[PATCH AUTOSEL 5.15 12/14] writeback: Add asserts for adding freed inode to lists

Sasha Levin
2022-12-24T01:37:27Z

From: Jan Kara <jack@suse.cz>

[ Upstream commit a9438b44bc7015b18931e312bbd249a25bb59a65 ]

In the past we had several use-after-free issues with inodes getting
added to writeback lists after evict() removed them. These are painful
to debug so add some asserts to catch the problem earlier. The only
non-obvious change in the commit is that we need to tweak
redirty_tail_locked() to avoid triggering assertion in
inode_io_list_move_locked().

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20221212113633.29181-1-jack@suse.cz
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/fs-writeback.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index f4a5a0c2858a..0f747eb7706a 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -121,6 +121,7 @@ static bool inode_io_list_move_locked(struct inode *inode,
{
assert_spin_locked(&wb->list_lock);
assert_spin_locked(&inode->i_lock);
+ WARN_ON_ONCE(inode->i_state & I_FREEING);

list_move(&inode->i_io_list, head);

@@ -280,6 +281,7 @@ static void inode_cgwb_move_to_attached(struct inode *inode,
{
assert_spin_locked(&wb->list_lock);
assert_spin_locked(&inode->i_lock);
+ WARN_ON_ONCE(inode->i_state & I_FREEING);

inode->i_state &= ~I_SYNC_QUEUED;
if (wb != &wb->bdi->wb)
@@ -1164,6 +1166,7 @@ static void inode_cgwb_move_to_attached(struct inode *inode,
{
assert_spin_locked(&wb->list_lock);
assert_spin_locked(&inode->i_lock);
+ WARN_ON_ONCE(inode->i_state & I_FREEING);

inode->i_state &= ~I_SYNC_QUEUED;
list_del_init(&inode->i_io_list);
@@ -1329,6 +1332,17 @@ static void redirty_tail_locked(struct inode *inode, struct bdi_writeback *wb)
{
assert_spin_locked(&inode->i_lock);

+ inode->i_state &= ~I_SYNC_QUEUED;
+ /*
+ * When the inode is being freed just don't bother with dirty list
+ * tracking. Flush worker will ignore this inode anyway and it will
+ * trigger assertions in inode_io_list_move_locked().
+ */
+ if (inode->i_state & I_FREEING) {
+ list_del_init(&inode->i_io_list);
+ wb_io_lists_depopulated(wb);
+ return;
+ }
if (!list_empty(&wb->b_dirty)) {
struct inode *tail;

@@ -1337,7 +1351,6 @@ static void redirty_tail_locked(struct inode *inode, struct bdi_writeback *wb)
inode->dirtied_when = jiffies;
}
inode_io_list_move_locked(inode, wb, &wb->b_dirty);
- inode->i_state &= ~I_SYNC_QUEUED;
}

static void redirty_tail(struct inode *inode, struct bdi_writeback *wb)
--
2.35.1