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SubjectRe: [PATCH] hid: hid-core: Fix a sleep-in-atomic-context bug in __hid_request()
On Sat, 1 Sep 2018, Jia-Ju Bai wrote:

> The driver may sleep with holding a spinlock.
>
> The function call paths (from bottom to top) in Linux-4.16 are:
>
> [FUNC] hid_alloc_report_buf(GFP_KERNEL)
> drivers/hid/hid-core.c, 1435:
> hid_alloc_report_buf in __hid_request
> ./include/linux/hid.h, 1023:
> __hid_request in hid_hw_request
> drivers/hid/hid-picolcd_core.c, 111:
> hid_hw_request in picolcd_send_and_wait
> drivers/hid/hid-picolcd_core.c, 100:
> _raw_spin_lock_irqsave in picolcd_send_and_wait
>
> [FUNC] hid_alloc_report_buf(GFP_KERNEL)
> drivers/hid/hid-core.c, 1435:
> hid_alloc_report_buf in __hid_request
> ./include/linux/hid.h, 1023:
> __hid_request in hid_hw_request
> drivers/hid/hid-picolcd_core.c, 245:
> hid_hw_request in picolcd_reset
> drivers/hid/hid-picolcd_core.c, 235:
> _raw_spin_lock_irqsave in picolcd_reset
>
> [FUNC] hid_alloc_report_buf(GFP_KERNEL)
> drivers/hid/hid-core.c, 1435:
> hid_alloc_report_buf in __hid_request
> ./include/linux/hid.h, 1023:
> __hid_request in hid_hw_request
> drivers/hid/hid-picolcd_fb.c, 215:
> hid_hw_request in picolcd_fb_reset
> drivers/hid/hid-picolcd_fb.c, 206:
> _raw_spin_lock_irqsave in picolcd_fb_reset
>
> [FUNC] hid_alloc_report_buf(GFP_KERNEL)
> drivers/hid/hid-core.c, 1435:
> hid_alloc_report_buf in __hid_request
> ./include/linux/hid.h, 1023:
> __hid_request in hid_hw_request
> drivers/hid/hid-lg4ff.c, 465:
> hid_hw_request in lg4ff_play
> drivers/hid/hid-lg4ff.c, 441:
> _raw_spin_lock_irqsave in lg4ff_play
>
> To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.
>
> This bug is found by my static analysis tool DSAC.

Could you please rewrite the changelog so that it's human readable? The
above is a bit hard to understand, I think something along the lines of
"__hid_request() has to be allocating with GFP_ATOMIC because there are
the following callchains leading to __hid_request() being an atomic
context: ... a->b->c.._hid_request()" etc.

Thanks,

--
Jiri Kosina
SUSE Labs

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