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Merge branch 'work.namei' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Browse Source 
Pull vfs name lookup updates from Al Viro:
 "Small namei.c patch series, mostly to simplify the rules for nameidata
  state. It's actually from the previous cycle - but I didn't post it
  for review in time...

  Changes visible outside of fs/namei.c: file_open_root() calling
  conventions change, some freed bits in LOOKUP_... space"

* 'work.namei' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  namei: make sure nd->depth is always valid
  teach set_nameidata() to handle setting the root as well
  take LOOKUP_{ROOT,ROOT_GRABBED,JUMPED} out of LOOKUP_... space
  switch file_open_root() to struct path
This commit is contained in:
Linus Torvalds 2021-07-03 11:41:14 -07:00
commit 58ec9059b3
14 changed files with 74 additions and 56 deletions
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6
Documentation/filesystems/path-lookup.rst
View File

@ -1297,18 +1297,18 @@ to lookup: RCU-walk, REF-walk, and REF-walk with forced revalidation.
yet. This is primarily used to tell the audit subsystem the full
context of a particular access being audited.
``LOOKUP_ROOT`` indicates that the ``root`` field in the ``nameidata`` was
``ND_ROOT_PRESET`` indicates that the ``root`` field in the ``nameidata`` was
provided by the caller, so it shouldn't be released when it is no
longer needed.
``LOOKUP_JUMPED`` means that the current dentry was chosen not because
``ND_JUMPED`` means that the current dentry was chosen not because
it had the right name but for some other reason. This happens when
following "``..``", following a symlink to ``/``, crossing a mount point
or accessing a "``/proc/$PID/fd/$FD``" symlink (also known as a "magic
link"). In this case the filesystem has not been asked to revalidate the
name (with ``d_revalidate()``). In such cases the inode may still need
to be revalidated, so ``d_op->d_weak_revalidate()`` is called if
``LOOKUP_JUMPED`` is set when the look completes - which may be at the
``ND_JUMPED`` is set when the look completes - which may be at the
final component or, when creating, unlinking, or renaming, at the penultimate component.
Resolution-restriction flags

9
Documentation/filesystems/porting.rst
View File

@ -899,3 +899,12 @@ iov_iter_copy_from_user_atomic() is gone; use copy_page_from_iter_atomic().
The difference is copy_page_from_iter_atomic() advances the iterator and
you don't need iov_iter_advance() after it. However, if you decide to use
only a part of obtained data, you should do iov_iter_revert().
---
**mandatory**
Calling conventions for file_open_root() changed; now it takes struct path *
instead of passing mount and dentry separately. For callers that used to
pass <mnt, mnt->mnt_root> pair (i.e. the root of given mount), a new helper
is provided - file_open_root_mnt(). In-tree users adjusted.

2
arch/um/drivers/mconsole_kern.c
View File

@ -141,7 +141,7 @@ void mconsole_proc(struct mc_request *req)
mconsole_reply(req, "Proc not available", 1, 0);
goto out;
}
file = file_open_root(mnt->mnt_root, mnt, ptr, O_RDONLY, 0);
file = file_open_root_mnt(mnt, ptr, O_RDONLY, 0);
if (IS_ERR(file)) {
mconsole_reply(req, "Failed to open file", 1, 0);
printk(KERN_ERR "open /proc/%s: %ld\n", ptr, PTR_ERR(file));

4
fs/coredump.c
View File

@ -755,8 +755,8 @@ void do_coredump(const kernel_siginfo_t *siginfo)
task_lock(&init_task);
get_fs_root(init_task.fs, &root);
task_unlock(&init_task);
cprm.file = file_open_root(root.dentry, root.mnt,
cn.corename, open_flags, 0600);
cprm.file = file_open_root(&root, cn.corename,
open_flags, 0600);
path_put(&root);
} else {
cprm.file = filp_open(cn.corename, open_flags, 0600);

