twx-linux

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Zheng Liang 9d4969d8b5 ovl: fix missing negative dentry check in ovl_rename()

commit a295aef603 upstream.

The following reproducer

  mkdir lower upper work merge
  touch lower/old
  touch lower/new
  mount -t overlay overlay -olowerdir=lower,upperdir=upper,workdir=work merge
  rm merge/new
  mv merge/old merge/new & unlink upper/new

may result in this race:

PROCESS A:
  rename("merge/old", "merge/new");
  overwrite=true,ovl_lower_positive(old)=true,
  ovl_dentry_is_whiteout(new)=true -> flags |= RENAME_EXCHANGE

PROCESS B:
  unlink("upper/new");

PROCESS A:
  lookup newdentry in new_upperdir
  call vfs_rename() with negative newdentry and RENAME_EXCHANGE

Fix by adding the missing check for negative newdentry.

Signed-off-by: Zheng Liang <zhengliang6@huawei.com>
Fixes: e9be9d5e76 ("overlay filesystem")
Cc: <stable@vger.kernel.org> # v3.18
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2021-10-13 10:10:50 +02:00

copy_up.c

ovl: fix missing revert_creds() on error path

2021-05-22 10:59:26 +02:00

dir.c

ovl: fix missing negative dentry check in ovl_rename()

2021-10-13 10:10:50 +02:00

export.c

ovl: relax WARN_ON() when decoding lower directory file handle

2020-07-22 09:32:10 +02:00

file.c

ovl: fix unneeded call to ovl_change_flags()