From: Jan Kara <jack@suse.cz>
To: Ted Tso <tytso@mit.edu>
Cc: <linux-ext4@vger.kernel.org>, <linux-fsdevel@vger.kernel.org>,
Eric Sandeen <sandeen@sandeen.net>, Jan Kara <jack@suse.cz>
Subject: [PATCH 1/3] fs: Avoid leaving freed inode on dirty list
Date: Tue, 21 Apr 2020 10:54:43 +0200 [thread overview]
Message-ID: <20200421085445.5731-2-jack@suse.cz> (raw)
In-Reply-To: <20200421085445.5731-1-jack@suse.cz>
evict() can race with writeback_sb_inodes() and so
list_empty(&inode->i_io_list) check can race with list_move() from
redirty_tail() possibly resulting in list_empty() returning false and
thus we end up leaving freed inode in wb->b_dirty list leading to
use-after-free issues.
Fix the problem by using list_empty_careful() check and add assert that
inode's i_io_list is empty in clear_inode() to catch the problem earlier
in the future.
Signed-off-by: Jan Kara <jack@suse.cz>
---
fs/inode.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/fs/inode.c b/fs/inode.c
index 93d9252a00ab..a73c8a7aa71a 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -534,6 +534,7 @@ void clear_inode(struct inode *inode)
BUG_ON(!(inode->i_state & I_FREEING));
BUG_ON(inode->i_state & I_CLEAR);
BUG_ON(!list_empty(&inode->i_wb_list));
+ BUG_ON(!list_empty(&inode->i_io_list));
/* don't need i_lock here, no concurrent mods to i_state */
inode->i_state = I_FREEING | I_CLEAR;
}
@@ -559,7 +560,13 @@ static void evict(struct inode *inode)
BUG_ON(!(inode->i_state & I_FREEING));
BUG_ON(!list_empty(&inode->i_lru));
- if (!list_empty(&inode->i_io_list))
+ /*
+ * We are the only holder of the inode so it cannot be marked dirty.
+ * Flusher thread won't start new writeback but there can be still e.g.
+ * redirty_tail() running from writeback_sb_inodes(). So we have to be
+ * careful to remove inode from dirty/io list in all the cases.
+ */
+ if (!list_empty_careful(&inode->i_io_list))
inode_io_list_del(inode);
inode_sb_list_del(inode);
--
2.16.4
next prev parent reply other threads:[~2020-04-21 8:54 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-21 8:54 ext4: Fix use after free issues with journalled data Jan Kara
2020-04-21 8:54 ` Jan Kara [this message]
2020-04-25 6:42 ` [PATCH 1/3] fs: Avoid leaving freed inode on dirty list Xiaoguang Wang
2020-04-27 10:05 ` Jan Kara
2020-04-21 8:54 ` [PATCH 2/3] writeback: Export inode_io_list_del() Jan Kara
2020-05-14 14:57 ` Theodore Y. Ts'o
2020-04-21 8:54 ` [PATCH 3/3] ext4: Avoid freeing inodes on dirty list Jan Kara
2020-05-14 14:57 ` Theodore Y. Ts'o
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