2
fs/fhandle.c
View File

@ -229,7 +229,7 @@ static long do_handle_open(int mountdirfd, struct file_handle __user *ufh,
path_put(&path);
return fd;
}
file = file_open_root(path.dentry, path.mnt, "", open_flag, 0);
file = file_open_root(&path, "", open_flag, 0);
if (IS_ERR(file)) {
put_unused_fd(fd);
retval = PTR_ERR(file);

2
fs/internal.h
View File

@ -129,7 +129,7 @@ struct open_flags {
};
extern struct file *do_filp_open(int dfd, struct filename *pathname,
const struct open_flags *op);
extern struct file *do_file_open_root(struct dentry *, struct vfsmount *,
extern struct file *do_file_open_root(const struct path *,
const char *, const struct open_flags *);
extern struct open_how build_open_how(int flags, umode_t mode);
extern int build_open_flags(const struct open_how *how, struct open_flags *op);

2
fs/kernel_read_file.c
View File

@ -160,7 +160,7 @@ int kernel_read_file_from_path_initns(const char *path, loff_t offset,
get_fs_root(init_task.fs, &root);
task_unlock(&init_task);
file = file_open_root(root.dentry, root.mnt, path, O_RDONLY, 0);
file = file_open_root(&root, path, O_RDONLY, 0);
path_put(&root);
if (IS_ERR(file))
return PTR_ERR(file);

