[PATCH 4.9 21/54] ep_create_wakeup_source(): dentry name can change under you...

From: Greg Kroah-Hartman
Date: Mon Oct 12 2020 - 10:05:35 EST


From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

commit 3701cb59d892b88d569427586f01491552f377b1 upstream.

or get freed, for that matter, if it's a long (separately stored)
name.

Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
fs/eventpoll.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1260,7 +1260,7 @@ static int reverse_path_check(void)

static int ep_create_wakeup_source(struct epitem *epi)
{
- const char *name;
+ struct name_snapshot n;
struct wakeup_source *ws;

if (!epi->ep->ws) {
@@ -1269,8 +1269,9 @@ static int ep_create_wakeup_source(struc
return -ENOMEM;
}

- name = epi->ffd.file->f_path.dentry->d_name.name;
- ws = wakeup_source_register(name);
+ take_dentry_name_snapshot(&n, epi->ffd.file->f_path.dentry);
+ ws = wakeup_source_register(n.name);
+ release_dentry_name_snapshot(&n);

if (!ws)
return -ENOMEM;