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authorLinus Torvalds <torvalds@linux-foundation.org>2017-01-15 16:09:50 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-01-15 16:09:50 -0800
commit99421c1cb27fb837e93b517036fab4500fe39de5 (patch)
treede5fc5bacb671223f389793ad643cebe520bc292
parentc92816275674c1491ce228ee49aa030a5fa1be04 (diff)
parent93362fa47fe98b62e4a34ab408c4a418432e7939 (diff)
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull namespace fixes from Eric Biederman: "This tree contains 4 fixes. The first is a fix for a race that can causes oopses under the right circumstances, and that someone just recently encountered. Past that are several small trivial correct fixes. A real issue that was blocking development of an out of tree driver, but does not appear to have caused any actual problems for in-tree code. A potential deadlock that was reported by lockdep. And a deadlock people have experienced and took the time to track down caused by a cleanup that removed the code to drop a reference count" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: sysctl: Drop reference added by grab_header in proc_sys_readdir pid: fix lockdep deadlock warning due to ucount_lock libfs: Modify mount_pseudo_xattr to be clear it is not a userspace mount mnt: Protect the mountpoint hashtable with mount_lock
-rw-r--r--fs/dcache.c7
-rw-r--r--fs/libfs.c3
-rw-r--r--fs/namespace.c64
-rw-r--r--fs/proc/proc_sysctl.c3
-rw-r--r--kernel/pid_namespace.c10
5 files changed, 60 insertions, 27 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index 769903dbc19d..95d71eda8142 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1336,8 +1336,11 @@ int d_set_mounted(struct dentry *dentry)
}
spin_lock(&dentry->d_lock);
if (!d_unlinked(dentry)) {
- dentry->d_flags |= DCACHE_MOUNTED;
- ret = 0;
+ ret = -EBUSY;
+ if (!d_mountpoint(dentry)) {
+ dentry->d_flags |= DCACHE_MOUNTED;
+ ret = 0;
+ }
}
spin_unlock(&dentry->d_lock);
out:
diff --git a/fs/libfs.c b/fs/libfs.c
index e973cd51f126..28d6f35feed6 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -245,7 +245,8 @@ struct dentry *mount_pseudo_xattr(struct file_system_type *fs_type, char *name,
struct inode *root;
struct qstr d_name = QSTR_INIT(name, strlen(name));
- s = sget(fs_type, NULL, set_anon_super, MS_NOUSER, NULL);
+ s = sget_userns(fs_type, NULL, set_anon_super, MS_KERNMOUNT|MS_NOUSER,
+ &init_user_ns, NULL);
if (IS_ERR(s))
return ERR_CAST(s);
diff --git a/fs/namespace.c b/fs/namespace.c
index b5b1259e064f..487ba30bb5c6 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -742,26 +742,50 @@ static struct mountpoint *lookup_mountpoint(struct dentry *dentry)
return NULL;
}
-static struct mountpoint *new_mountpoint(struct dentry *dentry)
+static struct mountpoint *get_mountpoint(struct dentry *dentry)
{
- struct hlist_head *chain = mp_hash(dentry);
- struct mountpoint *mp;
+ struct mountpoint *mp, *new = NULL;
int ret;
- mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
- if (!mp)
+ if (d_mountpoint(dentry)) {
+mountpoint:
+ read_seqlock_excl(&mount_lock);
+ mp = lookup_mountpoint(dentry);
+ read_sequnlock_excl(&mount_lock);
+ if (mp)
+ goto done;
+ }
+
+ if (!new)
+ new = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
+ if (!new)
return ERR_PTR(-ENOMEM);
+
+ /* Exactly one processes may set d_mounted */
ret = d_set_mounted(dentry);
- if (ret) {
