Subject: [PATCH] perf/hw_breakpoint: Fix arch_hw_breakpoint use-before-initialization

From: Mark-PK Tsai <[email-masked]>
Date: Fri, 6 Sep 2019 14:01:16 +0800

If we disable the compiler's auto-initialization feature
(-fplugin-arg-structleak_plugin-byref or -ftrivial-auto-var-init=pattern)
is disabled, arch_hw_breakpoint may be used before initialization after
the change 9a4903dde2c86.
(perf/hw_breakpoint: Split attribute parse and commit)

On our arm platform, the struct step_ctrl in arch_hw_breakpoint, which
used to be zero-initialized by kzalloc, may be used in
arch_install_hw_breakpoint without initialization.

Signed-off-by: Mark-PK Tsai <[email-masked]>
Cc: YJ Chiang <[email-masked]>
Cc: Alix Wu <[email-masked]>
---
 kernel/events/hw_breakpoint.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index c5cd852fe86b..8fb842394924 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -413,7 +413,7 @@ static int hw_breakpoint_parse(struct perf_event *bp,

 int register_perf_hw_breakpoint(struct perf_event *bp)
 {
-	struct arch_hw_breakpoint hw;
+	struct arch_hw_breakpoint hw = {0};
 	int err;

 	err = reserve_bp_slot(bp);
@@ -461,7 +461,7 @@ int
 modify_user_hw_breakpoint_check(struct perf_event *bp, struct perf_event_attr *attr,
 			        bool check)
 {
-	struct arch_hw_breakpoint hw;
+	struct arch_hw_breakpoint hw = {0};
 	int err;

 	err = hw_breakpoint_parse(bp, attr, &hw);
--
2.18.0

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