DAMON debugfs interface increases the reference counts of 'struct pid's for targets from the 'target_ids' file write callback ('dbgfs_target_ids_write()'), but decreases the counts only in DAMON monitoring termination callback ('dbgfs_before_terminate()'). Therefore, when 'target_ids' file is repeatedly written without DAMON monitoring start/termination, the reference count is not decreased and therefore memory for the 'struct pid' cannot be freed. This commit fixes this issue by decreasing the reference counts when 'target_ids' is written.

Fixes: 4bc05954d007 ("mm/damon: implement a debugfs-based user space interface") Signed-off-by: SeongJae Park sj@kernel.org Cc: stable@vger.kernel.org # 5.15.x --- mm/damon/dbgfs.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c index 489be9c830c4..751c7b835684 100644 --- a/mm/damon/dbgfs.c +++ b/mm/damon/dbgfs.c @@ -362,6 +362,7 @@ static ssize_t dbgfs_target_ids_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { struct damon_ctx *ctx = file->private_data; + struct damon_target *t, *next_t; bool id_is_pid = true; char *kbuf, *nrs; unsigned long *targets; @@ -406,8 +407,12 @@ static ssize_t dbgfs_target_ids_write(struct file *file, goto unlock_out; }

- /* remove targets with previously-set primitive */ - damon_set_targets(ctx, NULL, 0); + /* remove previously set targets */ + damon_for_each_target_safe(t, next_t, ctx) { + if (targetid_is_pid(ctx)) + put_pid((struct pid *)t->id); + damon_destroy_target(t); + }

/* Configure the context for the address space type */ if (id_is_pid)