linux-kernel - [PATCH] uprobes: use READ_ONCE() to read mm->uprobes_state.xol

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Message-ID: <tencent_088804E150842691191FD0021AEE8649EB0A@qq.com>
Date: Sat, 24 Feb 2024 18:25:19 +0800
From: linke li <lilinke99@...com>
To: 
Cc: lilinke99@...com,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] uprobes: use READ_ONCE() to read mm->uprobes_state.xol_area in concurrent environment

In function get_xol_area(), mm->uprobes_state.xol_area is read using 
READ_ONCE() in line 1534

1534   area = READ_ONCE(mm->uprobes_state.xol_area); /* ^^^ */

while read directly in line 1530

1530   	if (!mm->uprobes_state.xol_area)
1531	    __create_xol_area(0);

In the same environment, reads in two places should have the same
protection.

Signed-off-by: linke li <lilinke99@...com>
---
 kernel/events/uprobes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 929e98c62965..e110941fbc6b 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1527,7 +1527,7 @@ static struct xol_area *get_xol_area(void)
 	struct mm_struct *mm = current->mm;
 	struct xol_area *area;
 
-	if (!mm->uprobes_state.xol_area)
+	if (!READ_ONCE(mm->uprobes_state.xol_area))
 		__create_xol_area(0);
 
 	/* Pairs with xol_add_vma() smp_store_release() */
-- 
2.39.3 (Apple Git-145)