* + mm-damon-core-remove-call_control-in-inactive-contexts.patch added to mm-hotfixes-unstable branch
@ 2025-12-27 15:42 Andrew Morton
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2025-12-27 15:42 UTC (permalink / raw)
To: mm-commits, stable, rgbi3307, sj, akpm
The patch titled
Subject: mm/damon/core: remove call_control in inactive contexts
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-damon-core-remove-call_control-in-inactive-contexts.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-remove-call_control-in-inactive-contexts.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days
------------------------------------------------------
From: SeongJae Park <sj@kernel.org>
Subject: mm/damon/core: remove call_control in inactive contexts
Date: Tue, 30 Dec 2025 17:23:13 -0800
If damon_call() is executed against a DAMON context that is not running,
the function returns error while keeping the damon_call_control object
linked to the context's call_controls list. Let's suppose the object is
deallocated after the damon_call(), and yet another damon_call() is
executed against the same context. The function tries to add the new
damon_call_control object to the call_controls list, which still has the
pointer to the previous damon_call_control object, which is deallocated.
As a result, use-after-free happens.
This can actually be triggered using the DAMON sysfs interface. It is not
easily exploitable since it requires the sysfs write permission and making
a definitely weird file writes, though. Please refer to the report for
more details about the issue reproduction steps.
Fix the issue by making two changes. Firstly, move the final
kdamond_call() for cancelling all existing damon_call() requests from
terminating DAMON context to be done before the ctx->kdamond reset. This
makes any code that sees NULL ctx->kdamond can safely assume the context
may not access damon_call() requests anymore. Secondly, let damon_call()
to cleanup the damon_call_control objects that were added to the
already-terminated DAMON context, before returning the error.
Link: https://lkml.kernel.org/r/20251231012315.75835-1-sj@kernel.org
Fixes: 004ded6bee11 ("mm/damon: accept parallel damon_call() requests")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: JaeJoon Jung <rgbi3307@gmail.com>
Closes: https://lore.kernel.org/20251224094401.20384-1-rgbi3307@gmail.com
Cc: <stable@vger.kernel.org> # 6.17.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/damon/core.c | 33 +++++++++++++++++++++++++++++++--
1 file changed, 31 insertions(+), 2 deletions(-)
--- a/mm/damon/core.c~mm-damon-core-remove-call_control-in-inactive-contexts
+++ a/mm/damon/core.c
@@ -1431,6 +1431,35 @@ bool damon_is_running(struct damon_ctx *
return running;
}
+/*
+ * damon_call_handle_inactive_ctx() - handle DAMON call request that added to
+ * an inactive context.
+ * @ctx: The inactive DAMON context.
+ * @control: Control variable of the call request.
+ *
+ * This function is called in a case that @control is added to @ctx but @ctx is
+ * not running (inactive). See if @ctx handled @control or not, and cleanup
+ * @control if it was not handled.
+ *
+ * Returns 0 if @control was handled by @ctx, negative error code otherwise.
+ */
+static int damon_call_handle_inactive_ctx(
+ struct damon_ctx *ctx, struct damon_call_control *control)
+{
+ struct damon_call_control *c;
+
+ mutex_lock(&ctx->call_controls_lock);
+ list_for_each_entry(c, &ctx->call_controls, list) {
+ if (c == control) {
+ list_del(&control->list);
+ mutex_unlock(&ctx->call_controls_lock);
+ return -EINVAL;
+ }
+ }
+ mutex_unlock(&ctx->call_controls_lock);
+ return 0;
+}
+
/**
* damon_call() - Invoke a given function on DAMON worker thread (kdamond).
* @ctx: DAMON context to call the function for.
@@ -1461,7 +1490,7 @@ int damon_call(struct damon_ctx *ctx, st
list_add_tail(&control->list, &ctx->call_controls);
mutex_unlock(&ctx->call_controls_lock);
if (!damon_is_running(ctx))
- return -EINVAL;
+ return damon_call_handle_inactive_ctx(ctx, control);
if (control->repeat)
return 0;
wait_for_completion(&control->completion);
@@ -2755,13 +2784,13 @@ done:
if (ctx->ops.cleanup)
ctx->ops.cleanup(ctx);
kfree(ctx->regions_score_histogram);
+ kdamond_call(ctx, true);
pr_debug("kdamond (%d) finishes\n", current->pid);
mutex_lock(&ctx->kdamond_lock);
ctx->kdamond = NULL;
mutex_unlock(&ctx->kdamond_lock);
- kdamond_call(ctx, true);
damos_walk_cancel(ctx);
mutex_lock(&damon_lock);
_
Patches currently in -mm which might be from sj@kernel.org are
mm-damon-core-remove-call_control-in-inactive-contexts.patch
mm-damon-core-introduce-nr_snapshots-damos-stat.patch
mm-damon-sysfs-schemes-introduce-nr_snapshots-damos-stat-file.patch
docs-mm-damon-design-update-for-nr_snapshots-damos-stat.patch
docs-admin-guide-mm-damon-usage-update-for-nr_snapshots-damos-stat.patch
docs-abi-damon-update-for-nr_snapshots-damos-stat.patch
mm-damon-update-damos-kerneldoc-for-stat-field.patch
mm-damon-core-implement-max_nr_snapshots.patch
mm-damon-sysfs-schemes-implement-max_nr_snapshots-file.patch
docs-mm-damon-design-update-for-max_nr_snapshots.patch
docs-admin-guide-mm-damon-usage-update-for-max_nr_snapshots.patch
docs-abi-damon-update-for-max_nr_snapshots.patch
