diff options
| author | Will Deacon <willdeacon@google.com> | 2020-12-15 16:24:55 +0000 |
|---|---|---|
| committer | Giuliano Procida <gprocida@google.com> | 2021-01-05 15:58:52 +0000 |
| commit | b5b38b010efc2330816691b98bb6cb9ec7e80d68 (patch) | |
| tree | ef0babd693af520bc93eec2155b9947bf026d520 | |
| parent | 65ab8d94757f5e5198da6584c7f94509128e333e (diff) | |
ANDROID: usb: f_accessory: Don't corrupt global state on double registration
If acc_setup() is called when there is already an allocated instance,
misc_register() will fail but the error path leaves a dangling pointer
to freed memory in the global 'acc_dev' state.
Fix this by ensuring that the refcount is zero before we start, and then
using a cmpxchg() from NULL to serialise any concurrent initialisers.
Bug: 173789633
Signed-off-by: Will Deacon <willdeacon@google.com>
Change-Id: I2c26289dcce7dbc493964516c49b05d04aaa6839
Signed-off-by: Giuliano Procida <gprocida@google.com>
| -rw-r--r-- | drivers/usb/gadget/function/f_accessory.c | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/drivers/usb/gadget/function/f_accessory.c b/drivers/usb/gadget/function/f_accessory.c index 4aa4a57d0fc5..b48d75657012 100644 --- a/drivers/usb/gadget/function/f_accessory.c +++ b/drivers/usb/gadget/function/f_accessory.c @@ -1259,6 +1259,9 @@ static int acc_setup(void) struct acc_dev *dev; int ret; + if (kref_read(&ref->kref)) + return -EBUSY; + dev = kzalloc(sizeof(*dev), GFP_KERNEL); if (!dev) return -ENOMEM; @@ -1275,16 +1278,21 @@ static int acc_setup(void) INIT_WORK(&dev->hid_work, acc_hid_work); dev->ref = ref; - kref_init(&ref->kref); - ref->acc_dev = dev; + if (cmpxchg_relaxed(&ref->acc_dev, NULL, dev)) { + ret = -EBUSY; + goto err_free_dev; + } ret = misc_register(&acc_device); if (ret) - goto err; + goto err_zap_ptr; + kref_init(&ref->kref); return 0; -err: +err_zap_ptr: + ref->acc_dev = NULL; +err_free_dev: kfree(dev); pr_err("USB accessory gadget driver failed to initialize\n"); return ret; |