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authorPaulo Alcantara (SUSE) <pc@cjr.nz>2019-12-04 17:38:02 -0300
committerSteve French <stfrench@microsoft.com>2020-01-26 19:24:16 -0600
commit06d57378bcc9b2c33640945174842115593795d1 (patch)
treebcb8b54174a3b4c3ed19ddf49ec95768950250c7 /fs/cifs
parentcifs: Merge is_path_valid() into get_normalized_path() (diff)
downloadlinux-dev-06d57378bcc9b2c33640945174842115593795d1.tar.xz
linux-dev-06d57378bcc9b2c33640945174842115593795d1.zip
cifs: Fix potential deadlock when updating vol in cifs_reconnect()
We can't acquire volume lock while refreshing the DFS cache because cifs_reconnect() may call dfs_cache_update_vol() while we are walking through the volume list. To prevent that, make vol_info refcounted, create a temp list with all volumes eligible for refreshing, and then use it without any locks held. Besides, replace vol_lock with a spinlock and protect cache_ttl from concurrent accesses or changes. Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz> Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to 'fs/cifs')
-rw-r--r--fs/cifs/dfs_cache.c109
1 files changed, 77 insertions, 32 deletions
diff --git a/fs/cifs/dfs_cache.c b/fs/cifs/dfs_cache.c
index 1d1f7c03931b..82c5d9a31f9e 100644
--- a/fs/cifs/dfs_cache.c
+++ b/fs/cifs/dfs_cache.c
@@ -49,15 +49,20 @@ struct cache_entry {
struct vol_info {
char *fullpath;
+ spinlock_t smb_vol_lock;
struct smb_vol smb_vol;
char *mntdata;
struct list_head list;
+ struct list_head rlist;
+ struct kref refcnt;
};
static struct kmem_cache *cache_slab __read_mostly;
static struct workqueue_struct *dfscache_wq __read_mostly;
static int cache_ttl;
+static DEFINE_SPINLOCK(cache_ttl_lock);
+
static struct nls_table *cache_nlsc;
/*
@@ -69,7 +74,7 @@ static struct hlist_head cache_htable[CACHE_HTABLE_SIZE];
static DEFINE_MUTEX(list_lock);
static LIST_HEAD(vol_list);
-static DEFINE_MUTEX(vol_lock);
+static DEFINE_SPINLOCK(vol_list_lock);
static void refresh_cache_worker(struct work_struct *work);
@@ -300,7 +305,6 @@ int dfs_cache_init(void)
for (i = 0; i < CACHE_HTABLE_SIZE; i++)
INIT_HLIST_HEAD(&cache_htable[i]);
- cache_ttl = -1;
cache_nlsc = load_nls_default();
cifs_dbg(FYI, "%s: initialized DFS referral cache\n", __func__);
@@ -471,15 +475,15 @@ add_cache_entry(unsigned int hash, const char *path,
hlist_add_head_rcu(&ce->hlist, &cache_htable[hash]);
- mutex_lock(&vol_lock);
- if (cache_ttl < 0) {
+ spin_lock(&cache_ttl_lock);
+ if (!cache_ttl) {
cache_ttl = ce->ttl;
queue_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ);
} else {
cache_ttl = min_t(int, cache_ttl, ce->ttl);
mod_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ);
}
- mutex_unlock(&vol_lock);
+ spin_unlock(&cache_ttl_lock);
return ce;
}
@@ -523,21 +527,32 @@ static inline void destroy_slab_cache(void)
kmem_cache_destroy(cache_slab);
}
-static inline void free_vol(struct vol_info *vi)
+static void __vol_release(struct vol_info *vi)
{
- list_del(&vi->list);
kfree(vi->fullpath);
kfree(vi->mntdata);
cifs_cleanup_volume_info_contents(&vi->smb_vol);
kfree(vi);
}
+static void vol_release(struct kref *kref)
+{
+ struct vol_info *vi = container_of(kref, struct vol_info, refcnt);
+
+ spin_lock(&vol_list_lock);
+ list_del(&vi->list);
+ spin_unlock(&vol_list_lock);
+ __vol_release(vi);
+}
+
static inline void free_vol_list(void)
{
struct vol_info *vi, *nvi;
- list_for_each_entry_safe(vi, nvi, &vol_list, list)
- free_vol(vi);
+ list_for_each_entry_safe(vi, nvi, &vol_list, list) {
