ARM: 9064/1: hw_breakpoint: Do not directly check the event's overflow_handler hook

stable inclusion
from stable-v4.19.191
commit a9938d6d78a238d6ab8de57a4d3dcf77adceb9bb
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I94K5W
CVE: CVE-2021-47006

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a9938d6d78a238d6ab8de57a4d3dcf77adceb9bb

--------------------------------

The commit 1879445d ("perf/core: Set event's default
::overflow_handler()") set a default event->overflow_handler in
perf_event_alloc(), and replace the check event->overflow_handler with
is_default_overflow_handler(), but one is missing.

Currently, the bp->overflow_handler can not be NULL. As a result,
enable_single_step() is always not invoked.

Comments from Zhen Lei:

 https://patchwork.kernel.org/project/linux-arm-kernel/patch/20210207105934.2001-1-thunder.leizhen@huawei.com/



Fixes: 1879445d ("perf/core: Set event's default ::overflow_handler()")
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Cc: Wang Nan <wangnan0@huawei.com>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yuntao Liu <liuyuntao12@huawei.com>