ovl: fortify ovl_copy_xattr() against underlying layer modifications

Adapt ovl_getxattr_value() to be used from ovl_copy_xattr(), by
allowing to pass it a pre-allocated buffer, which can be resized
and by handling the ENODATA/EOPNOTSUPP return codes in the caller.

This replaces the retry loop in ovl_copy_xattr() with a single retry
after resizing the buffer. If the value changed again by then, the
underlying layer was modified, so return -EIO instead of retrying.

As a side effect, ovl_copy_up_meta_inode_data() now returns -EIO instead
of -ERANGE in this case of underlying xattr size changes.

Reported-by: Fahad Alharbi <fahad@codepure.com>
Tested-by: Fahad Alharbi <fahad@codepure.com>
Suggested-by: Miklos Szeredi <miklos@szeredi.hu>
Link: https://lore.kernel.org/linux-fsdevel/CAJfpegsVoUyqy0dYkTvBGRZvgdv_nmzmCw_uF+LP-Vq3EhEkSg@mail.gmail.com/
Fixes: e4ad29fa0d22 ("ovl: use a minimal buffer in ovl_copy_xattr")
Cc: stable@vger.kernel.org
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

0 files changed, 0 insertions, 0 deletions