selftests/timers: clocksource-switch: Fix unchecked open()/read()

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@kylinos.cn>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Acked-by: John Stultz <jstultz@google.com>
Link: https://patch.msgid.link/20260825064605.472889-1-fffsqian@163.com

0 files changed, 0 insertions, 0 deletions