lkml.org 
[lkml]   [2021]   [Jun]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 4.9 07/71] gfs2: Fix use-after-free in gfs2_glock_shrink_scan
Date
From: Hillf Danton <hdanton@sina.com>

[ Upstream commit 1ab19c5de4c537ec0d9b21020395a5b5a6c059b2 ]

The GLF_LRU flag is checked under lru_lock in gfs2_glock_remove_from_lru() to
remove the glock from the lru list in __gfs2_glock_put().

On the shrink scan path, the same flag is cleared under lru_lock but because
of cond_resched_lock(&lru_lock) in gfs2_dispose_glock_lru(), progress on the
put side can be made without deleting the glock from the lru list.

Keep GLF_LRU across the race window opened by cond_resched_lock(&lru_lock) to
ensure correct behavior on both sides - clear GLF_LRU after list_del under
lru_lock.

Reported-by: syzbot <syzbot+34ba7ddbf3021981a228@syzkaller.appspotmail.com>
Signed-off-by: Hillf Danton <hdanton@sina.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/gfs2/glock.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
index f19e49a5d032..3d4d35083438 100644
--- a/fs/gfs2/glock.c
+++ b/fs/gfs2/glock.c
@@ -1350,6 +1350,7 @@ __acquires(&lru_lock)
while(!list_empty(list)) {
gl = list_entry(list->next, struct gfs2_glock, gl_lru);
list_del_init(&gl->gl_lru);
+ clear_bit(GLF_LRU, &gl->gl_flags);
if (!spin_trylock(&gl->gl_lockref.lock)) {
add_back_to_lru:
list_add(&gl->gl_lru, &lru_list);
@@ -1396,7 +1397,6 @@ static long gfs2_scan_glock_lru(int nr)
if (!test_bit(GLF_LOCK, &gl->gl_flags)) {
list_move(&gl->gl_lru, &dispose);
atomic_dec(&lru_count);
- clear_bit(GLF_LRU, &gl->gl_flags);
freed++;
continue;
}
--
2.30.2
\
 
 \ /
  Last update: 2021-06-28 17:20    [W:0.831 / U:1.448 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site