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LOOKUP_MOUNTPOINT: fold path_mountpointat() into path_lookupat() 

New LOOKUP flag, telling path_lookupat() to act as path_mountpointat().
IOW, traverse mounts at the final point and skip revalidation of the
location where it ends up.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2020-01-11 22:52:26 -05:00
parent cbae4d12ee
commit 161aff1d93
5 changed files with 12 additions and 90 deletions
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6
fs/autofs/dev-ioctl.c
View File

@ -186,7 +186,7 @@ static int find_autofs_mount(const char *pathname,
struct path path;
int err;
err = kern_path_mountpoint(AT_FDCWD, pathname, &path, 0);
err = kern_path(pathname, LOOKUP_MOUNTPOINT, &path);
if (err)
return err;
err = -ENOENT;
@ -519,8 +519,8 @@ static int autofs_dev_ioctl_ismountpoint(struct file *fp,
if (!fp || param->ioctlfd == -1) {
if (autofs_type_any(type))
err = kern_path_mountpoint(AT_FDCWD,
name, &path, LOOKUP_FOLLOW);
err = kern_path(name, LOOKUP_FOLLOW | LOOKUP_MOUNTPOINT,
&path);
else
err = find_autofs_mount(name, &path,
test_by_type, &type);

1
fs/internal.h
View File

@ -61,7 +61,6 @@ extern int finish_clean_context(struct fs_context *fc);
*/
extern int filename_lookup(int dfd, struct filename *name, unsigned flags,
struct path *path, struct path *root);
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 *);
long do_mknodat(int dfd, const char __user *filename, umode_t mode,

89
fs/namei.c
View File

@ -2382,6 +2382,10 @@ static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path
if (!err && nd->flags & LOOKUP_DIRECTORY)
if (!d_can_lookup(nd->path.dentry))
err = -ENOTDIR;
if (!err && unlikely(nd->flags & LOOKUP_MOUNTPOINT)) {
err = handle_lookup_down(nd);
nd->flags &= ~LOOKUP_JUMPED; // no d_weak_revalidate(), please...
}
if (!err) {
*path = nd->path;
nd->path.mnt = NULL;
@ -2410,7 +2414,8 @@ int filename_lookup(int dfd, struct filename *name, unsigned flags,
retval = path_lookupat(&nd, flags | LOOKUP_REVAL, path);
if (likely(!retval))
audit_inode(name, path->dentry, 0);
audit_inode(name, path->dentry,
flags & LOOKUP_MOUNTPOINT ? AUDIT_INODE_NOEVAL : 0);
restore_nameidata();
putname(name);
return retval;
@ -2688,88 +2693,6 @@ int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
}
EXPORT_SYMBOL(user_path_at_empty);
/**
* path_mountpoint - look up a path to be umounted
* @nd: lookup context
* @flags: lookup flags
* @path: pointer to container for result
*
* Look up the given name, but don't attempt to revalidate the last component.
* Returns 0 and "path" will be valid on success; Returns error otherwise.
*/
static int
path_mountpoint(struct nameidata *nd, unsigned flags, struct path *path)
{
const char *s = path_init(nd, flags);
int err;
while (!(err = link_path_walk(s, nd)) &&
(err = lookup_last(nd)) > 0) {
s = trailing_symlink(nd);
}
if (!err && (nd->flags & LOOKUP_RCU))
err = unlazy_walk(nd);
if (!err)
err = handle_lookup_down(nd);
if (!err) {
*path = nd->path;
nd->path.mnt = NULL;
nd->path.dentry = NULL;
}
terminate_walk(nd);
return err;
}
static int
filename_mountpoint(int dfd, struct filename *name, struct path *path,
unsigned int flags)
{
struct nameidata nd;
int error;
if (IS_ERR(name))
return PTR_ERR(name);
set_nameidata(&nd, dfd, name);
error = path_mountpoint(&nd, flags | LOOKUP_RCU, path);
if (unlikely(error == -ECHILD))
error = path_mountpoint(&nd, flags, path);
if (unlikely(error == -ESTALE))
error = path_mountpoint(&nd, flags | LOOKUP_REVAL, path);
if (likely(!error))
audit_inode(name, path->dentry, AUDIT_INODE_NOEVAL);
restore_nameidata();
putname(name);
return error;
}
/**
* user_path_mountpoint_at - lookup a path from userland in order to umount it
* @dfd: directory file descriptor
* @name: pathname from userland
* @flags: lookup flags
* @path: pointer to container to hold result
*
* A umount is a special case for path walking. We're not actually interested
* in the inode in this situation, and ESTALE errors can be a problem. We
* simply want track down the dentry and vfsmount attached at the mountpoint
* and avoid revalidating the last component.
*
* Returns 0 and populates "path" on success.
*/
int
user_path_mountpoint_at(int dfd, const char __user *name, unsigned int flags,
struct path *path)
{
return filename_mountpoint(dfd, getname(name), path, flags);
}
int
kern_path_mountpoint(int dfd, const char *name, struct path *path,
unsigned int flags)
{
return filename_mountpoint(dfd, getname_kernel(name), path, flags);
}
EXPORT_SYMBOL(kern_path_mountpoint);
int __check_sticky(struct inode *dir, struct inode *inode)
{
kuid_t fsuid = current_fsuid();

4
fs/namespace.c
View File

@ -1669,7 +1669,7 @@ int ksys_umount(char __user *name, int flags)
struct path path;
struct mount *mnt;
int retval;
int lookup_flags = 0;
int lookup_flags = LOOKUP_MOUNTPOINT;
if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
return -EINVAL;
@ -1680,7 +1680,7 @@ int ksys_umount(char __user *name, int flags)
if (!(flags & UMOUNT_NOFOLLOW))
lookup_flags |= LOOKUP_FOLLOW;
retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path);
retval = user_path_at(AT_FDCWD, name, lookup_flags, &path);
if (retval)
goto out;
mnt = real_mount(path.mnt);

2
include/linux/namei.h
View File

@ -23,6 +23,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND};
#define LOOKUP_AUTOMOUNT 0x0004 /* force terminal automount */
#define LOOKUP_EMPTY 0x4000 /* accept empty path [user_... only] */
#define LOOKUP_DOWN 0x8000 /* follow mounts in the starting point */
#define LOOKUP_MOUNTPOINT 0x0080 /* follow mounts in the end */
#define LOOKUP_REVAL 0x0020 /* tell ->d_revalidate() to trust no cache */
#define LOOKUP_RCU 0x0040 /* RCU pathwalk mode; semi-internal */
@ -64,7 +65,6 @@ extern struct dentry *kern_path_create(int, const char *, struct path *, unsigne
extern struct dentry *user_path_create(int, const char __user *, struct path *, unsigned int);
extern void done_path_create(struct path *, struct dentry *);
extern struct dentry *kern_path_locked(const char *, struct path *);
extern int kern_path_mountpoint(int, const char *, struct path *, unsigned int);
extern struct dentry *try_lookup_one_len(const char *, struct dentry *, int);
extern struct dentry *lookup_one_len(const char *, struct dentry *, int);