[PATCH 4.19 81/81] perf/hw_breakpoint: Fix arch_hw_breakpoint use-before-initialization

[Greg Kroah-Hartman]

From: Mark-PK Tsai <mark-pk.tsai@xxxxxxxxxxxx>

commit 310aa0a25b338b3100c94880c9a69bec8ce8c3ae upstream.

If we disable the compiler's auto-initialization feature, if
-fplugin-arg-structleak_plugin-byref or -ftrivial-auto-var-init=pattern
are disabled, arch_hw_breakpoint may be used before initialization after:

  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 <mark-pk.tsai@xxxxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Alix Wu <alix.wu@xxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: YJ Chiang <yj.chiang@xxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20190906060115.9460-1-mark-pk.tsai@xxxxxxxxxxxx
[ Minor edits. ]
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Doug Anderson <dianders@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 kernel/events/hw_breakpoint.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -426,7 +426,7 @@ static int hw_breakpoint_parse(struct pe
 
 int register_perf_hw_breakpoint(struct perf_event *bp)
 {
-	struct arch_hw_breakpoint hw;
+	struct arch_hw_breakpoint hw = { };
 	int err;
 
 	err = reserve_bp_slot(bp);
@@ -474,7 +474,7 @@ 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 = { };
 	int err;
 
 	err = hw_breakpoint_parse(bp, attr, &hw);