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![Jeff Layton](/assets/img/avatar_default.png)
commited9ab7346e
upstream. Commitf5f9d4a314
("nfsd: move reply cache initialization into nfsd startup") moved the initialization of the reply cache into nfsd startup, but didn't account for the stats counters, which can be accessed before nfsd is ever started. The result can be a NULL pointer dereference when someone accesses /proc/fs/nfsd/reply_cache_stats while nfsd is still shut down. This is a regression and a user-triggerable oops in the right situation: - non-x86_64 arch - /proc/fs/nfsd is mounted in the namespace - nfsd is not started in the namespace - unprivileged user calls "cat /proc/fs/nfsd/reply_cache_stats" Although this is easy to trigger on some arches (like aarch64), on x86_64, calling this_cpu_ptr(NULL) evidently returns a pointer to the fixed_percpu_data. That struct looks just enough like a newly initialized percpu var to allow nfsd_reply_cache_stats_show to access it without Oopsing. Move the initialization of the per-net+per-cpu reply-cache counters back into nfsd_init_net, while leaving the rest of the reply cache allocations to be done at nfsd startup time. Kudos to Eirik who did most of the legwork to track this down. Cc: stable@vger.kernel.org # v6.3+ Fixes:f5f9d4a314
("nfsd: move reply cache initialization into nfsd startup") Reported-and-tested-by: Eirik Fuller <efuller@redhat.com> Closes: https://bugzilla.redhat.com/show_bug.cgi?id=2215429 Signed-off-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
632 lines
17 KiB
C
632 lines
17 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Request reply cache. This is currently a global cache, but this may
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* change in the future and be a per-client cache.
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*
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* This code is heavily inspired by the 44BSD implementation, although
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* it does things a bit differently.
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*
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* Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
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*/
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#include <linux/sunrpc/svc_xprt.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <linux/sunrpc/addr.h>
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#include <linux/highmem.h>
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#include <linux/log2.h>
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#include <linux/hash.h>
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#include <net/checksum.h>
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#include "nfsd.h"
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#include "cache.h"
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#include "trace.h"
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/*
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* We use this value to determine the number of hash buckets from the max
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* cache size, the idea being that when the cache is at its maximum number
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* of entries, then this should be the average number of entries per bucket.
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*/
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#define TARGET_BUCKET_SIZE 64
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struct nfsd_drc_bucket {
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struct rb_root rb_head;
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struct list_head lru_head;
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spinlock_t cache_lock;
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};
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static struct kmem_cache *drc_slab;
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static int nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *vec);
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static unsigned long nfsd_reply_cache_count(struct shrinker *shrink,
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struct shrink_control *sc);
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static unsigned long nfsd_reply_cache_scan(struct shrinker *shrink,
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struct shrink_control *sc);
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/*
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* Put a cap on the size of the DRC based on the amount of available
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* low memory in the machine.
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*
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* 64MB: 8192
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* 128MB: 11585
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* 256MB: 16384
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* 512MB: 23170
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* 1GB: 32768
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* 2GB: 46340
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* 4GB: 65536
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* 8GB: 92681
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* 16GB: 131072
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*
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* ...with a hard cap of 256k entries. In the worst case, each entry will be
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* ~1k, so the above numbers should give a rough max of the amount of memory
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* used in k.
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*
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* XXX: these limits are per-container, so memory used will increase
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* linearly with number of containers. Maybe that's OK.
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*/
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static unsigned int
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nfsd_cache_size_limit(void)
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{
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unsigned int limit;
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unsigned long low_pages = totalram_pages() - totalhigh_pages();
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limit = (16 * int_sqrt(low_pages)) << (PAGE_SHIFT-10);
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return min_t(unsigned int, limit, 256*1024);
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}
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/*
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* Compute the number of hash buckets we need. Divide the max cachesize by
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* the "target" max bucket size, and round up to next power of two.