80
fs/namei.c
View File

@ -554,7 +554,7 @@ struct nameidata {
struct qstr last;
struct path root;
struct inode *inode; /* path.dentry.d_inode */
unsigned int flags;
unsigned int flags, state;
unsigned seq, m_seq, r_seq;
int last_type;
unsigned depth;
@ -573,10 +573,15 @@ struct nameidata {
umode_t dir_mode;
} __randomize_layout;
static void set_nameidata(struct nameidata *p, int dfd, struct filename *name)
#define ND_ROOT_PRESET 1
#define ND_ROOT_GRABBED 2
#define ND_JUMPED 4
static void __set_nameidata(struct nameidata *p, int dfd, struct filename *name)
{
struct nameidata *old = current->nameidata;
p->stack = p->internal;
p->depth = 0;
p->dfd = dfd;
p->name = name;
p->path.mnt = NULL;
@ -586,6 +591,17 @@ static void set_nameidata(struct nameidata *p, int dfd, struct filename *name)
current->nameidata = p;
}
static inline void set_nameidata(struct nameidata *p, int dfd, struct filename *name,
const struct path *root)
{
__set_nameidata(p, dfd, name);
p->state = 0;
if (unlikely(root)) {
p->state = ND_ROOT_PRESET;
p->root = *root;
}
}
static void restore_nameidata(void)
{
struct nameidata *now = current->nameidata, *old = now->saved;
@ -645,9 +661,9 @@ static void terminate_walk(struct nameidata *nd)
path_put(&nd->path);
for (i = 0; i < nd->depth; i++)
path_put(&nd->stack[i].link);
if (nd->flags & LOOKUP_ROOT_GRABBED) {
if (nd->state & ND_ROOT_GRABBED) {
path_put(&nd->root);
nd->flags &= ~LOOKUP_ROOT_GRABBED;
nd->state &= ~ND_ROOT_GRABBED;
}
} else {
nd->flags &= ~LOOKUP_RCU;
@ -710,9 +726,9 @@ static bool legitimize_root(struct nameidata *nd)
if (!nd->root.mnt && (nd->flags & LOOKUP_IS_SCOPED))
return false;
/* Nothing to do if nd->root is zero or is managed by the VFS user. */
if (!nd->root.mnt || (nd->flags & LOOKUP_ROOT))
if (!nd->root.mnt || (nd->state & ND_ROOT_PRESET))
return true;
nd->flags |= LOOKUP_ROOT_GRABBED;
nd->state |= ND_ROOT_GRABBED;
return legitimize_path(nd, &nd->root, nd->root_seq);
}
@ -849,8 +865,9 @@ static int complete_walk(struct nameidata *nd)
* We don't want to zero nd->root for scoped-lookups or
* externally-managed nd->root.
*/
if (!(nd->flags & (LOOKUP_ROOT | LOOKUP_IS_SCOPED)))
nd->root.mnt = NULL;
if (!(nd->state & ND_ROOT_PRESET))
if (!(nd->flags & LOOKUP_IS_SCOPED))
nd->root.mnt = NULL;
nd->flags &= ~LOOKUP_CACHED;
if (!try_to_unlazy(nd))
return -ECHILD;
@ -877,7 +894,7 @@ static int complete_walk(struct nameidata *nd)
return -EXDEV;
}
if (likely(!(nd->flags & LOOKUP_JUMPED)))
if (likely(!(nd->state & ND_JUMPED)))
return 0;
if (likely(!(dentry->d_flags & DCACHE_OP_WEAK_REVALIDATE)))
@ -915,7 +932,7 @@ static int set_root(struct nameidata *nd)
} while (read_seqcount_retry(&fs->seq, seq));
} else {
get_fs_root(fs, &nd->root);
nd->flags |= LOOKUP_ROOT_GRABBED;
nd->state |= ND_ROOT_GRABBED;
}
return 0;
}
@ -948,7 +965,7 @@ static int nd_jump_root(struct nameidata *nd)
path_get(&nd->path);
nd->inode = nd->path.dentry->d_inode;
}
nd->flags |= LOOKUP_JUMPED;
nd->state |= ND_JUMPED;
return 0;
}
@ -976,7 +993,7 @@ int nd_jump_link(struct path *path)
path_put(&nd->path);
nd->path = *path;
nd->inode = nd->path.dentry->d_inode;
nd->flags |= LOOKUP_JUMPED;
nd->state |= ND_JUMPED;
return 0;
err:
@ -1423,7 +1440,7 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
if (mounted) {
path->mnt = &mounted->mnt;
dentry = path->dentry = mounted->mnt.mnt_root;
nd->flags |= LOOKUP_JUMPED;
nd->state |= ND_JUMPED;
*seqp = read_seqcount_begin(&dentry->d_seq);
*inode = dentry->d_inode;
/*
@ -1468,7 +1485,7 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,
if (unlikely(nd->flags & LOOKUP_NO_XDEV))
ret = -EXDEV;
else
nd->flags |= LOOKUP_JUMPED;
nd->state |= ND_JUMPED;
}
