[PATCH 5.16 0911/1017] ubifs: Fix ui->dirty race between do_tmpfile() and writeback work

Greg Kroah-Hartman
2022-04-05T10:27:43Z

From: Zhihao Cheng <chengzhihao1@huawei.com>

commit 60eb3b9c9f11206996f57cb89521824304b305ad upstream.

'ui->dirty' is not protected by 'ui_mutex' in function do_tmpfile() which
may race with ubifs_write_inode[wb_workfn] to access/update 'ui->dirty',
finally dirty space is released twice.

open(O_TMPFILE) wb_workfn
do_tmpfile
ubifs_budget_space(ino_req = { .dirtied_ino = 1})
d_tmpfile // mark inode(tmpfile) dirty
ubifs_jnl_update // without holding tmpfile's ui_mutex
mark_inode_clean(ui)
if (ui->dirty)
ubifs_release_dirty_inode_budget(ui) // release first time
ubifs_write_inode
mutex_lock(&ui->ui_mutex)
ubifs_release_dirty_inode_budget(ui)
// release second time
mutex_unlock(&ui->ui_mutex)
ui->dirty = 0

Run generic/476 can reproduce following message easily
(See reproducer in [Link]):

UBIFS error (ubi0:0 pid 2578): ubifs_assert_failed [ubifs]: UBIFS assert
failed: c->bi.dd_growth >= 0, in fs/ubifs/budget.c:554
UBIFS warning (ubi0:0 pid 2578): ubifs_ro_mode [ubifs]: switched to
read-only mode, error -22
Workqueue: writeback wb_workfn (flush-ubifs_0_0)
Call Trace:
ubifs_ro_mode+0x54/0x60 [ubifs]
ubifs_assert_failed+0x4b/0x80 [ubifs]
ubifs_release_budget+0x468/0x5a0 [ubifs]
ubifs_release_dirty_inode_budget+0x53/0x80 [ubifs]
ubifs_write_inode+0x121/0x1f0 [ubifs]
...
wb_workfn+0x283/0x7b0

Fix it by holding tmpfile ubifs inode lock during ubifs_jnl_update().
Similar problem exists in whiteout renaming, but previous fix("ubifs:
Rename whiteout atomically") has solved the problem.

Fixes: 474b93704f32163 ("ubifs: Implement O_TMPFILE")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=214765
Signed-off-by: Zhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/ubifs/dir.c | 60 ++++++++++++++++++++++++++++-----------------------------
1 file changed, 30 insertions(+), 30 deletions(-)

--- a/fs/ubifs/dir.c
+++ b/fs/ubifs/dir.c
@@ -397,6 +397,32 @@ out_free:
return ERR_PTR(err);
}

+/**
+ * lock_2_inodes - a wrapper for locking two UBIFS inodes.
+ * @inode1: first inode
+ * @inode2: second inode
+ *
+ * We do not implement any tricks to guarantee strict lock ordering, because
+ * VFS has already done it for us on the @i_mutex. So this is just a simple
+ * wrapper function.
+ */
+static void lock_2_inodes(struct inode *inode1, struct inode *inode2)
+{
+ mutex_lock_nested(&ubifs_inode(inode1)->ui_mutex, WB_MUTEX_1);
+ mutex_lock_nested(&ubifs_inode(inode2)->ui_mutex, WB_MUTEX_2);
+}
+
+/**
+ * unlock_2_inodes - a wrapper for unlocking two UBIFS inodes.
+ * @inode1: first inode
+ * @inode2: second inode
+ */
+static void unlock_2_inodes(struct inode *inode1, struct inode *inode2)
+{
+ mutex_unlock(&ubifs_inode(inode2)->ui_mutex);
+ mutex_unlock(&ubifs_inode(inode1)->ui_mutex);
+}
+
static int ubifs_tmpfile(struct user_namespace *mnt_userns, struct inode *dir,
struct dentry *dentry, umode_t mode)
{
@@ -404,7 +430,7 @@ static int ubifs_tmpfile(struct user_nam
struct ubifs_info *c = dir->i_sb->s_fs_info;
struct ubifs_budget_req req = { .new_ino = 1, .new_dent = 1};
struct ubifs_budget_req ino_req = { .dirtied_ino = 1 };
- struct ubifs_inode *ui, *dir_ui = ubifs_inode(dir);
+ struct ubifs_inode *ui;
int err, instantiated = 0;
struct fscrypt_name nm;

@@ -452,18 +478,18 @@ static int ubifs_tmpfile(struct user_nam
instantiated = 1;
mutex_unlock(&ui->ui_mutex);

- mutex_lock(&dir_ui->ui_mutex);
+ lock_2_inodes(dir, inode);
err = ubifs_jnl_update(c, dir, &nm, inode, 1, 0);
if (err)
goto out_cancel;
- mutex_unlock(&dir_ui->ui_mutex);
+ unlock_2_inodes(dir, inode);

ubifs_release_budget(c, &req);

return 0;

out_cancel:
- mutex_unlock(&dir_ui->ui_mutex);
+ unlock_2_inodes(dir, inode);
out_inode:
make_bad_inode(inode);
if (!instantiated)
@@ -690,32 +716,6 @@ static int ubifs_dir_release(struct inod
return 0;
}

-/**
- * lock_2_inodes - a wrapper for locking two UBIFS inodes.
- * @inode1: first inode
- * @inode2: second inode
- *
- * We do not implement any tricks to guarantee strict lock ordering, because
- * VFS has already done it for us on the @i_mutex. So this is just a simple
- * wrapper function.
- */
-static void lock_2_inodes(struct inode *inode1, struct inode *inode2)
-{
- mutex_lock_nested(&ubifs_inode(inode1)->ui_mutex, WB_MUTEX_1);
- mutex_lock_nested(&ubifs_inode(inode2)->ui_mutex, WB_MUTEX_2);
-}
-
-/**
- * unlock_2_inodes - a wrapper for unlocking two UBIFS inodes.
- * @inode1: first inode
- * @inode2: second inode
- */
-static void unlock_2_inodes(struct inode *inode1, struct inode *inode2)
-{
- mutex_unlock(&ubifs_inode(inode2)->ui_mutex);
- mutex_unlock(&ubifs_inode(inode1)->ui_mutex);
-}
-
static int ubifs_link(struct dentry *old_dentry, struct inode *dir,
struct dentry *dentry)
{