From: SeongJae Park sj@kernel.org Subject: mm/damon/dbgfs: fix 'struct pid' leaks in 'dbgfs_target_ids_write()'

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.

Link: https://lkml.kernel.org/r/20211229124029.23348-1-sj@kernel.org 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+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/damon/dbgfs.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)

--- a/mm/damon/dbgfs.c~mm-damon-dbgfs-fix-struct-pid-leaks-in-dbgfs_target_ids_write +++ a/mm/damon/dbgfs.c @@ -353,6 +353,7 @@ static ssize_t dbgfs_target_ids_write(st 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; @@ -397,8 +398,12 @@ static ssize_t dbgfs_target_ids_write(st 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) _