if (unlikely(ret)) {
dput(path->dentry);
@ -2219,7 +2236,7 @@ static int link_path_walk(const char *name, struct nameidata *nd)
case 2:
if (name[1] == '.') {
type = LAST_DOTDOT;
nd->flags |= LOOKUP_JUMPED;
nd->state |= ND_JUMPED;
}
break;
case 1:
@ -2227,7 +2244,7 @@ static int link_path_walk(const char *name, struct nameidata *nd)
}
if (likely(type == LAST_NORM)) {
struct dentry *parent = nd->path.dentry;
nd->flags &= ~LOOKUP_JUMPED;
nd->state &= ~ND_JUMPED;
if (unlikely(parent->d_flags & DCACHE_OP_HASH)) {
struct qstr this = { { .hash_len = hash_len }, .name = name };
err = parent->d_op->d_hash(parent, &this);
@ -2301,14 +2318,14 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
if (flags & LOOKUP_RCU)
rcu_read_lock();
nd->flags = flags | LOOKUP_JUMPED;
nd->depth = 0;
nd->flags = flags;
nd->state |= ND_JUMPED;
nd->m_seq = __read_seqcount_begin(&mount_lock.seqcount);
nd->r_seq = __read_seqcount_begin(&rename_lock.seqcount);
smp_rmb();
if (flags & LOOKUP_ROOT) {
if (nd->state & ND_ROOT_PRESET) {
struct dentry *root = nd->root.dentry;
struct inode *inode = root->d_inode;
if (*s && unlikely(!d_can_lookup(root)))
@ -2383,7 +2400,7 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
nd->root_seq = nd->seq;
} else {
path_get(&nd->root);
nd->flags |= LOOKUP_ROOT_GRABBED;
nd->state |= ND_ROOT_GRABBED;
}
}
return s;
@ -2422,7 +2439,7 @@ static int path_lookupat(struct nameidata *nd, unsigned flags, struct path *path
;
if (!err && unlikely(nd->flags & LOOKUP_MOUNTPOINT)) {
err = handle_lookup_down(nd);
nd->flags &= ~LOOKUP_JUMPED; // no d_weak_revalidate(), please...
nd->state &= ~ND_JUMPED; // no d_weak_revalidate(), please...
}
if (!err)
err = complete_walk(nd);
@ -2446,11 +2463,7 @@ int filename_lookup(int dfd, struct filename *name, unsigned flags,
struct nameidata nd;
if (IS_ERR(name))
return PTR_ERR(name);
if (unlikely(root)) {
nd.root = *root;
flags |= LOOKUP_ROOT;
}
set_nameidata(&nd, dfd, name);
set_nameidata(&nd, dfd, name, root);
retval = path_lookupat(&nd, flags | LOOKUP_RCU, path);
if (unlikely(retval == -ECHILD))
retval = path_lookupat(&nd, flags, path);
@ -2491,7 +2504,7 @@ static struct filename *filename_parentat(int dfd, struct filename *name,
if (IS_ERR(name))
return name;
set_nameidata(&nd, dfd, name);
set_nameidata(&nd, dfd, name, NULL);
retval = path_parentat(&nd, flags | LOOKUP_RCU, parent);
if (unlikely(retval == -ECHILD))
retval = path_parentat(&nd, flags, parent);
@ -3517,7 +3530,7 @@ struct file *do_filp_open(int dfd, struct filename *pathname,
int flags = op->lookup_flags;
struct file *filp;
set_nameidata(&nd, dfd, pathname);
set_nameidata(&nd, dfd, pathname, NULL);
filp = path_openat(&nd, op, flags | LOOKUP_RCU);
if (unlikely(filp == ERR_PTR(-ECHILD)))
filp = path_openat(&nd, op, flags);
@ -3527,25 +3540,22 @@ struct file *do_filp_open(int dfd, struct filename *pathname,
return filp;
}
struct file *do_file_open_root(struct dentry *dentry, struct vfsmount *mnt,
struct file *do_file_open_root(const struct path *root,
const char *name, const struct open_flags *op)
{
struct nameidata nd;
struct file *file;
struct filename *filename;
int flags = op->lookup_flags | LOOKUP_ROOT;
int flags = op->lookup_flags;
nd.root.mnt = mnt;
nd.root.dentry = dentry;
if (d_is_symlink(dentry) && op->intent & LOOKUP_OPEN)
if (d_is_symlink(root->dentry) && op->intent & LOOKUP_OPEN)
return ERR_PTR(-ELOOP);
filename = getname_kernel(name);
if (IS_ERR(filename))
return ERR_CAST(filename);
set_nameidata(&nd, -1, filename);
set_nameidata(&nd, -1, filename, root);
file = path_openat(&nd, op, flags | LOOKUP_RCU);
if (unlikely(file == ERR_PTR(-ECHILD)))
file = path_openat(&nd, op, flags);

