On Sun, 2022-07-31 at 13:19 -0700, Dai Ngo wrote:
> 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@xxxxxxxxxx>
> ---
> fs/nfsd/nfs4state.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 9409a0dc1b76..749f51dff5c7 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -6608,6 +6608,7 @@ 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);
> @@ -6616,6 +6617,8 @@ 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);
Nice catch.
There are a number of places that call free_ol_stateid_reaplist. Is it
really only in nfsd4_close_open_stateid that we need to do this? I
wonder if it would be better to do this inside free_ol_stateid_reaplist
instead so that all of those callers clean up the copy states as well?
--
Jeff Layton <jlayton@xxxxxxxxxx>
