This is a note to let you know that I've just added the patch titled
mm/damon/core: make damon_start() waits until kdamond_fn() starts
to the 6.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-damon-core-make-damon_start-waits-until-kdamond_fn-starts.patch
and it can be found in the queue-6.1 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6376a824595607e99d032a39ba3394988b4fce96 Mon Sep 17 00:00:00 2001
From: SeongJae Park <sj@xxxxxxxxxx>
Date: Fri, 8 Dec 2023 17:50:18 +0000
Subject: mm/damon/core: make damon_start() waits until kdamond_fn() starts
From: SeongJae Park <sj@xxxxxxxxxx>
commit 6376a824595607e99d032a39ba3394988b4fce96 upstream.
The cleanup tasks of kdamond threads including reset of corresponding
DAMON context's ->kdamond field and decrease of global nr_running_ctxs
counter is supposed to be executed by kdamond_fn(). However, commit
0f91d13366a4 ("mm/damon: simplify stop mechanism") made neither
damon_start() nor damon_stop() ensure the corresponding kdamond has
started the execution of kdamond_fn().
As a result, the cleanup can be skipped if damon_stop() is called fast
enough after the previous damon_start(). Especially the skipped reset
of ->kdamond could cause a use-after-free.
Fix it by waiting for start of kdamond_fn() execution from
damon_start().
Link: https://lkml.kernel.org/r/20231208175018.63880-1-sj@xxxxxxxxxx
Fixes: 0f91d13366a4 ("mm/damon: simplify stop mechanism")
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
Reported-by: Jakub Acs <acsjakub@xxxxxxxxx>
Cc: Changbin Du <changbin.du@xxxxxxxxx>
Cc: Jakub Acs <acsjakub@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 5.15.x
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
include/linux/damon.h | 3 +++
mm/damon/core.c | 7 +++++++
2 files changed, 10 insertions(+)
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -8,6 +8,7 @@
#ifndef _DAMON_H_
#define _DAMON_H_
+#include <linux/completion.h>
#include <linux/mutex.h>
#include <linux/time64.h>
#include <linux/types.h>
@@ -452,6 +453,8 @@ struct damon_ctx {
/* private: internal use only */
struct timespec64 last_aggregation;
struct timespec64 last_ops_update;
+ /* for waiting until the execution of the kdamond_fn is started */
+ struct completion kdamond_started;
/* public: */
struct task_struct *kdamond;
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -383,6 +383,8 @@ struct damon_ctx *damon_new_ctx(void)
if (!ctx)
return NULL;
+ init_completion(&ctx->kdamond_started);
+
ctx->attrs.sample_interval = 5 * 1000;
ctx->attrs.aggr_interval = 100 * 1000;
ctx->attrs.ops_update_interval = 60 * 1000 * 1000;
@@ -519,11 +521,14 @@ static int __damon_start(struct damon_ct
mutex_lock(&ctx->kdamond_lock);
if (!ctx->kdamond) {
err = 0;
+ reinit_completion(&ctx->kdamond_started);
ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond.%d",
nr_running_ctxs);
if (IS_ERR(ctx->kdamond)) {
err = PTR_ERR(ctx->kdamond);
ctx->kdamond = NULL;
+ } else {
+ wait_for_completion(&ctx->kdamond_started);
}
}
mutex_unlock(&ctx->kdamond_lock);
@@ -1147,6 +1152,8 @@ static int kdamond_fn(void *data)
pr_debug("kdamond (%d) starts\n", current->pid);
+ complete(&ctx->kdamond_started);
+
if (ctx->ops.init)
ctx->ops.init(ctx);
if (ctx->callback.before_start && ctx->callback.before_start(ctx))
Patches currently in stable-queue which might be from sj@xxxxxxxxxx are
queue-6.1/mm-damon-core-make-damon_start-waits-until-kdamond_fn-starts.patch