4
fs/nfs/nfstrace.h
View File

@ -280,8 +280,6 @@ TRACE_DEFINE_ENUM(LOOKUP_OPEN);
TRACE_DEFINE_ENUM(LOOKUP_CREATE);
TRACE_DEFINE_ENUM(LOOKUP_EXCL);
TRACE_DEFINE_ENUM(LOOKUP_RENAME_TARGET);
TRACE_DEFINE_ENUM(LOOKUP_JUMPED);
TRACE_DEFINE_ENUM(LOOKUP_ROOT);
TRACE_DEFINE_ENUM(LOOKUP_EMPTY);
TRACE_DEFINE_ENUM(LOOKUP_DOWN);
@ -297,8 +295,6 @@ TRACE_DEFINE_ENUM(LOOKUP_DOWN);
{ LOOKUP_CREATE, "CREATE" }, \
{ LOOKUP_EXCL, "EXCL" }, \
{ LOOKUP_RENAME_TARGET, "RENAME_TARGET" }, \
{ LOOKUP_JUMPED, "JUMPED" }, \
{ LOOKUP_ROOT, "ROOT" }, \
{ LOOKUP_EMPTY, "EMPTY" }, \
{ LOOKUP_DOWN, "DOWN" })

4
fs/open.c
View File

@ -1173,7 +1173,7 @@ struct file *filp_open(const char *filename, int flags, umode_t mode)
}
EXPORT_SYMBOL(filp_open);
struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
struct file *file_open_root(const struct path *root,
const char *filename, int flags, umode_t mode)
{
struct open_flags op;
@ -1181,7 +1181,7 @@ struct file *file_open_root(struct dentry *dentry, struct vfsmount *mnt,
int err = build_open_flags(&how, &op);
if (err)
return ERR_PTR(err);
return do_file_open_root(dentry, mnt, filename, &op);
return do_file_open_root(root, filename, &op);
}
EXPORT_SYMBOL(file_open_root);

2
fs/proc/proc_sysctl.c
View File

@ -1807,7 +1807,7 @@ static int process_sysctl_arg(char *param, char *val,
panic("%s: Failed to allocate path for %s\n", __func__, param);
strreplace(path, '.', '/');
file = file_open_root((*proc_mnt)->mnt_root, *proc_mnt, path, O_WRONLY, 0);
file = file_open_root_mnt(*proc_mnt, path, O_WRONLY, 0);
if (IS_ERR(file)) {
err = PTR_ERR(file);
if (err == -ENOENT)

8
include/linux/fs.h
View File

@ -2768,8 +2768,14 @@ extern long do_sys_open(int dfd, const char __user *filename, int flags,
umode_t mode);
extern struct file *file_open_name(struct filename *, int, umode_t);
extern struct file *filp_open(const char *, int, umode_t);
extern struct file *file_open_root(struct dentry *, struct vfsmount *,
extern struct file *file_open_root(const struct path *,
const char *, int, umode_t);
static inline struct file *file_open_root_mnt(struct vfsmount *mnt,
const char *name, int flags, umode_t mode)
{
return file_open_root(&(struct path){.mnt = mnt, .dentry = mnt->mnt_root},
name, flags, mode);
}
extern struct file * dentry_open(const struct path *, int, const struct cred *);
extern struct file * open_with_fake_path(const struct path *, int,
struct inode*, const struct cred *);

3
include/linux/namei.h
View File

@ -36,9 +36,6 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT};
/* internal use only */
#define LOOKUP_PARENT 0x0010
#define LOOKUP_JUMPED 0x1000
#define LOOKUP_ROOT 0x2000
#define LOOKUP_ROOT_GRABBED 0x0008
/* Scoping flags for lookup. */
#define LOOKUP_NO_SYMLINKS 0x010000 /* No symlink crossing. */

2
kernel/usermode_driver.c
View File

@ -26,7 +26,7 @@ static struct vfsmount *blob_to_mnt(const void *data, size_t len, const char *na
if (IS_ERR(mnt))
return mnt;
file = file_open_root(mnt->mnt_root, mnt, name, O_CREAT | O_WRONLY, 0700);
file = file_open_root_mnt(mnt, name, O_CREAT | O_WRONLY, 0700);
if (IS_ERR(file)) {
mntput(mnt);
return ERR_CAST(file);