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    Subject[PATCH 5.15 414/530] NFSD: fix use-after-free on source server when doing inter-server copy
    Date
    From: Dai Ngo <dai.ngo@oracle.com>

    [ Upstream commit 019805fea91599b22dfa62ffb29c022f35abeb06 ]

    Use-after-free occurred when the laundromat tried to free expired
    cpntf_state entry on the s2s_cp_stateids list after inter-server
    copy completed. The sc_cp_list that the expired copy state was
    inserted on was already freed.

    When COPY completes, the Linux client normally sends LOCKU(lock_state x),
    FREE_STATEID(lock_state x) and CLOSE(open_state y) to the source server.
    The nfs4_put_stid call from nfsd4_free_stateid cleans up the copy state
    from the s2s_cp_stateids list before freeing the lock state's stid.

    However, sometimes the CLOSE was sent before the FREE_STATEID request.
    When this happens, the nfsd4_close_open_stateid call from nfsd4_close
    frees all lock states on its st_locks list without cleaning up the copy
    state on the sc_cp_list list. When the time the FREE_STATEID arrives the
    server returns BAD_STATEID since the lock state was freed. This causes
    the use-after-free error to occur when the laundromat tries to free
    the expired cpntf_state.

    This patch adds a call to nfs4_free_cpntf_statelist in
    nfsd4_close_open_stateid to clean up the copy state before calling
    free_ol_stateid_reaplist to free the lock state's stid on the reaplist.

    Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
    Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    fs/nfsd/nfs4state.c | 5 +++++
    1 file changed, 5 insertions(+)

    diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
    index f9e2fa9cfbec..7b763f146b62 100644
    --- a/fs/nfsd/nfs4state.c
    +++ b/fs/nfsd/nfs4state.c
    @@ -961,6 +961,7 @@ static struct nfs4_ol_stateid * nfs4_alloc_open_stateid(struct nfs4_client *clp)

    static void nfs4_free_deleg(struct nfs4_stid *stid)
    {
    + WARN_ON(!list_empty(&stid->sc_cp_list));
    kmem_cache_free(deleg_slab, stid);
    atomic_long_dec(&num_delegations);
    }
    @@ -1374,6 +1375,7 @@ static void nfs4_free_ol_stateid(struct nfs4_stid *stid)
    release_all_access(stp);
    if (stp->st_stateowner)
    nfs4_put_stateowner(stp->st_stateowner);
    + WARN_ON(!list_empty(&stid->sc_cp_list));
    kmem_cache_free(stateid_slab, stid);
    }

    @@ -6389,6 +6391,7 @@ static void nfsd4_close_open_stateid(struct nfs4_ol_stateid *s)
    struct nfs4_client *clp = s->st_stid.sc_client;
    bool unhashed;
    LIST_HEAD(reaplist);
    + struct nfs4_ol_stateid *stp;

    spin_lock(&clp->cl_lock);
    unhashed = unhash_open_stateid(s, &reaplist);
    @@ -6397,6 +6400,8 @@ static void nfsd4_close_open_stateid(struct nfs4_ol_stateid *s)
    if (unhashed)
    put_ol_stateid_locked(s, &reaplist);
    spin_unlock(&clp->cl_lock);
    + list_for_each_entry(stp, &reaplist, st_locks)
    + nfs4_free_cpntf_statelist(clp->net, &stp->st_stid);
    free_ol_stateid_reaplist(&reaplist);
    } else {
    spin_unlock(&clp->cl_lock);
    --
    2.35.1


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