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mm/damon/dbgfs: fix 'struct pid' leaks in 'dbgfs_target_ids_write()'

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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: 4bc05954d0 ("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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
SeongJae Park 2021-12-30 20:12:34 -08:00 committed by Linus Torvalds
parent f5c7329718
commit ebb3f994dd
1 changed files with 7 additions and 2 deletions
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9
mm/damon/dbgfs.c
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@ -353,6 +353,7 @@ 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;
@ -397,8 +398,12 @@ 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)