mm-damon-core-add-trace-point-for-damos-stat-per-apply-interval.patch
mm-damon-sysfs-cleanup-intervals-subdirs-on-attrs-dir-setup-failure.patch
mm-damon-sysfs-cleanup-attrs-subdirs-on-context-dir-setup-failure.patch
mm-damon-sysfs-scheme-cleanup-quotas-subdirs-on-scheme-dir-setup-failure.patch
mm-damon-sysfs-scheme-cleanup-access_pattern-subdirs-on-scheme-dir-setup-failure.patch
mm-damon-tests-core-kunit-add-test-cases-for-multiple-regions-in-damon_test_split_regions_of-fix.patch
^ permalink raw reply [flat|nested] 2+ messages in thread
* + mm-damon-core-remove-call_control-in-inactive-contexts.patch added to mm-hotfixes-unstable branch
@ 2025-12-28 19:12 Andrew Morton
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2025-12-28 19:12 UTC (permalink / raw)
To: mm-commits, stable, rgbi3307, sj, akpm
The patch titled
Subject: mm/damon/core: remove call_control in inactive contexts
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-damon-core-remove-call_control-in-inactive-contexts.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-remove-call_control-in-inactive-contexts.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via various
branches at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there most days
------------------------------------------------------
From: SeongJae Park <sj@kernel.org>
Subject: mm/damon/core: remove call_control in inactive contexts
Date: Sun, 28 Dec 2025 10:31:01 -0800
If damon_call() is executed against a DAMON context that is not running,
the function returns error while keeping the damon_call_control object
linked to the context's call_controls list. Let's suppose the object is
deallocated after the damon_call(), and yet another damon_call() is
executed against the same context. The function tries to add the new
damon_call_control object to the call_controls list, which still has the
pointer to the previous damon_call_control object, which is deallocated.
As a result, use-after-free happens.
This can actually be triggered using the DAMON sysfs interface. It is not
easily exploitable since it requires the sysfs write permission and making
a definitely weird file writes, though. Please refer to the report for
more details about the issue reproduction steps.
Fix the issue by making damon_call() to cleanup the damon_call_control
object before returning the error.
Link: https://lkml.kernel.org/r/20251228183105.289441-1-sj@kernel.org
Fixes: 42b7491af14c ("mm/damon/core: introduce damon_call()")
Signed-off-by: SeongJae Park <sj@kernel.org>
Reported-by: JaeJoon Jung <rgbi3307@gmail.com>
Closes: https://lore.kernel.org/20251224094401.20384-1-rgbi3307@gmail.com
Cc: <stable@vger.kernel.org> [6.14+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
mm/damon/core.c | 31 ++++++++++++++++++++++++++++++-
1 file changed, 30 insertions(+), 1 deletion(-)
--- a/mm/damon/core.c~mm-damon-core-remove-call_control-in-inactive-contexts
+++ a/mm/damon/core.c
@@ -1431,6 +1431,35 @@ bool damon_is_running(struct damon_ctx *
return running;
}
+/*
+ * damon_call_handle_inactive_ctx() - handle DAMON call request that added to
+ * an inactive context.
+ * @ctx: The inactive DAMON context.
+ * @control: Control variable of the call request.
+ *
+ * This function is called in a case that @control is added to @ctx but @ctx is
+ * not running (inactive). See if @ctx handled @control or not, and cleanup
+ * @control if it was not handled.
+ *
+ * Returns 0 if @control was handled by @ctx, negative error code otherwise.
+ */
+static int damon_call_handle_inactive_ctx(
+ struct damon_ctx *ctx, struct damon_call_control *control)
+{
+ struct damon_call_control *c;
+
+ mutex_lock(&ctx->call_controls_lock);
+ list_for_each_entry(c, &ctx->call_controls, list) {
+ if (c == control) {
+ list_del(&control->list);
+ mutex_unlock(&ctx->call_controls_lock);
+ return -EINVAL;
+ }
+ }
+ mutex_unlock(&ctx->call_controls_lock);
+ return 0;
+}
+
/**
* damon_call() - Invoke a given function on DAMON worker thread (kdamond).
* @ctx: DAMON context to call the function for.
@@ -1461,7 +1490,7 @@ int damon_call(struct damon_ctx *ctx, st
list_add_tail(&control->list, &ctx->call_controls);
mutex_unlock(&ctx->call_controls_lock);
if (!damon_is_running(ctx))
- return -EINVAL;
+ return damon_call_handle_inactive_ctx(ctx, control);
if (control->repeat)
return 0;
wait_for_completion(&control->completion);
_
Patches currently in -mm which might be from sj@kernel.org are
mm-damon-core-remove-call_control-in-inactive-contexts.patch
mm-damon-core-introduce-nr_snapshots-damos-stat.patch
mm-damon-sysfs-schemes-introduce-nr_snapshots-damos-stat-file.patch
docs-mm-damon-design-update-for-nr_snapshots-damos-stat.patch
docs-admin-guide-mm-damon-usage-update-for-nr_snapshots-damos-stat.patch
docs-abi-damon-update-for-nr_snapshots-damos-stat.patch
mm-damon-update-damos-kerneldoc-for-stat-field.patch
mm-damon-core-implement-max_nr_snapshots.patch
mm-damon-sysfs-schemes-implement-max_nr_snapshots-file.patch
docs-mm-damon-design-update-for-max_nr_snapshots.patch
docs-admin-guide-mm-damon-usage-update-for-max_nr_snapshots.patch
docs-abi-damon-update-for-max_nr_snapshots.patch
mm-damon-core-add-trace-point-for-damos-stat-per-apply-interval.patch
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