Re: [PATCH selftests/timers] selftests/timers: clocksource-switch: fix unchecked open()/read()

[John Stultz]

On Mon, Aug 24, 2026 at 11:46 PM Qingshuang Fu <fffsqian@xxxxxxx> wrote:
>
> From: Qingshuang Fu <fuqingshuang@xxxxxxxxxx>
>
> get_clocksources() and get_cur_clocksource() open and read the
> clocksource sysfs files without checking the return values and without
> NUL-terminating the buffer.
>
> If open() fails, read() is called on fd -1 and returns -1, which is
> stored in a size_t as SIZE_MAX.  The token-scanning loop in
> get_clocksources() then walks past the uninitialized stack buffer,
> reading and writing out of bounds.  Even on success the buffer is not
> NUL-terminated, so a fully read buffer makes the inner scan run past the
> data, and get_cur_clocksource() lets change_clocksource() call strlen()
> on a non-terminated buffer.
>
> Check the open()/read() results, use ssize_t for the read length,
> NUL-terminate the buffer, and close the fd in get_cur_clocksource().
>
> Fixes: 7290ce1423c3 ("selftests/timers: Add clocksource-switch test from timetest suite")
> Signed-off-by: Qingshuang Fu <fuqingshuang@xxxxxxxxxx>

Acked-by: John Stultz <jstultz@xxxxxxxxxx>