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Compiling with USE_HIDAPI (hid_hidapi.c) generate a race condition when unlocking multiple devices #995
Description
What version of libfido2 are you using?
1.16.0 / main
What operating system are you running?
Linux (openSUSE)
What application are you using in conjunction with libfido2?
systemd (v261.2)
How does the problem manifest itself?
When multiple devices needs to be unlocked and USE_HIDAPI is used as a compilation option, we have this error:
Failed to open FIDO2 device /dev/hidraw2: FIDO_ERR_RX
Token returned error during pre-flight: Input/output error
Is the problem reproducible?
Yes, for a direct reproducer see: systemd/systemd#35671
What are the steps that lead to the problem?
Seem that the problem is related to using hid_hidapi.c, that does not use flock in contrast as hid_linux.c.
Activity
dacav commentedon Oct 6, 2026
@aplanas
I could reproduce the problem. The fix you suggest seems to do the job: #1001
I need to test it further, and make sure it is portable.
dacav commentedon Oct 12, 2026
@aplanas
I checked some portability.
I don't have time to look into more, for the moment. But would the current changes in #1001 work for your case?
It seems to have fixed the problem at my side.