mm/damon/dbgfs: fix missed use of damon_dbgfs_lock

commit d78f3853f831eee46c6dbe726debf3be9e9c0d05 upstream.

DAMON debugfs is supposed to protect dbgfs_ctxs, dbgfs_nr_ctxs, and
dbgfs_dirs using damon_dbgfs_lock.  However, some of the code is
accessing the variables without the protection.  This fixes it by
protecting all such accesses.

Link: https://lkml.kernel.org/r/20211110145758.16558-3-sj@kernel.org
Fixes: 75c1c2b53c78 ("mm/damon/dbgfs: support multiple contexts")
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index 2741ff79e8e84e14dede482c37856620ac468045..f94d19a690dfacd445e9c3225b8ff41c826f313f 100644 (file)
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -538,12 +538,14 @@ static ssize_t dbgfs_monitor_on_write(struct file *file,
                return -EINVAL;
        }
 
+       mutex_lock(&damon_dbgfs_lock);
        if (!strncmp(kbuf, "on", count))
                err = damon_start(dbgfs_ctxs, dbgfs_nr_ctxs);
        else if (!strncmp(kbuf, "off", count))
                err = damon_stop(dbgfs_ctxs, dbgfs_nr_ctxs);
        else
                err = -EINVAL;
+       mutex_unlock(&damon_dbgfs_lock);
 
        if (err)
                ret = err;
@@ -596,15 +598,16 @@ static int __init __damon_dbgfs_init(void)
 
 static int __init damon_dbgfs_init(void)
 {
-       int rc;
+       int rc = -ENOMEM;
 
+       mutex_lock(&damon_dbgfs_lock);
        dbgfs_ctxs = kmalloc(sizeof(*dbgfs_ctxs), GFP_KERNEL);
        if (!dbgfs_ctxs)
-               return -ENOMEM;
+               goto out;
        dbgfs_ctxs[0] = dbgfs_new_ctx();
        if (!dbgfs_ctxs[0]) {
                kfree(dbgfs_ctxs);
-               return -ENOMEM;
+               goto out;
        }
        dbgfs_nr_ctxs = 1;
 
@@ -615,6 +618,8 @@ static int __init damon_dbgfs_init(void)
                pr_err("%s: dbgfs init failed\n", __func__);
        }
 
+out:
+       mutex_unlock(&damon_dbgfs_lock);
        return rc;
 }