Re: [PATCH] selftests/tty: tiocsti: expect the privileged parent to succeed

[sashiko-bot@kernel.org]

> The FD passing tests open a pty in a child process, which may drop its
> privileges first, and pass the FD to the parent, which always has
> CAP_SYS_ADMIN. The child's own TIOCSTI is checked against
> .expected_success, and so is the parent's TIOCSTI on the passed FD.
> 
> TIOCSTI checks the capabilities of the caller, not those of the process
> that opened the tty, so the parent always succeeds. Where the child has
> dropped its privileges and is expected to fail, the parent's check fails
> instead:
> 
>   # tty_tiocsti_test.c:620:test:Expected result (0) == variant->expected_success (-5)
>   # tty_tiocsti_test.c:622:test:FD passing: expected error -5, got 0
>   ...
>   # FAILED: 13 / 16 tests passed.
> 
> [ ... ]
> 
> Fixes: 7553f5173ec3 ("selftests/tty: add TIOCSTI test suite")
> Link: https://lore.kernel.org/all/2025062327-shady-broadcast-237d@gregkh/
> Link: https://lore.kernel.org/all/20250624.3bb75890f0b0@gnoack.org/
> Signed-off-by: Danish Khateeb <danishkhateeb03@gmail.com>

Sashiko has reviewed this patch and found no issues.

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