ovl: fix use after free in struct ovl_aio_req

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Example for triggering use after free in a overlay on ext4 setup:

aio_read
  ovl_read_iter
    vfs_iter_read
      ext4_file_read_iter
        ext4_dio_read_iter
          iomap_dio_rw -> -EIOCBQUEUED
          /*
	   * Here IO is completed in a separate thread,
	   * ovl_aio_cleanup_handler() frees aio_req which has iocb embedded
	   */
          file_accessed(iocb->ki_filp); /**BOOM**/

Fix by introducing a refcount in ovl_aio_req similarly to aio_kiocb.  This
guarantees that iocb is only freed after vfs_read/write_iter() returns on
underlying fs.

Fixes: 2406a307ac ("ovl: implement async IO routines")
Signed-off-by: yangerkun <yangerkun@huawei.com>
Link: https://lore.kernel.org/r/20210930032228.3199690-3-yangerkun@huawei.com/
Cc: <stable@vger.kernel.org> # v5.6
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

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yangerkun 2021-09-30 11:22:28 +08:00 • committed by Miklos Szeredi

parent 1dc1eed46f

commit 9a25440376

1 changed files with 14 additions and 2 deletions

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fs/overlayfs/file.c

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