The patch titled
Subject: mm/damon/core: make damon_start() waits until kdamond_fn() starts
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-damon-core-make-damon_start-waits-until-kdamond_fn-starts.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-core-make-damon_start-waits-until-kdamond_fn-starts.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: SeongJae Park <sj@xxxxxxxxxx>
Subject: mm/damon/core: make damon_start() waits until kdamond_fn() starts
Date: Fri, 8 Dec 2023 17:50:18 +0000
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>
---
include/linux/damon.h | 2 ++
mm/damon/core.c | 6 ++++++
2 files changed, 8 insertions(+)
--- a/include/linux/damon.h~mm-damon-core-make-damon_start-waits-until-kdamond_fn-starts
+++ a/include/linux/damon.h
@@ -559,6 +559,8 @@ struct damon_ctx {
* update
*/
unsigned long next_ops_update_sis;
+ /* 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~mm-damon-core-make-damon_start-waits-until-kdamond_fn-starts
+++ a/mm/damon/core.c
@@ -445,6 +445,8 @@ 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;
@@ -668,11 +670,14 @@ 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);
@@ -1433,6 +1438,7 @@ static int kdamond_fn(void *data)
pr_debug("kdamond (%d) starts\n", current->pid);
+ complete(&ctx->kdamond_started);
kdamond_init_intervals_sis(ctx);
if (ctx->ops.init)
_
Patches currently in -mm which might be from sj@xxxxxxxxxx are
mm-damon-core-make-damon_start-waits-until-kdamond_fn-starts.patch
mm-damon-core-test-test-damon_split_region_ats-access-rate-copying.patch
mm-damon-core-implement-goal-oriented-feedback-driven-quota-auto-tuning.patch
mm-damon-core-implement-goal-oriented-feedback-driven-quota-auto-tuning-fix.patch
mm-damon-sysfs-schemes-implement-files-for-scheme-quota-goals-setup.patch
mm-damon-sysfs-schemes-commit-damos-quota-goals-user-input-to-damos.patch
mm-damon-sysfs-schemes-implement-a-command-for-scheme-quota-goals-only-commit.patch
mm-damon-core-test-add-a-unit-test-for-the-feedback-loop-algorithm.patch
selftests-damon-test-quota-goals-directory.patch
docs-mm-damon-design-document-damos-quota-auto-tuning.patch
docs-abi-damon-document-damos-quota-goals.patch
docs-admin-guide-mm-damon-usage-document-for-quota-goals.patch