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*/
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static unsigned int
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nfsd_hashsize(unsigned int limit)
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{
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return roundup_pow_of_two(limit / TARGET_BUCKET_SIZE);
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}
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static struct svc_cacherep *
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nfsd_reply_cache_alloc(struct svc_rqst *rqstp, __wsum csum,
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struct nfsd_net *nn)
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{
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struct svc_cacherep *rp;
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rp = kmem_cache_alloc(drc_slab, GFP_KERNEL);
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if (rp) {
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rp->c_state = RC_UNUSED;
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rp->c_type = RC_NOCACHE;
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RB_CLEAR_NODE(&rp->c_node);
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INIT_LIST_HEAD(&rp->c_lru);
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memset(&rp->c_key, 0, sizeof(rp->c_key));
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rp->c_key.k_xid = rqstp->rq_xid;
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rp->c_key.k_proc = rqstp->rq_proc;
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rpc_copy_addr((struct sockaddr *)&rp->c_key.k_addr, svc_addr(rqstp));
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rpc_set_port((struct sockaddr *)&rp->c_key.k_addr, rpc_get_port(svc_addr(rqstp)));
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rp->c_key.k_prot = rqstp->rq_prot;
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rp->c_key.k_vers = rqstp->rq_vers;
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rp->c_key.k_len = rqstp->rq_arg.len;
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rp->c_key.k_csum = csum;
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}
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return rp;
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}
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static void
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nfsd_reply_cache_free_locked(struct nfsd_drc_bucket *b, struct svc_cacherep *rp,
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struct nfsd_net *nn)
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{
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if (rp->c_type == RC_REPLBUFF && rp->c_replvec.iov_base) {
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nfsd_stats_drc_mem_usage_sub(nn, rp->c_replvec.iov_len);
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kfree(rp->c_replvec.iov_base);
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}
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if (rp->c_state != RC_UNUSED) {
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rb_erase(&rp->c_node, &b->rb_head);
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list_del(&rp->c_lru);
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atomic_dec(&nn->num_drc_entries);
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nfsd_stats_drc_mem_usage_sub(nn, sizeof(*rp));
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}
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kmem_cache_free(drc_slab, rp);
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}
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static void
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nfsd_reply_cache_free(struct nfsd_drc_bucket *b, struct svc_cacherep *rp,
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struct nfsd_net *nn)
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{
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spin_lock(&b->cache_lock);
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nfsd_reply_cache_free_locked(b, rp, nn);
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spin_unlock(&b->cache_lock);
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}
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int nfsd_drc_slab_create(void)
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{
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drc_slab = kmem_cache_create("nfsd_drc",
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sizeof(struct svc_cacherep), 0, 0, NULL);
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return drc_slab ? 0: -ENOMEM;
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}
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void nfsd_drc_slab_free(void)
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{
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kmem_cache_destroy(drc_slab);
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}
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/**
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* nfsd_net_reply_cache_init - per net namespace reply cache set-up
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* @nn: nfsd_net being initialized
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*
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* Returns zero on succes; otherwise a negative errno is returned.
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*/
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int nfsd_net_reply_cache_init(struct nfsd_net *nn)
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{
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return nfsd_percpu_counters_init(nn->counter, NFSD_NET_COUNTERS_NUM);
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}
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/**
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* nfsd_net_reply_cache_destroy - per net namespace reply cache tear-down
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* @nn: nfsd_net being freed
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*
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*/
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void nfsd_net_reply_cache_destroy(struct nfsd_net *nn)
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{
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nfsd_percpu_counters_destroy(nn->counter, NFSD_NET_COUNTERS_NUM);
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}
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int nfsd_reply_cache_init(struct nfsd_net *nn)
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{
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unsigned int hashsize;
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unsigned int i;
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int status = 0;
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nn->max_drc_entries = nfsd_cache_size_limit();
