From bc2940869508b7b956a757a26d3b1ebf9546790e Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Wed, 23 Oct 2024 16:34:42 -0400 Subject: [PATCH] nfs_common: fix localio to cope with racing nfs_local_probe() Fix the possibility of racing nfs_local_probe() resulting in: list_add double add: new=ffff8b99707f9f58, prev=ffff8b99707f9f58, next=ffffffffc0f30000. ------------[ cut here ]------------ kernel BUG at lib/list_debug.c:35! Add nfs_uuid_init() to properly initialize all nfs_uuid_t members (particularly its list_head). Switch to returning bool from nfs_uuid_begin(), returns false if nfs_uuid_t is already in-use (its list_head is on a list). Update nfs_local_probe() to return early if the nfs_client's cl_uuid (nfs_uuid_t) is in-use. Also, switch nfs_uuid_begin() from using list_add_tail_rcu() to list_add_tail() -- rculist was used in an earlier version of the localio code that had a lockless nfs_uuid_lookup interface. Signed-off-by: Mike Snitzer Signed-off-by: Anna Schumaker --- fs/nfs/client.c | 3 +-- fs/nfs/localio.c | 3 ++- fs/nfs_common/nfslocalio.c | 23 ++++++++++++++++++----- include/linux/nfslocalio.h | 3 ++- 4 files changed, 23 insertions(+), 9 deletions(-) diff --git a/fs/nfs/client.c b/fs/nfs/client.c index 114282398716..03ecc7765615 100644 --- a/fs/nfs/client.c +++ b/fs/nfs/client.c @@ -181,8 +181,7 @@ struct nfs_client *nfs_alloc_client(const struct nfs_client_initdata *cl_init) #if IS_ENABLED(CONFIG_NFS_LOCALIO) seqlock_init(&clp->cl_boot_lock); ktime_get_real_ts64(&clp->cl_nfssvc_boot); - clp->cl_uuid.net = NULL; - clp->cl_uuid.dom = NULL; + nfs_uuid_init(&clp->cl_uuid); spin_lock_init(&clp->cl_localio_lock); #endif /* CONFIG_NFS_LOCALIO */ diff --git a/fs/nfs/localio.c b/fs/nfs/localio.c index d0aa680ec816..8f0ce82a677e 100644 --- a/fs/nfs/localio.c +++ b/fs/nfs/localio.c @@ -205,7 +205,8 @@ void nfs_local_probe(struct nfs_client *clp) nfs_local_disable(clp); } - nfs_uuid_begin(&clp->cl_uuid); + if (!nfs_uuid_begin(&clp->cl_uuid)) + return; if (nfs_server_uuid_is_local(clp)) nfs_local_enable(clp); nfs_uuid_end(&clp->cl_uuid); diff --git a/fs/nfs_common/nfslocalio.c b/fs/nfs_common/nfslocalio.c index 5c8ce5066c16..09404d142d1a 100644 --- a/fs/nfs_common/nfslocalio.c +++ b/fs/nfs_common/nfslocalio.c @@ -5,7 +5,7 @@ */ #include -#include +#include #include #include @@ -20,15 +20,27 @@ static DEFINE_SPINLOCK(nfs_uuid_lock); */ static LIST_HEAD(nfs_uuids); -void nfs_uuid_begin(nfs_uuid_t *nfs_uuid) +void nfs_uuid_init(nfs_uuid_t *nfs_uuid) { nfs_uuid->net = NULL; nfs_uuid->dom = NULL; - uuid_gen(&nfs_uuid->uuid); + INIT_LIST_HEAD(&nfs_uuid->list); +} +EXPORT_SYMBOL_GPL(nfs_uuid_init); +bool nfs_uuid_begin(nfs_uuid_t *nfs_uuid) +{ spin_lock(&nfs_uuid_lock); - list_add_tail_rcu(&nfs_uuid->list, &nfs_uuids); + /* Is this nfs_uuid already in use? */ + if (!list_empty(&nfs_uuid->list)) { + spin_unlock(&nfs_uuid_lock); + return false; + } + uuid_gen(&nfs_uuid->uuid); + list_add_tail(&nfs_uuid->list, &nfs_uuids); spin_unlock(&nfs_uuid_lock); + + return true; } EXPORT_SYMBOL_GPL(nfs_uuid_begin); @@ -36,7 +48,8 @@ void nfs_uuid_end(nfs_uuid_t *nfs_uuid) { if (nfs_uuid->net == NULL) { spin_lock(&nfs_uuid_lock); - list_del_init(&nfs_uuid->list); + if (nfs_uuid->net == NULL) + list_del_init(&nfs_uuid->list); spin_unlock(&nfs_uuid_lock); } } diff --git a/include/linux/nfslocalio.h b/include/linux/nfslocalio.h index b0dd9b1eef4f..3982fea79919 100644 --- a/include/linux/nfslocalio.h +++ b/include/linux/nfslocalio.h @@ -32,7 +32,8 @@ typedef struct { struct auth_domain *dom; /* auth_domain for localio */ } nfs_uuid_t; -void nfs_uuid_begin(nfs_uuid_t *); +void nfs_uuid_init(nfs_uuid_t *); +bool nfs_uuid_begin(nfs_uuid_t *); void nfs_uuid_end(nfs_uuid_t *); void nfs_uuid_is_local(const uuid_t *, struct list_head *, struct net *, struct auth_domain *, struct module *);