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author | Linus Torvalds <torvalds@linux-foundation.org> | 2017-01-15 16:09:50 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-01-15 16:09:50 -0800 |
commit | 99421c1cb27fb837e93b517036fab4500fe39de5 (patch) | |
tree | de5fc5bacb671223f389793ad643cebe520bc292 /fs | |
parent | c92816275674c1491ce228ee49aa030a5fa1be04 (diff) | |
parent | 93362fa47fe98b62e4a34ab408c4a418432e7939 (diff) | |
download | linux-99421c1cb27fb837e93b517036fab4500fe39de5.tar.gz linux-99421c1cb27fb837e93b517036fab4500fe39de5.tar.bz2 linux-99421c1cb27fb837e93b517036fab4500fe39de5.zip |
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
Diffstat (limited to 'fs')
-rw-r--r-- | fs/dcache.c | 7 | ||||
-rw-r--r-- | fs/libfs.c | 3 | ||||
-rw-r--r-- | fs/namespace.c | 64 | ||||
-rw-r--r-- | fs/proc/proc_sysctl.c | 3 |
4 files changed, 54 insertions, 23 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; } |