From: Chuck Lever <chuck.lever@xxxxxxxxxx> [ Upstream commit aadc3bbea163b6caaaebfdd2b6c4667fbc726752 ] Nothing appears to limit the number of concurrent async COPY operations that clients can start. In addition, AFAICT each async COPY can copy an unlimited number of 4MB chunks, so can run for a long time. Thus IMO async COPY can become a DoS vector. Add a restriction mechanism that bounds the number of concurrent background COPY operations. Start simple and try to be fair -- this patch implements a per-namespace limit. An async COPY request that occurs while this limit is exceeded gets NFS4ERR_DELAY. The requesting client can choose to send the request again after a delay or fall back to a traditional read/write style copy. If there is need to make the mechanism more sophisticated, we can visit that in future patches. Cc: stable@xxxxxxxxxxxxxxx Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx> Link: https://nvd.nist.gov/vuln/detail/CVE-2024-49974 Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/nfsd/netns.h | 1 + fs/nfsd/nfs4proc.c | 11 +++++++++-- fs/nfsd/nfs4state.c | 1 + fs/nfsd/xdr4.h | 1 + 4 files changed, 12 insertions(+), 2 deletions(-) --- a/fs/nfsd/netns.h +++ b/fs/nfsd/netns.h @@ -152,6 +152,7 @@ struct nfsd_net { u32 s2s_cp_cl_id; struct idr s2s_cp_stateids; spinlock_t s2s_cp_lock; + atomic_t pending_async_copies; /* * Version information --- a/fs/nfsd/nfs4proc.c +++ b/fs/nfsd/nfs4proc.c @@ -1244,6 +1244,7 @@ static void nfs4_put_copy(struct nfsd4_c { if (!refcount_dec_and_test(©->refcount)) return; + atomic_dec(©->cp_nn->pending_async_copies); kfree(copy->cp_src); kfree(copy); } @@ -1782,10 +1783,16 @@ nfsd4_copy(struct svc_rqst *rqstp, struc memcpy(©->fh, &cstate->current_fh.fh_handle, sizeof(struct knfsd_fh)); if (nfsd4_copy_is_async(copy)) { - status = nfserrno(-ENOMEM); async_copy = kzalloc(sizeof(struct nfsd4_copy), GFP_KERNEL); if (!async_copy) goto out_err; + async_copy->cp_nn = nn; + /* Arbitrary cap on number of pending async copy operations */ + if (atomic_inc_return(&nn->pending_async_copies) > + (int)rqstp->rq_pool->sp_nrthreads) { + atomic_dec(&nn->pending_async_copies); + goto out_err; + } INIT_LIST_HEAD(&async_copy->copies); refcount_set(&async_copy->refcount, 1); async_copy->cp_src = kmalloc(sizeof(*async_copy->cp_src), GFP_KERNEL); @@ -1824,7 +1831,7 @@ out_err: } if (async_copy) cleanup_async_copy(async_copy); - status = nfserrno(-ENOMEM); + status = nfserr_jukebox; goto out; } --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -8088,6 +8088,7 @@ static int nfs4_state_create_net(struct spin_lock_init(&nn->client_lock); spin_lock_init(&nn->s2s_cp_lock); idr_init(&nn->s2s_cp_stateids); + atomic_set(&nn->pending_async_copies, 0); spin_lock_init(&nn->blocked_locks_lock); INIT_LIST_HEAD(&nn->blocked_locks_lru); --- a/fs/nfsd/xdr4.h +++ b/fs/nfsd/xdr4.h @@ -574,6 +574,7 @@ struct nfsd4_copy { struct nfsd4_ssc_umount_item *ss_nsui; struct nfs_fh c_fh; nfs4_stateid stateid; + struct nfsd_net *cp_nn; }; static inline void nfsd4_copy_set_sync(struct nfsd4_copy *copy, bool sync) Patches currently in stable-queue which might be from cel@xxxxxxxxxx are queue-5.10/nfsd-never-decrement-pending_async_copies-on-error.patch queue-5.10/nfsd-limit-the-number-of-concurrent-async-copy-operations.patch queue-5.10/nfsd-initialize-struct-nfsd4_copy-earlier.patch queue-5.10/nfsd-async-copy-result-needs-to-return-a-write-verifier.patch queue-5.10/nfsd-initialize-copy-cp_clp-early-in-nfsd4_copy-for-use-by-trace-point.patch
