eajfX7vH-lkp@intel.com/ All errors (new ones prefixed by >>, old ones prefixed by <<): >> ERROR: modpost: "ref_proxy_get" [drivers/platform/chrome/cros_ec_chardev.ko] undefined! >> ERROR: modpost: "ref_proxy_put" [drivers/platform/chrome/cros_ec_chardev.ko] undefined! >> ERROR: modpost: "ref_proxy_alloc" [drivers/platform/chrome/cros_ec_chardev.ko] undefined! >> ERROR: modpost: "ref_proxy_free" [drivers/platform/chrome/cros_ec_chardev.ko] undefined! -- 0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki
© 2016 - 2025 Red Hat, Inc.