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atomic_set(&nn->num_drc_entries, 0);
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hashsize = nfsd_hashsize(nn->max_drc_entries);
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nn->maskbits = ilog2(hashsize);
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nn->nfsd_reply_cache_shrinker.scan_objects = nfsd_reply_cache_scan;
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nn->nfsd_reply_cache_shrinker.count_objects = nfsd_reply_cache_count;
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nn->nfsd_reply_cache_shrinker.seeks = 1;
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status = register_shrinker(&nn->nfsd_reply_cache_shrinker,
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"nfsd-reply:%s", nn->nfsd_name);
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if (status)
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return status;
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nn->drc_hashtbl = kvzalloc(array_size(hashsize,
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sizeof(*nn->drc_hashtbl)), GFP_KERNEL);
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if (!nn->drc_hashtbl)
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goto out_shrinker;
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for (i = 0; i < hashsize; i++) {
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INIT_LIST_HEAD(&nn->drc_hashtbl[i].lru_head);
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spin_lock_init(&nn->drc_hashtbl[i].cache_lock);
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}
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nn->drc_hashsize = hashsize;
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return 0;
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out_shrinker:
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unregister_shrinker(&nn->nfsd_reply_cache_shrinker);
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printk(KERN_ERR "nfsd: failed to allocate reply cache\n");
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return -ENOMEM;
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}
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void nfsd_reply_cache_shutdown(struct nfsd_net *nn)
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{
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struct svc_cacherep *rp;
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unsigned int i;
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unregister_shrinker(&nn->nfsd_reply_cache_shrinker);
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for (i = 0; i < nn->drc_hashsize; i++) {
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struct list_head *head = &nn->drc_hashtbl[i].lru_head;
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while (!list_empty(head)) {
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rp = list_first_entry(head, struct svc_cacherep, c_lru);
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nfsd_reply_cache_free_locked(&nn->drc_hashtbl[i],
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rp, nn);
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}
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}
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kvfree(nn->drc_hashtbl);
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nn->drc_hashtbl = NULL;
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nn->drc_hashsize = 0;
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}
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/*
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* Move cache entry to end of LRU list, and queue the cleaner to run if it's
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* not already scheduled.
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*/
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static void
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lru_put_end(struct nfsd_drc_bucket *b, struct svc_cacherep *rp)
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{
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rp->c_timestamp = jiffies;
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list_move_tail(&rp->c_lru, &b->lru_head);
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}
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static noinline struct nfsd_drc_bucket *
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nfsd_cache_bucket_find(__be32 xid, struct nfsd_net *nn)
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{
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unsigned int hash = hash_32((__force u32)xid, nn->maskbits);
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return &nn->drc_hashtbl[hash];
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}
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static long prune_bucket(struct nfsd_drc_bucket *b, struct nfsd_net *nn,
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unsigned int max)
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{
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struct svc_cacherep *rp, *tmp;
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long freed = 0;
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list_for_each_entry_safe(rp, tmp, &b->lru_head, c_lru) {
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/*
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* Don't free entries attached to calls that are still
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* in-progress, but do keep scanning the list.
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*/
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if (rp->c_state == RC_INPROG)
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continue;
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if (atomic_read(&nn->num_drc_entries) <= nn->max_drc_entries &&
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time_before(jiffies, rp->c_timestamp + RC_EXPIRE))
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break;
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nfsd_reply_cache_free_locked(b, rp, nn);
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if (max && freed++ > max)
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break;
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}
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return freed;
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}
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static long nfsd_prune_bucket(struct nfsd_drc_bucket *b, struct nfsd_net *nn)
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{
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return prune_bucket(b, nn, 3);
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}
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/*
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* Walk the LRU list and prune off entries that are older than RC_EXPIRE.
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* Also prune the oldest ones when the total exceeds the max number of entries.
