- Add a dentry flag DCACHE_MOUNT_VIOLATED to mark loopback mounts that
have had a dentry moved into a directory that does not descend from
the mount root dentry.
- In mnt_put_root clear DCACHE_MOUNT_VIOLATED.
- Add a function path_connected to verify a path.dentry is reachable from
path.mnt.mnt_root. AKA rename did not do something nasty to the bind mount.
- Disable ".." when a path is not connected during lookup.
(Maybe we want to stop ".." at this path instead?)
Following .. is not disabled after a transition to /
and is never disabled when / is the directory we start
with. Because we already limit .. no higher than /
- In prepend_path and it's callers in the d_path family
for a path that is not connected don't attempt to find
parent directories.
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
---
fs/dcache.c | 3 +++
fs/internal.h | 1 +
fs/namei.c | 30 ++++++++++++++++++++++++++++++
fs/namespace.c | 2 +-
include/linux/dcache.h | 6 ++++++
include/linux/namei.h | 2 ++
6 files changed, 43 insertions(+), 1 deletion(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index c71e3732e53b..e07eb03f6de6 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2871,6 +2871,9 @@ static int prepend_path(const struct path *path,
char *bptr;
int blen;
+ if (!path_connected(path))
+ root = path;
+
rcu_read_lock();
restart_mnt:
read_seqbegin_or_lock(&mount_lock, &m_seq);
diff --git a/fs/internal.h b/fs/internal.h
index 01dce1d1476b..046767f0042e 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -51,6 +51,7 @@ extern void __init chrdev_init(void);
extern int user_path_mountpoint_at(int, const char __user *, unsigned int, struct path *);
extern int vfs_path_lookup(struct dentry *, struct vfsmount *,
const char *, unsigned int, struct path *);
+extern bool path_connected(const struct path *);
/*
* namespace.c
diff --git a/fs/namei.c b/fs/namei.c
index c83145af4bfc..83cdcdf36eed 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -493,6 +493,22 @@ void path_put(const struct path *path)
}
EXPORT_SYMBOL(path_put);
+/**
+ * path_connected - Verify that a path->dentry is below path->mnt->mnt.mnt_root
+ * @path: path to verify
+ *
+ * Rename can sometimes move a file or directory outside of bind mount
+ * don't honor paths where this has happened.
+ */
+bool path_connected(const struct path *path)
+{
+ struct dentry *root = path->mnt->mnt_root;
+ if (!d_mount_violated(root))
+ return true;
+
+ return is_subdir(path->dentry, root);
+}
+
struct nameidata {
struct path path;
struct qstr last;
@@ -712,6 +728,7 @@ void nd_jump_link(struct nameidata *nd, struct path *path)
nd->path = *path;
nd->inode = nd->path.dentry->d_inode;
nd->flags |= LOOKUP_JUMPED;
+ nd->flags &= ~LOOKUP_NODOTDOT;
}
void nd_set_link(struct nameidata *nd, char *path)
@@ -897,6 +914,7 @@ follow_link(struct path *link, struct nameidata *nd, void **p)
nd->path = nd->root;
path_get(&nd->root);
nd->flags |= LOOKUP_JUMPED;
+ nd->flags &= ~LOOKUP_NODOTDOT;
}
nd->inode = nd->path.dentry->d_inode;
error = link_path_walk(s, nd);
@@ -1161,6 +1179,7 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
path->mnt = &mounted->mnt;
path->dentry = mounted->mnt.mnt_root;
nd->flags |= LOOKUP_JUMPED;
+ nd->flags &= ~LOOKUP_NODOTDOT;
nd->seq = read_seqcount_begin(&path->dentry->d_seq);
/*
* Update the inode too. We don't need to re-check the
@@ -1176,6 +1195,10 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
static int follow_dotdot_rcu(struct nameidata *nd)
{
struct inode *inode = nd->inode;
+
+ if (nd->flags & LOOKUP_NODOTDOT)
+ return 0;
+
if (!nd->root.mnt)
set_root_rcu(nd);
@@ -1293,6 +1316,9 @@ static void follow_mount(struct path *path)
static void follow_dotdot(struct nameidata *nd)
{
+ if (nd->flags & LOOKUP_NODOTDOT)
+ return;
+
if (!nd->root.mnt)
set_root(nd);
@@ -1909,6 +1935,8 @@ static int path_init(int dfd, const char *name, unsigned int flags,
} else {
get_fs_pwd(current->fs, &nd->path);
}
+ if (unlikely(!path_connected(&nd->path)))
+ nd->flags |= LOOKUP_NODOTDOT;
} else {
/* Caller must check execute permissions on the starting path component */
struct fd f = fdget_raw(dfd);
@@ -1936,6 +1964,8 @@ static int path_init(int dfd, const char *name, unsigned int flags,
path_get(&nd->path);
fdput(f);
}
+ if (unlikely(!path_connected(&nd->path)))
+ nd->flags |= LOOKUP_NODOTDOT;
}
nd->inode = nd->path.dentry->d_inode;
diff --git a/fs/namespace.c b/fs/namespace.c
index 0b517f1e898a..75abc9fcaafa 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -850,7 +850,7 @@ static void mnt_put_root(struct mount *mnt)
if (!--mr->r_count) {
hlist_del(&mr->r_hash);
spin_lock(&root->d_lock);
- root->d_flags &= ~DCACHE_MOUNTROOT;
+ root->d_flags &= ~(DCACHE_MOUNTROOT | DCACHE_MOUNT_VIOLATED);
spin_unlock(&root->d_lock);
kfree(mr);
}
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 01cd930bf9d8..18e36d974168 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -227,6 +227,7 @@ struct dentry_operations {
#define DCACHE_FALLTHRU 0x01000000 /* Fall through to lower layer */
#define DCACHE_MOUNTROOT 0x02000000 /* Root of a vfsmount */
+#define DCACHE_MOUNT_VIOLATED 0x04000000 /* Vfsmount with dentries moved out */
extern seqlock_t rename_lock;
@@ -408,6 +409,11 @@ static inline bool d_mountroot(const struct dentry *dentry)
return dentry->d_flags & DCACHE_MOUNTROOT;
}
+static inline bool d_mount_violated(const struct dentry *dentry)
+{
+ return dentry->d_flags & DCACHE_MOUNT_VIOLATED;
+}
+
/*
* Directory cache entry type accessor functions.
*/
diff --git a/include/linux/namei.h b/include/linux/namei.h
index c8990779f0c3..55c8aaec7b03 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -45,6 +45,8 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
#define LOOKUP_ROOT 0x2000
#define LOOKUP_EMPTY 0x4000
+#define LOOKUP_NODOTDOT 0x10000
+
extern int user_path_at(int, const char __user *, unsigned, struct path *);
extern int user_path_at_empty(int, const char __user *, unsigned, struct path *, int *empty);
--
2.2.1
--
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