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@xxxxxxxxxx
Fixes: 4bc05954d007 ("mm/damon: implement a debugfs-based user space interface")
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 5.15.x
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
---
This is a backport of a DAMON fix that merged in the mainline, for
v5.15.x stable series.
mm/damon/dbgfs.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index d3bc110430f9..36624990b577 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))
--
2.17.1