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*/
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static long
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prune_cache_entries(struct nfsd_net *nn)
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{
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unsigned int i;
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long freed = 0;
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for (i = 0; i < nn->drc_hashsize; i++) {
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struct nfsd_drc_bucket *b = &nn->drc_hashtbl[i];
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if (list_empty(&b->lru_head))
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continue;
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spin_lock(&b->cache_lock);
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freed += prune_bucket(b, nn, 0);
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spin_unlock(&b->cache_lock);
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}
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return freed;
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}
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static unsigned long
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nfsd_reply_cache_count(struct shrinker *shrink, struct shrink_control *sc)
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{
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struct nfsd_net *nn = container_of(shrink,
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struct nfsd_net, nfsd_reply_cache_shrinker);
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return atomic_read(&nn->num_drc_entries);
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}
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static unsigned long
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nfsd_reply_cache_scan(struct shrinker *shrink, struct shrink_control *sc)
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{
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struct nfsd_net *nn = container_of(shrink,
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struct nfsd_net, nfsd_reply_cache_shrinker);
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return prune_cache_entries(nn);
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}
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/*
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* Walk an xdr_buf and get a CRC for at most the first RC_CSUMLEN bytes
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*/
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static __wsum
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nfsd_cache_csum(struct svc_rqst *rqstp)
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{
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int idx;
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unsigned int base;
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__wsum csum;
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struct xdr_buf *buf = &rqstp->rq_arg;
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const unsigned char *p = buf->head[0].iov_base;
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size_t csum_len = min_t(size_t, buf->head[0].iov_len + buf->page_len,
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RC_CSUMLEN);
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size_t len = min(buf->head[0].iov_len, csum_len);
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/* rq_arg.head first */
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csum = csum_partial(p, len, 0);
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csum_len -= len;
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/* Continue into page array */
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idx = buf->page_base / PAGE_SIZE;
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base = buf->page_base & ~PAGE_MASK;
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while (csum_len) {
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p = page_address(buf->pages[idx]) + base;
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len = min_t(size_t, PAGE_SIZE - base, csum_len);
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csum = csum_partial(p, len, csum);
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csum_len -= len;
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base = 0;
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++idx;
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}
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return csum;
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}
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static int
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nfsd_cache_key_cmp(const struct svc_cacherep *key,
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const struct svc_cacherep *rp, struct nfsd_net *nn)
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{
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if (key->c_key.k_xid == rp->c_key.k_xid &&
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key->c_key.k_csum != rp->c_key.k_csum) {
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nfsd_stats_payload_misses_inc(nn);
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trace_nfsd_drc_mismatch(nn, key, rp);
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}
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return memcmp(&key->c_key, &rp->c_key, sizeof(key->c_key));
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}
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/*
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* Search the request hash for an entry that matches the given rqstp.
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* Must be called with cache_lock held. Returns the found entry or
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* inserts an empty key on failure.
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*/
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static struct svc_cacherep *
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nfsd_cache_insert(struct nfsd_drc_bucket *b, struct svc_cacherep *key,
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struct nfsd_net *nn)
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{
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struct svc_cacherep *rp, *ret = key;
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struct rb_node **p = &b->rb_head.rb_node,
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*parent = NULL;
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unsigned int entries = 0;
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int cmp;
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while (*p != NULL) {
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++entries;
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parent = *p;
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rp = rb_entry(parent, struct svc_cacherep, c_node);
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cmp = nfsd_cache_key_cmp(key, rp, nn);
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if (cmp < 0)
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p = &parent->rb_left;
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else if (cmp > 0)
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p = &parent->rb_right;
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else {
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ret = rp;
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goto out;
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}
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}
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rb_link_node(&key->c_node, parent, p);
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rb_insert_color(&key->c_node, &b->rb_head);
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out:
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/* tally hash chain length stats */
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if (entries > nn->longest_chain) {
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nn->longest_chain = entries;
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nn->longest_chain_cachesize = atomic_read(&nn->num_drc_entries);
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} else if (entries == nn->longest_chain) {
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/* prefer to keep the smallest cachesize possible here */
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nn->longest_chain_cachesize = min_t(unsigned int,
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nn->longest_chain_cachesize,
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atomic_read(&nn->num_drc_entries));
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}
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lru_put_end(b, ret);
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return ret;
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}
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/**
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* nfsd_cache_lookup - Find an entry in the duplicate reply cache
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* @rqstp: Incoming Call to find
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*
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* Try to find an entry matching the current call in the cache. When none
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* is found, we try to grab the oldest expired entry off the LRU list. If
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* a suitable one isn't there, then drop the cache_lock and allocate a
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* new one, then search again in case one got inserted while this thread
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* didn't hold the lock.
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*
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* Return values:
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* %RC_DOIT: Process the request normally
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* %RC_REPLY: Reply from cache
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* %RC_DROPIT: Do not process the request further
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*/
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int nfsd_cache_lookup(struct svc_rqst *rqstp)
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{
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struct nfsd_net *nn;
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struct svc_cacherep *rp, *found;
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__wsum csum;
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struct nfsd_drc_bucket *b;
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int type = rqstp->rq_cachetype;
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int rtn = RC_DOIT;
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rqstp->rq_cacherep = NULL;
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if (type == RC_NOCACHE) {
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nfsd_stats_rc_nocache_inc();
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goto out;
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}
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csum = nfsd_cache_csum(rqstp);
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/*
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* Since the common case is a cache miss followed by an insert,
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* preallocate an entry.
