mirrors/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2024-09-27 12:57:53 +00:00
Code Issues Releases Wiki Activity

cifs: Fix potential deadlock when updating vol in cifs_reconnect()

Browse source 
commit 06d57378bc upstream.

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>
Signed-off-by: Rishabh Bhatnagar <risbhat@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Paulo Alcantara (SUSE) 2023-06-23 21:34:06 +00:00 committed by Greg Kroah-Hartman
parent 8a5aaa4562
commit be178a5eae
1 changed files with 77 additions and 32 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

109
fs/cifs/dfs_cache.c
View file

@ -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 @@ int dfs_cache_add_vol(char *mntdata, struct smb_vol *vol, const char *fullpath)
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 @@ static void refresh_tcon(struct vol_info *vi, struct cifs_tcon *tcon)
*/
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);
}