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mm/damon/lru_sort: skip damon_call() if ctx has not started

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DAMON_LRU_SORT calls damon_call() for commit_inputs parameter user input
if the DAMON context is initialized.  The context could be initialized,
but not yet successfully started.  In the case, damon_call() could
indefinitely hang.  Read the comment on damon_call() for more detail.  Fix
the problem by memorizing if the DAMON context has ever successfully
started, and skip damon_call() if it has not.

This issue can easily be reproduced by writing Y to the commit_inputs
parameter file on a system that DAMON_LRU_SORT has not turned on before.

Link: https://lore.kernel.org/20260803134646.16640-3-sj@kernel.org
Fixes: de3c60e1c8 ("mm/damon: add synchronous commit for commit_inputs")
Signed-off-by: SJ Park <sj@kernel.org>
Cc: Liew Rui Yan <aethernet65535@gmail.com>
Cc: <stable@vger.kernel.org> # 7.2.x
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
SJ Park 2026-08-03 06:46:45 -07:00 committed by Andrew Morton
parent b9b6bad94c
commit 0f18683103
1 changed files with 6 additions and 5 deletions
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11
mm/damon/lru_sort.c
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@ -351,6 +351,8 @@ static int damon_lru_sort_commit_inputs_fn(void *arg)
return damon_lru_sort_apply_parameters();
}
static bool damon_lru_sort_damon_has_started;
static int damon_lru_sort_commit_inputs_store(const char *val,
const struct kernel_param *kp)
{
@ -371,11 +373,8 @@ static int damon_lru_sort_commit_inputs_store(const char *val,
if (!commit_inputs_request)
return 0;
/*
* Skip damon_call() if ctx is not initialized to avoid
* NULL pointer dereference.
*/
if (!ctx)
/* Skip damon_call() if ctx has not successfully started. */
if (!damon_lru_sort_damon_has_started)
return -EINVAL;
err = damon_call(ctx, &control);
@ -426,6 +425,8 @@ static int damon_lru_sort_turn(bool on)
err = damon_start(&ctx, 1, true);
if (err)
return err;
if (!damon_lru_sort_damon_has_started)
damon_lru_sort_damon_has_started = true;
return damon_call(ctx, &call_control);
}