Got the following oops just before reboot:
Unable to handle kernel NULL pointer dereference at virtual address 00000000
[<8028d300>] (__list_del_entry+0x44/0xac)
[<802e3320>] (__fw_load_abort.part.13+0x1c/0x50)
[<802e337c>] (fw_shutdown_notify+0x28/0x50)
[<80034f80>] (notifier_call_chain.isra.1+0x5c/0x9c)
[<800350ec>] (__blocking_notifier_call_chain+0x44/0x58)
[<80035114>] (blocking_notifier_call_chain+0x14/0x18)
[<80035d64>] (kernel_restart_prepare+0x14/0x38)
[<80035d94>] (kernel_restart+0xc/0x50)
The following race condition triggers here:
_request_firmware_load()
device_create_file(...)
kobject_uevent(...)
(schedule)
(resume)
firmware_loading_store(1)
firmware_loading_store(0)
list_del_init(&buf->pending_list)
(schedule)
(resume)
list_add(&buf->pending_list, &pending_fw_head);
wait_for_completion(&buf->completion);
causing an oops later when walking pending_list after the firmware has
been released.
The proposed fix is to move the list_add() before sysfs attribute
creation.
Signed-off-by: Maxime Bizon <mbi...@freebox.fr>
---
drivers/base/firmware_class.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index a439602..c8dac74 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -868,8 +868,15 @@ static int _request_firmware_load(struct firmware_priv
*fw_priv, bool uevent,
goto err_del_dev;
}
+ mutex_lock(&fw_lock);
+ list_add(&buf->pending_list, &pending_fw_head);
+ mutex_unlock(&fw_lock);
+
retval = device_create_file(f_dev, &dev_attr_loading);
if (retval) {
+ mutex_lock(&fw_lock);
+ list_del_init(&buf->pending_list);
+ mutex_unlock(&fw_lock);
dev_err(f_dev, "%s: device_create_file failed\n", __func__);
goto err_del_bin_attr;
}
@@ -884,10 +891,6 @@ static int _request_firmware_load(struct firmware_priv
*fw_priv, bool uevent,
kobject_uevent(&fw_priv->dev.kobj, KOBJ_ADD);
}
- mutex_lock(&fw_lock);
- list_add(&buf->pending_list, &pending_fw_head);
- mutex_unlock(&fw_lock);
-
wait_for_completion(&buf->completion);
cancel_delayed_work_sync(&fw_priv->timeout_work);
--
1.7.9.5
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