Updated answer:
President Putin addressed this issue in a press conference around 16:45 UTC on February 22nd:
As for the borders, within what borders will we recognize these
republics. We recognized them, which means we recognized their
constitutions. And the constitutions spelled out the borders within
the Donetsk and Luhansk regions - at the time when they were part of
Ukraine.
This means that, according to Putin, Russia recognises the territory of the LPR & DPR to include all of the yellow-shaded territory in the map below, courtesy of the New York Times. This represents the entirety of the Luhansk and Donetsk Oblasts, including territory currently controlled by Ukraine.

Original answer follows:
It's not currently clear - the decrees signed by President Putin, "On the recognition of the Donetsk People's Republic" and "On the recognition of the Luhansk People's Republic" don't refer to territorial claims, and there have been several contradicting answers from Russian officials.
Article 7 of both treaties as ratified by the State Duma (Luhansk, Donetsk) state:
The Contracting Parties confirm and respect the territorial integrity
and inviolability of the existing borders of the Russian Federation
and the [Luhansk People's Republic / Donetsk People's Republic]. The Parties shall conclude a
separate agreement on the State border between the Russian Federation
and the [Luhansk People's Republic / Donetsk People's Republic]. The protection of the State border
of the [Luhansk People's Republic / Donetsk People's Republic] shall be carried out jointly by the
Contracting Parties in the interests of their own security and peace
and stability. The Contracting Parties will conclude a separate
agreement on this matter.
This lines up with the statement to Rossiyskaya Gazeta by the spokeswoman for the Ministry of Foreign Affairs, Maria Zakharova, who said that "the issue of the borders of the LPR and the DPR would be resolved after the ratification of the friendship treaty".
The Deputy Foreign Minister, Andrei Rudenko, however, responded to a question from Interfax, stating that the recognised borders are "the borders within which the DPR and LPR leaderships operate and have jurisdiction".
On the other hand, in a press briefing held by Putin's press secretary, Dmitry Peskov, he initially defined the extent of territorial recognition as being "within the borders that they have proclaimed themselves", but didn't not expand on this when questioned. Meduza.io carries the transcript of the conference:
CNN: Regarding the recognition of the sovereignty of the DNR and LNR,
tell me, are we talking about recognizing them in their current, de
facto borders or within the borders of the entire Luhansk and Donetsk
regions? As we understand it, these are a bit different.
Dmitry Peskov: Within the borders that they have proclaimed
themselves.
CNN: Proclaimed at what point?
Dmitry Peskov: Well, when these two republics were proclaimed.
Bloomberg: Can you elaborate on this issue?
Dmitry Peskov: No, I have nothing to add.
Ekho Moskvy: Do these borders include Mariupol, for example?
Dmitry Peskov: I have nothing to add to this. Within the borders in
which they exist and have been proclaimed.
Ekho Moskvy: In which they exist or were proclaimed?
Dmitry Peskov: Well, in which they were proclaimed and exist.
Ekho Moskvy: Meaning, within the current borders?
Dmitry Peskov: I have nothing to add to this.
BBC News: Can you clarify? I don’t quite understand: Will the
recognition of the people’s republics mean the borders that exist now
or those that they’ve proclaimed themselves?
Dmitry Peskov: Within the borders in which these republics were
proclaimed.
BBC News: In 2014? Meaning, the entire Donetsk and Luhansk regions?
Dmitry Peskov: In this case, I’ve said everything I can on this
subject.