From ffe4a1ba1a82c416a6b3a09d46594f6a885ae141 Mon Sep 17 00:00:00 2001 From: SeongJae Park Date: Thu, 30 Dec 2021 20:12:34 -0800 Subject: [PATCH] mm/damon/dbgfs: fix 'struct pid' leaks in 'dbgfs_target_ids_write()' commit ebb3f994dd92f8fb4d70c7541091216c1e10cb71 upstream. 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 Cc: [5.15+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/damon/dbgfs.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c index d3bc110430f9d..36624990b5777 100644 --- a/mm/damon/dbgfs.c +++ b/mm/damon/dbgfs.c @@ -185,6 +185,7 @@ 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; char *kbuf, *nrs; unsigned long *targets; ssize_t nr_targets; @@ -224,6 +225,13 @@ static ssize_t dbgfs_target_ids_write(struct file *file, goto unlock_out; } + /* 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); + } + err = damon_set_targets(ctx, targets, nr_targets); if (err) { if (targetid_is_pid(ctx))