Fix potential memory leak in vinput #279
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In the export_store function, the error handling paths followed a successful vinput_alloc_vdevice call are missing a corresponding input_free_device call. Since vinput_alloc_vdevice internally calls input_allocate_device, and input_register_device has not been called yet, input_free_device should be used to properly free the allocated input_device struct in this scenario[1]. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/input/input.c#n2094
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Can you make use of eBPF to locate memory errors? |
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I never used eBPF before, I'll try it at night. |
kmemleak is really powerful, and you should try it. |
Great!
Update: I misunderstood how to use kmodleak. It only takes the module name as the tracing target and doesn't actively load or unload modules. |
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Here's the outputs from kmodleak. (original code) (patched code) |
linD026
requested changes
Oct 26, 2024
| @@ -283,10 +283,12 @@ static ssize_t export_store(struct class *class, struct class_attribute *attr, | |||
| return len; | |||
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| fail_register_vinput: | |||
| input_free_device(vinput->input); | |||
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If we call input_allocate_device in vinput_alloc_vdevice , why do we handle it manually instead of putting input_free_device in the corresponding release function?
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I believe input_free_device should be decoupled from the release function vinput_destroy_vdevice. In both unexport_store and vinput_unregister, the vinput_unregister_vdevice function is called before device_unregister, with each invoking input_unregister_device followed by vinput_destroy_vdevice. Embedding input_free_device within vinput_destroy_vdevice could contradict the documented comments in the source code [1].
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/input/input.c#n2386
linD026
approved these changes
Oct 26, 2024
We can even automate the use of kmodleak, enforcing the checks for all loadable Linux modules in CI pipeline. |
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In the export_store function, the error handling paths followed a successful vinput_alloc_vdevice call are missing a corresponding input_free_device call. Since vinput_alloc_vdevice internally calls input_allocate_device, and input_register_device has not been called yet, input_free_device should be used to properly free the allocated input_device struct in this scenario[1].
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/input/input.c#n2094