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authorLinus Torvalds <torvalds@linux-foundation.org>2017-05-12 11:39:59 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-05-12 11:39:59 -0700
commit050453295f808dd683b9a88f58a1b29540097394 (patch)
tree1d43b39b72779d9133de345a96a6ea92cf96582c
parente0c4a5fc750e22c6f8d5c1ab7cc18592b88852ab (diff)
parent4f757f3cbf54edef7b75c68d6d6d2f1a0ca08d2e (diff)
downloadlinux-stericsson-050453295f808dd683b9a88f58a1b29540097394.tar.gz
Merge branch 'work.sane_pwd' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull misc vfs updates from Al Viro: "Making sure that something like a referral point won't end up as pwd or root. The main part is the last commit (fixing mntns_install()); that one fixes a hard-to-hit race. The fchdir() commit is making fchdir(2) a bit more robust - it should be impossible to get opened files (even O_PATH ones) for referral points in the first place, so the existing checks are OK, but checking the same thing as in chdir(2) is just as cheap. The path_init() commit removes a redundant check that shouldn't have been there in the first place" * 'work.sane_pwd' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: make sure that mntns_install() doesn't end up with referral for root path_init(): don't bother with checking MAY_EXEC for LOOKUP_ROOT make sure that fchdir() won't accept referral points, etc.
-rw-r--r--fs/namei.c48
-rw-r--r--fs/namespace.c18
-rw-r--r--fs/open.c9
-rw-r--r--include/linux/namei.h1
4 files changed, 55 insertions, 21 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 7286f87ce863..6571a5f5112e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2142,7 +2142,6 @@ OK:
static const char *path_init(struct nameidata *nd, unsigned flags)
{
- int retval = 0;
const char *s = nd->name->name;
if (!*s)
@@ -2154,13 +2153,8 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
if (flags & LOOKUP_ROOT) {
struct dentry *root = nd->root.dentry;
struct inode *inode = root->d_inode;
- if (*s) {
- if (!d_can_lookup(root))
- return ERR_PTR(-ENOTDIR);
- retval = inode_permission(inode, MAY_EXEC);
- if (retval)
- return ERR_PTR(retval);
- }
+ if (*s && unlikely(!d_can_lookup(root)))
+ return ERR_PTR(-ENOTDIR);
nd->path = nd->root;
nd->inode = inode;
if (flags & LOOKUP_RCU) {
@@ -2258,6 +2252,35 @@ static inline int lookup_last(struct nameidata *nd)
return walk_component(nd, 0);
}
+static int handle_lookup_down(struct nameidata *nd)
+{
+ struct path path = nd->path;
+ struct inode *inode = nd->inode;
+ unsigned seq = nd->seq;
+ int err;
+
+ if (nd->flags & LOOKUP_RCU) {
+ /*
+ * don't bother with unlazy_walk on failure - we are
+ * at the very beginning of walk, so we lose nothing
+ * if we simply redo everything in non-RCU mode
+ */
+ if (unlikely(!__follow_mount_rcu(nd, &path, &inode, &seq)))
+ return -ECHILD;
+ } else {
+ dget(path.dentry);
+ err = follow_managed(&path, nd);
+ if (unlikely(err < 0))
+ return err;
+ inode = d_backing_inode(path.dentry);
+ seq = 0;
+ }
+ path_to_nameidata(&path, nd);
+ nd->inode = inode;
+ nd->seq = seq;
+ return 0;
+}
+
/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path)
{
@@ -2266,6 +2289,15 @@ static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path
if (IS_ERR(s))
return PTR_ERR(s);
+
+ if (unlikely(flags & LOOKUP_DOWN)) {
+ err = handle_lookup_down(nd);
+ if (unlikely(err < 0)) {
+ terminate_walk(nd);
+ return err;
+ }
+ }
+
while (!(err = link_path_walk(s, nd))
&& ((err = lookup_last(nd)) > 0)) {
s = trailing_symlink(nd);
diff --git a/fs/namespace.c b/fs/namespace.c
index b3b115bd4e1e..8bd3e4d448b9 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3462,8 +3462,9 @@ static void mntns_put(struct ns_common *ns)
static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)
{
struct fs_struct *fs = current->fs;
- struct mnt_namespace *mnt_ns = to_mnt_ns(ns);
+ struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns;
struct path root;
+ int err;
if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
!ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
@@ -3474,15 +3475,18 @@ static int mntns_install(struct nsproxy *nsproxy, struct ns_common *ns)
return -EINVAL;
get_mnt_ns(mnt_ns);
- put_mnt_ns(nsproxy->mnt_ns);
+ old_mnt_ns = nsproxy->mnt_ns;
nsproxy->mnt_ns = mnt_ns;
/* Find the root */
- root.mnt = &mnt_ns->root->mnt;
- root.dentry = mnt_ns->root->mnt.mnt_root;
- path_get(&root);
- while(d_mountpoint(root.dentry) && follow_down_one(&root))
- ;
+ err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt,
+ "/", LOOKUP_DOWN, &root);
+ if (err) {
+ /* revert to old namespace */
+ nsproxy->mnt_ns = old_mnt_ns;
+ put_mnt_ns(mnt_ns);
+ return err;
+ }
/* Update the pwd and root */
set_fs_pwd(fs, &root);
diff --git a/fs/open.c b/fs/open.c
index 6d2d2b33ac54..cd0c5be8d012 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -460,20 +460,17 @@ out:
SYSCALL_DEFINE1(fchdir, unsigned int, fd)
{
struct fd f = fdget_raw(fd);
- struct inode *inode;
- int error = -EBADF;
+ int error;
error = -EBADF;
if (!f.file)
goto out;
- inode = file_inode(f.file);
-
error = -ENOTDIR;
- if (!S_ISDIR(inode->i_mode))
+ if (!d_can_lookup(f.file->f_path.dentry))
goto out_putf;
- error = inode_permission(inode, MAY_EXEC | MAY_CHDIR);
+ error = inode_permission(file_inode(f.file), MAY_EXEC | MAY_CHDIR);
if (!error)
set_fs_pwd(current->fs, &f.file->f_path);
out_putf:
diff --git a/include/linux/namei.h b/include/linux/namei.h
index f29abda31e6d..8b4794e83196 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -44,6 +44,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
#define LOOKUP_JUMPED 0x1000
#define LOOKUP_ROOT 0x2000
#define LOOKUP_EMPTY 0x4000
+#define LOOKUP_DOWN 0x8000
extern int path_pts(struct path *path);