[PATCH 5.15 200/279] mm/damon/dbgfs: fix missed use of damon_dbgfs_lock

Greg Kroah-Hartman
2021-11-24T13:58:17Z

From: SeongJae Park <sj@kernel.org>

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>
---
mm/damon/dbgfs.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -538,12 +538,14 @@ static ssize_t dbgfs_monitor_on_write(st
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(voi

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;
}