- kfree(mp);
- return ERR_PTR(ret);
- }
- mp->m_dentry = dentry;
- mp->m_count = 1;
- hlist_add_head(&mp->m_hash, chain);
- INIT_HLIST_HEAD(&mp->m_list);
+ /* Someone else set d_mounted? */
+ if (ret == -EBUSY)
+ goto mountpoint;
+
+ /* The dentry is not available as a mountpoint? */
+ mp = ERR_PTR(ret);
+ if (ret)
+ goto done;
+
+ /* Add the new mountpoint to the hash table */
+ read_seqlock_excl(&mount_lock);
+ new->m_dentry = dentry;
+ new->m_count = 1;
+ hlist_add_head(&new->m_hash, mp_hash(dentry));
+ INIT_HLIST_HEAD(&new->m_list);
+ read_sequnlock_excl(&mount_lock);
+
+ mp = new;
+ new = NULL;
+done:
+ kfree(new);
return mp;
}
@@ -1595,11 +1619,11 @@ void __detach_mounts(struct dentry *dentry)
struct mount *mnt;
namespace_lock();
+ lock_mount_hash();
mp = lookup_mountpoint(dentry);
if (IS_ERR_OR_NULL(mp))
goto out_unlock;
- lock_mount_hash();
event++;
while (!hlist_empty(&mp->m_list)) {
mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
@@ -1609,9 +1633,9 @@ void __detach_mounts(struct dentry *dentry)
}
else umount_tree(mnt, UMOUNT_CONNECTED);
}
- unlock_mount_hash();
put_mountpoint(mp);
out_unlock:
+ unlock_mount_hash();
namespace_unlock();
}
@@ -2038,9 +2062,7 @@ retry:
namespace_lock();
mnt = lookup_mnt(path);
if (likely(!mnt)) {
- struct mountpoint *mp = lookup_mountpoint(dentry);
- if (!mp)
- mp = new_mountpoint(dentry);
+ struct mountpoint *mp = get_mountpoint(dentry);
if (IS_ERR(mp)) {
namespace_unlock();
inode_unlock(dentry->d_inode);
@@ -2059,7 +2081,11 @@ retry:
static void unlock_mount(struct mountpoint *where)
{
struct dentry *dentry = where->m_dentry;
+
+ read_seqlock_excl(&mount_lock);
put_mountpoint(where);
+ read_sequnlock_excl(&mount_lock);
+
namespace_unlock();
inode_unlock(dentry->d_inode);
}
@@ -3135,9 +3161,9 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
touch_mnt_namespace(current->nsproxy->mnt_ns);
/* A moved mount should not expire automatically */
list_del_init(&new_mnt->mnt_expire);
+ put_mountpoint(root_mp);
unlock_mount_hash();
chroot_fs_refs(&root, &new);
- put_mountpoint(root_mp);
error = 0;
out4:
unlock_mount(old_mp);
diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 55313d994895..d4e37acd4821 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c
@@ -709,7 +709,7 @@ static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
ctl_dir = container_of(head, struct ctl_dir, header);
if (!dir_emit_dots(file, ctx))
- return 0;
+ goto out;
pos = 2;
@@ -719,6 +719,7 @@ static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
break;
}
}
+out:
sysctl_head_finish(head);
return 0;
}
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index df9e8e9e0be7..eef2ce968636 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -151,8 +151,12 @@ out:
static void delayed_free_pidns(struct rcu_head *p)
{
- kmem_cache_free(pid_ns_cachep,
- container_of(p, struct pid_namespace, rcu));
+ struct pid_namespace *ns = container_of(p, struct pid_namespace, rcu);
+
+ dec_pid_namespaces(ns->ucounts);
+ put_user_ns(ns->user_ns);
+
+ kmem_cache_free(pid_ns_cachep, ns);
}
static void destroy_pid_namespace(struct pid_namespace *ns)
@@ -162,8 +166,6 @@ static void destroy_pid_namespace(struct pid_namespace *ns)
ns_free_inum(&ns->ns);
for (i = 0; i < PIDMAP_ENTRIES; i++)
kfree(ns->pidmap[i].page);
- dec_pid_namespaces(ns->ucounts);
- put_user_ns(ns->user_ns);
call_rcu(&ns->rcu, delayed_free_pidns);
}