6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jeff Layton [ Upstream commit bbf13732f74351d21c5e0e8dd9bd8e1c48dc35d4 ] nfsd_file_dispose_list_delayed() defers fput() to nfsd service threads via a per-net freeme queue, preventing the shrinker and GC worker from bearing the cost of closing files (see ffb402596147). However, the queue lives in a separately-allocated struct nfsd_fcache_disposal that is freed by nfsd_free_fcache_disposal_net() during per-net teardown. The global shrinker, laundrette, and fsnotify callbacks can still be inside nfsd_file_dispose_list_delayed() dereferencing that pointer, causing a use-after-free. Inline the spinlock and freeme list directly into struct nfsd_net (as fcache_dispose_lock and fcache_dispose_list), eliminating the separately allocated struct nfsd_fcache_disposal entirely. These fields now have the same lifetime as the net namespace itself, so there is no dangling pointer to chase. nfsd_file_cache_start_net() now just initializes the inline fields and cannot fail due to allocation. nfsd_file_cache_shutdown_net() drains the inline list directly instead of freeing a separate struct. The alloc/free helpers are removed. Fixes: 1463b38e7cf3 ("NFSD: simplify per-net file cache management") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-opus-4-6 Signed-off-by: Jeff Layton Link: https://patch.msgid.link/20260602-nfsd-testing-v2-7-e4ea62e3cd5c@kernel.org Signed-off-by: Chuck Lever Signed-off-by: Sasha Levin --- fs/nfsd/filecache.c | 74 +++++++++++++++------------------------------ fs/nfsd/netns.h | 4 ++- 2 files changed, 27 insertions(+), 51 deletions(-) diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c index 7d8ad34127d33..c3ce0c100446e 100644 --- a/fs/nfsd/filecache.c +++ b/fs/nfsd/filecache.c @@ -60,12 +60,6 @@ static DEFINE_PER_CPU(unsigned long, nfsd_file_releases); static DEFINE_PER_CPU(unsigned long, nfsd_file_total_age); static DEFINE_PER_CPU(unsigned long, nfsd_file_evictions); -struct nfsd_fcache_disposal { - struct work_struct work; - spinlock_t lock; - struct list_head freeme; -}; - static struct workqueue_struct *nfsd_filecache_wq __read_mostly; static struct kmem_cache *nfsd_file_slab; @@ -417,12 +411,11 @@ nfsd_file_dispose_list_delayed(struct list_head *dispose) struct nfsd_file *nf = list_first_entry(dispose, struct nfsd_file, nf_gc); struct nfsd_net *nn = net_generic(nf->nf_net, nfsd_net_id); - struct nfsd_fcache_disposal *l = nn->fcache_disposal; - spin_lock(&l->lock); - list_move_tail(&nf->nf_gc, &l->freeme); - spin_unlock(&l->lock); - queue_work(nfsd_filecache_wq, &l->work); + spin_lock(&nn->fcache_dispose_lock); + list_move_tail(&nf->nf_gc, &nn->fcache_dispose_list); + spin_unlock(&nn->fcache_dispose_lock); + queue_work(nfsd_filecache_wq, &nn->fcache_dispose_work); } } @@ -651,12 +644,12 @@ static void nfsd_file_delayed_close(struct work_struct *work) { LIST_HEAD(head); - struct nfsd_fcache_disposal *l = container_of(work, - struct nfsd_fcache_disposal, work); + struct nfsd_net *nn = container_of(work, struct nfsd_net, + fcache_dispose_work); - spin_lock(&l->lock); - list_splice_init(&l->freeme, &head); - spin_unlock(&l->lock); + spin_lock(&nn->fcache_dispose_lock); + list_splice_init(&nn->fcache_dispose_list, &head); + spin_unlock(&nn->fcache_dispose_lock); nfsd_file_dispose_list(&head); } @@ -825,44 +818,22 @@ __nfsd_file_cache_purge(struct net *net) nfsd_file_dispose_list(&dispose); } -static struct nfsd_fcache_disposal * -nfsd_alloc_fcache_disposal(void) -{ - struct nfsd_fcache_disposal *l; - - l = kmalloc(sizeof(*l), GFP_KERNEL); - if (!l) - return NULL; - INIT_WORK(&l->work, nfsd_file_delayed_close); - spin_lock_init(&l->lock); - INIT_LIST_HEAD(&l->freeme); - return l; -} - -static void -nfsd_free_fcache_disposal(struct nfsd_fcache_disposal *l) -{ - cancel_work_sync(&l->work); - nfsd_file_dispose_list(&l->freeme); - kfree(l); -} - -static void -nfsd_free_fcache_disposal_net(struct net *net) -{ - struct nfsd_net *nn = net_generic(net, nfsd_net_id); - struct nfsd_fcache_disposal *l = nn->fcache_disposal; - - nfsd_free_fcache_disposal(l); -} - int nfsd_file_cache_start_net(struct net *net) { struct nfsd_net *nn = net_generic(net, nfsd_net_id); - nn->fcache_disposal = nfsd_alloc_fcache_disposal(); - return nn->fcache_disposal ? 0 : -ENOMEM; + /* + * The dispose state lives as long as the net namespace and may still + * be reached by the shrinker after a previous shutdown, so only + * initialize it once. + */ + if (!nn->fcache_dispose_work.func) { + INIT_WORK(&nn->fcache_dispose_work, nfsd_file_delayed_close); + spin_lock_init(&nn->fcache_dispose_lock); + INIT_LIST_HEAD(&nn->fcache_dispose_list); + } + return 0; } /** @@ -881,8 +852,11 @@ nfsd_file_cache_purge(struct net *net) void nfsd_file_cache_shutdown_net(struct net *net) { + struct nfsd_net *nn = net_generic(net, nfsd_net_id); + nfsd_file_cache_purge(net); - nfsd_free_fcache_disposal_net(net); + cancel_work_sync(&nn->fcache_dispose_work); + nfsd_file_dispose_list(&nn->fcache_dispose_list); } void diff --git a/fs/nfsd/netns.h b/fs/nfsd/netns.h index 443b7d2368f38..798f66da05365 100644 --- a/fs/nfsd/netns.h +++ b/fs/nfsd/netns.h @@ -211,7 +211,9 @@ struct nfsd_net { /* utsname taken from the process that starts the server */ char nfsd_name[UNX_MAXNODENAME+1]; - struct nfsd_fcache_disposal *fcache_disposal; + spinlock_t fcache_dispose_lock; + struct list_head fcache_dispose_list; + struct work_struct fcache_dispose_work; siphash_key_t siphash_key; -- 2.53.0