+ list_del_init(&vi->list);
+ __vol_release(vi);
+ }
}
/**
@@ -1156,10 +1171,13 @@ int dfs_cache_add_vol(char *mntdata, struct smb_vol *vol, const char *fullpath)
goto err_free_fullpath;
vi->mntdata = mntdata;
+ spin_lock_init(&vi->smb_vol_lock);
+ kref_init(&vi->refcnt);
- mutex_lock(&vol_lock);
+ spin_lock(&vol_list_lock);
list_add_tail(&vi->list, &vol_list);
- mutex_unlock(&vol_lock);
+ spin_unlock(&vol_list_lock);
+
return 0;
err_free_fullpath:
@@ -1169,7 +1187,8 @@ err_free_vi:
return rc;
}
-static inline struct vol_info *find_vol(const char *fullpath)
+/* Must be called with vol_list_lock held */
+static struct vol_info *find_vol(const char *fullpath)
{
struct vol_info *vi;
@@ -1191,7 +1210,6 @@ static inline struct vol_info *find_vol(const char *fullpath)
*/
int dfs_cache_update_vol(const char *fullpath, struct TCP_Server_Info *server)
{
- int rc;
struct vol_info *vi;
if (!fullpath || !server)
@@ -1199,22 +1217,24 @@ int dfs_cache_update_vol(const char *fullpath, struct TCP_Server_Info *server)
cifs_dbg(FYI, "%s: fullpath: %s\n", __func__, fullpath);
- mutex_lock(&vol_lock);
-
+ spin_lock(&vol_list_lock);
vi = find_vol(fullpath);
if (IS_ERR(vi)) {
- rc = PTR_ERR(vi);
- goto out;
+ spin_unlock(&vol_list_lock);
+ return PTR_ERR(vi);
}
+ kref_get(&vi->refcnt);
+ spin_unlock(&vol_list_lock);
cifs_dbg(FYI, "%s: updating volume info\n", __func__);
+ spin_lock(&vi->smb_vol_lock);
memcpy(&vi->smb_vol.dstaddr, &server->dstaddr,
sizeof(vi->smb_vol.dstaddr));
- rc = 0;
+ spin_unlock(&vi->smb_vol_lock);
-out:
- mutex_unlock(&vol_lock);
- return rc;
+ kref_put(&vi->refcnt, vol_release);
+
+ return 0;
}
/**
@@ -1231,11 +1251,11 @@ void dfs_cache_del_vol(const char *fullpath)
cifs_dbg(FYI, "%s: fullpath: %s\n", __func__, fullpath);
- mutex_lock(&vol_lock);
+ spin_lock(&vol_list_lock);
vi = find_vol(fullpath);
- if (!IS_ERR(vi))
- free_vol(vi);
- mutex_unlock(&vol_lock);
+ spin_unlock(&vol_list_lock);
+
+ kref_put(&vi->refcnt, vol_release);
}
/* Get all tcons that are within a DFS namespace and can be refreshed */
@@ -1449,27 +1469,52 @@ out:
*/
static void refresh_cache_worker(struct work_struct *work)
{
- struct vol_info *vi;
+ struct vol_info *vi, *nvi;
struct TCP_Server_Info *server;
- LIST_HEAD(list);
+ LIST_HEAD(vols);
+ LIST_HEAD(tcons);
struct cifs_tcon *tcon, *ntcon;
- mutex_lock(&vol_lock);
-
+ /*
+ * Find SMB volumes that are eligible (server->tcpStatus == CifsGood)
+ * for refreshing.
+ */
+ spin_lock(&vol_list_lock);
list_for_each_entry(vi, &vol_list, list) {
server = get_tcp_server(&vi->smb_vol);
if (!server)
continue;
- get_tcons(server, &list);
- list_for_each_entry_safe(tcon, ntcon, &list, ulist) {
+ kref_get(&vi->refcnt);
+ list_add_tail(&vi->rlist, &vols);
+ put_tcp_server(server);
+ }
+ spin_unlock(&vol_list_lock);
+
+ /* Walk through all TCONs and refresh any expired cache entry */
+ list_for_each_entry_safe(vi, nvi, &vols, rlist) {
+ spin_lock(&vi->smb_vol_lock);
+ server = get_tcp_server(&vi->smb_vol);
+ spin_unlock(&vi->smb_vol_lock);
+
+ if (!server)
+ goto next_vol;
+
+ get_tcons(server, &tcons);
+ list_for_each_entry_safe(tcon, ntcon, &tcons, ulist) {
refresh_tcon(vi, tcon);
list_del_init(&tcon->ulist);
cifs_put_tcon(tcon);
}
put_tcp_server(server);
+
+next_vol:
+ list_del_init(&vi->rlist);
+ kref_put(&vi->refcnt, vol_release);
}
+
+ spin_lock(&cache_ttl_lock);
queue_delayed_work(dfscache_wq, &refresh_task, cache_ttl * HZ);
- mutex_unlock(&vol_lock);
+ spin_unlock(&cache_ttl_lock);
}