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Code Issues Releases Wiki Activity

ubifs: Fix 'ui->dirty' race between do_tmpfile() and writeback work 

'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: 474b93704f ("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>
This commit is contained in:
Zhihao Cheng 2021-12-27 11:22:37 +08:00 committed by Richard Weinberger
parent 278d9a2436
commit 60eb3b9c9f
1 changed files with 30 additions and 30 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

60
fs/ubifs/dir.c
View File

@ -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_namespace *mnt_userns, struct inode *dir,
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_namespace *mnt_userns, struct inode *dir,
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 inode *dir, struct file *file)
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)
{