[PATCH] revlog: ensure that flags do not overflow 2 bytes

[Gregory Szorc]

On Fri, Nov 25, 2016 at 5:24 AM, Cotizo Sima <cotizo at fb.com> wrote:

> # HG changeset patch
> # User Cotizo Sima <cotizo at fb.com>
> # Date 1480079985 28800
> #      Fri Nov 25 05:19:45 2016 -0800
> # Node ID 4b311b730614941db6409f560ab9451bec74be75
> # Parent  a3163433647108b7bec8fc45896db1c20b18ab21
> revlog: ensure that flags do not overflow 2 bytes
>
> This patch adds a line that ensures we are not setting by mistake a set of
> flags
> overlfowing the 2 bytes they are allocated. Given the way the data is
> packed in
> the revlog header, overflowing 2 bytes will result in setting a wrong
> offset.
>
> diff --git a/mercurial/revlog.py b/mercurial/revlog.py
> --- a/mercurial/revlog.py
> +++ b/mercurial/revlog.py
> @@ -72,6 +72,7 @@
>      return int(q & 0xFFFF)
>
>  def offset_type(offset, type):
> +    type &= 0xFFFF
>      return long(long(offset) << 16 | type)
>
>  _nullhash = hashlib.sha1(nullid)
>
>
I'm a believer in failing fast. If this new code comes into play, we've
already lost to a bug. I think instead we should raise ValueError if type >
65535.
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