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*/
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nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
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rp = nfsd_reply_cache_alloc(rqstp, csum, nn);
|
|
if (!rp)
|
|
goto out;
|
|
|
|
b = nfsd_cache_bucket_find(rqstp->rq_xid, nn);
|
|
spin_lock(&b->cache_lock);
|
|
found = nfsd_cache_insert(b, rp, nn);
|
|
if (found != rp)
|
|
goto found_entry;
|
|
|
|
nfsd_stats_rc_misses_inc();
|
|
rqstp->rq_cacherep = rp;
|
|
rp->c_state = RC_INPROG;
|
|
|
|
atomic_inc(&nn->num_drc_entries);
|
|
nfsd_stats_drc_mem_usage_add(nn, sizeof(*rp));
|
|
|
|
nfsd_prune_bucket(b, nn);
|
|
|
|
out_unlock:
|
|
spin_unlock(&b->cache_lock);
|
|
out:
|
|
return rtn;
|
|
|
|
found_entry:
|
|
/* We found a matching entry which is either in progress or done. */
|
|
nfsd_reply_cache_free_locked(NULL, rp, nn);
|
|
nfsd_stats_rc_hits_inc();
|
|
rtn = RC_DROPIT;
|
|
rp = found;
|
|
|
|
/* Request being processed */
|
|
if (rp->c_state == RC_INPROG)
|
|
goto out_trace;
|
|
|
|
/* From the hall of fame of impractical attacks:
|
|
* Is this a user who tries to snoop on the cache? */
|
|
rtn = RC_DOIT;
|
|
if (!test_bit(RQ_SECURE, &rqstp->rq_flags) && rp->c_secure)
|
|
goto out_trace;
|
|
|
|
/* Compose RPC reply header */
|
|
switch (rp->c_type) {
|
|
case RC_NOCACHE:
|
|
break;
|
|
case RC_REPLSTAT:
|
|
xdr_stream_encode_be32(&rqstp->rq_res_stream, rp->c_replstat);
|
|
rtn = RC_REPLY;
|
|
break;
|
|
case RC_REPLBUFF:
|
|
if (!nfsd_cache_append(rqstp, &rp->c_replvec))
|
|
goto out_unlock; /* should not happen */
|
|
rtn = RC_REPLY;
|
|
break;
|
|
default:
|
|
WARN_ONCE(1, "nfsd: bad repcache type %d\n", rp->c_type);
|
|
}
|
|
|
|
out_trace:
|
|
trace_nfsd_drc_found(nn, rqstp, rtn);
|
|
goto out_unlock;
|
|
}
|
|
|
|
/**
|
|
* nfsd_cache_update - Update an entry in the duplicate reply cache.
|
|
* @rqstp: svc_rqst with a finished Reply
|
|
* @cachetype: which cache to update
|
|
* @statp: pointer to Reply's NFS status code, or NULL
|
|
*
|
|
* This is called from nfsd_dispatch when the procedure has been
|
|
* executed and the complete reply is in rqstp->rq_res.
|
|
*
|
|
* We're copying around data here rather than swapping buffers because
|
|
* the toplevel loop requires max-sized buffers, which would be a waste
|
|
* of memory for a cache with a max reply size of 100 bytes (diropokres).
|
|
*
|
|
* If we should start to use different types of cache entries tailored
|
|
* specifically for attrstat and fh's, we may save even more space.
|
|
*
|
|
* Also note that a cachetype of RC_NOCACHE can legally be passed when
|
|
* nfsd failed to encode a reply that otherwise would have been cached.
|
|
* In this case, nfsd_cache_update is called with statp == NULL.
|
|
*/
|
|
void nfsd_cache_update(struct svc_rqst *rqstp, int cachetype, __be32 *statp)
|
|
{
|
|
struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
|
|
struct svc_cacherep *rp = rqstp->rq_cacherep;
|
|
struct kvec *resv = &rqstp->rq_res.head[0], *cachv;
|
|
struct nfsd_drc_bucket *b;
|
|
int len;
|
|
size_t bufsize = 0;
|
|
|
|
if (!rp)
|
|
return;
|
|
|
|
b = nfsd_cache_bucket_find(rp->c_key.k_xid, nn);
|
|
|
|
len = resv->iov_len - ((char*)statp - (char*)resv->iov_base);
|
|
len >>= 2;
|
|
|
|
/* Don't cache excessive amounts of data and XDR failures */
|
|
if (!statp || len > (256 >> 2)) {
|
|
nfsd_reply_cache_free(b, rp, nn);
|
|
return;
|
|
}
|
|
|
|
switch (cachetype) {
|
|
case RC_REPLSTAT:
|
|
if (len != 1)
|
|
printk("nfsd: RC_REPLSTAT/reply len %d!\n",len);
|
|
rp->c_replstat = *statp;
|
|
break;
|
|
case RC_REPLBUFF:
|
|
cachv = &rp->c_replvec;
|
|
bufsize = len << 2;
|
|
cachv->iov_base = kmalloc(bufsize, GFP_KERNEL);
|
|
if (!cachv->iov_base) {
|
|
nfsd_reply_cache_free(b, rp, nn);
|
|
return;
|
|
}
|
|
cachv->iov_len = bufsize;
|
|
memcpy(cachv->iov_base, statp, bufsize);
|
|
break;
|
|
case RC_NOCACHE:
|
|
nfsd_reply_cache_free(b, rp, nn);
|
|
return;
|
|
}
|
|
spin_lock(&b->cache_lock);
|
|
nfsd_stats_drc_mem_usage_add(nn, bufsize);
|
|
lru_put_end(b, rp);
|
|
rp->c_secure = test_bit(RQ_SECURE, &rqstp->rq_flags);
|
|
rp->c_type = cachetype;
|
|
rp->c_state = RC_DONE;
|
|
spin_unlock(&b->cache_lock);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Copy cached reply to current reply buffer. Should always fit.
|
|
* FIXME as reply is in a page, we should just attach the page, and
|
|
* keep a refcount....
|
|
*/
|
|
static int
|
|
nfsd_cache_append(struct svc_rqst *rqstp, struct kvec *data)
|
|
{
|
|
struct kvec *vec = &rqstp->rq_res.head[0];
|
|
|
|
if (vec->iov_len + data->iov_len > PAGE_SIZE) {
|
|
printk(KERN_WARNING "nfsd: cached reply too large (%zd).\n",
|
|
data->iov_len);
|
|
return 0;
|
|
}
|
|
memcpy((char*)vec->iov_base + vec->iov_len, data->iov_base, data->iov_len);
|
|
vec->iov_len += data->iov_len;
|
|
return 1;
|
|
}
|
|
|
|
/*
|
|
* Note that fields may be added, removed or reordered in the future. Programs
|
|
* scraping this file for info should test the labels to ensure they're
|
|
* getting the correct field.
|
|
*/
|
|
int nfsd_reply_cache_stats_show(struct seq_file *m, void *v)
|
|
{
|
|
struct nfsd_net *nn = net_generic(file_inode(m->file)->i_sb->s_fs_info,
|
|
nfsd_net_id);
|
|
|
|
seq_printf(m, "max entries: %u\n", nn->max_drc_entries);
|
|
seq_printf(m, "num entries: %u\n",
|
|
atomic_read(&nn->num_drc_entries));
|
|
seq_printf(m, "hash buckets: %u\n", 1 << nn->maskbits);
|
|
seq_printf(m, "mem usage: %lld\n",
|
|
percpu_counter_sum_positive(&nn->counter[NFSD_NET_DRC_MEM_USAGE]));
|
|
seq_printf(m, "cache hits: %lld\n",
|
|
percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_RC_HITS]));
|
|
seq_printf(m, "cache misses: %lld\n",
|
|
percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_RC_MISSES]));
|
|
seq_printf(m, "not cached: %lld\n",
|
|
percpu_counter_sum_positive(&nfsdstats.counter[NFSD_STATS_RC_NOCACHE]));
|
|
seq_printf(m, "payload misses: %lld\n",
|
|
percpu_counter_sum_positive(&nn->counter[NFSD_NET_PAYLOAD_MISSES]));
|
|
seq_printf(m, "longest chain len: %u\n", nn->longest_chain);
|
|
seq_printf(m, "cachesize at longest: %u\n", nn->longest_chain_cachesize);
|
|
return 0;
|
|
}
|