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sanitize path_walk() mess
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New helper: path_lookupat().  Basically, what do_path_lookup() boils to
modulo -ECHILD/-ESTALE handler.  path_walk* family is gone; vfs_path_lookup()
is using link_path_walk() directly, do_path_lookup() and do_filp_open()
are using path_lookupat().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Al Viro committed Mar 14, 2011
1 parent 52094c8 commit ee0827c
Showing 1 changed file with 56 additions and 92 deletions.
148 changes: 56 additions & 92 deletions fs/namei.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1520,59 +1520,6 @@ static int link_path_walk(const char *name, struct nameidata *nd)
return err;
}

static inline int path_walk_rcu(const char *name, struct nameidata *nd)
{
current->total_link_count = 0;

return link_path_walk(name, nd);
}

static inline int path_walk_simple(const char *name, struct nameidata *nd)
{
current->total_link_count = 0;

return link_path_walk(name, nd);
}

static int path_walk(const char *name, struct nameidata *nd)
{
struct path save = nd->path;
int result;

current->total_link_count = 0;

/* make sure the stuff we saved doesn't go away */
path_get(&save);

result = link_path_walk(name, nd);
if (result == -ESTALE) {
/* nd->path had been dropped */
current->total_link_count = 0;
nd->path = save;
nd->inode = save.dentry->d_inode;
path_get(&nd->path);
nd->flags |= LOOKUP_REVAL;
result = link_path_walk(name, nd);
}

path_put(&save);

return result;
}

static void path_finish_rcu(struct nameidata *nd)
{
if (nd->flags & LOOKUP_RCU) {
/* RCU dangling. Cancel it. */
nd->flags &= ~LOOKUP_RCU;
nd->root.mnt = NULL;
rcu_read_unlock();
br_read_unlock(vfsmount_lock);
}
if (nd->file)
fput(nd->file);
}

static int path_init_rcu(int dfd, const char *name, unsigned int flags, struct nameidata *nd)
{
int retval = 0;
Expand Down Expand Up @@ -1697,7 +1644,7 @@ static int path_init(int dfd, const char *name, unsigned int flags, struct namei
}

/* Returns 0 and nd will be valid on success; Retuns error, otherwise. */
static int do_path_lookup(int dfd, const char *name,
static int path_lookupat(int dfd, const char *name,
unsigned int flags, struct nameidata *nd)
{
int retval;
Expand All @@ -1716,37 +1663,52 @@ static int do_path_lookup(int dfd, const char *name,
* be handled by restarting a traditional ref-walk (which will always
* be able to complete).
*/
retval = path_init_rcu(dfd, name, flags, nd);
if (flags & LOOKUP_RCU)
retval = path_init_rcu(dfd, name, flags, nd);
else
retval = path_init(dfd, name, flags, nd);

if (unlikely(retval))
return retval;
retval = path_walk_rcu(name, nd);
path_finish_rcu(nd);

current->total_link_count = 0;
retval = link_path_walk(name, nd);

if (nd->flags & LOOKUP_RCU) {
/* RCU dangling. Cancel it. */
nd->flags &= ~LOOKUP_RCU;
nd->root.mnt = NULL;
rcu_read_unlock();
br_read_unlock(vfsmount_lock);
}

if (nd->file) {
fput(nd->file);
nd->file = NULL;
}

if (nd->root.mnt) {
path_put(&nd->root);
nd->root.mnt = NULL;
}
return retval;
}

if (unlikely(retval == -ECHILD || retval == -ESTALE)) {
/* slower, locked walk */
if (retval == -ESTALE)
flags |= LOOKUP_REVAL;
retval = path_init(dfd, name, flags, nd);
if (unlikely(retval))
return retval;
retval = path_walk(name, nd);
if (nd->root.mnt) {
path_put(&nd->root);
nd->root.mnt = NULL;
}
}
static int do_path_lookup(int dfd, const char *name,
unsigned int flags, struct nameidata *nd)
{
int retval = path_lookupat(dfd, name, flags | LOOKUP_RCU, nd);
if (unlikely(retval == -ECHILD))
retval = path_lookupat(dfd, name, flags, nd);
if (unlikely(retval == -ESTALE))
retval = path_lookupat(dfd, name, flags | LOOKUP_REVAL, nd);

if (likely(!retval)) {
if (unlikely(!audit_dummy_context())) {
if (nd->path.dentry && nd->inode)
audit_inode(name, nd->path.dentry);
}
}

return retval;
}

Expand Down Expand Up @@ -1776,7 +1738,7 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
const char *name, unsigned int flags,
struct nameidata *nd)
{
int retval;
int result;

/* same as do_path_lookup */
nd->last_type = LAST_ROOT;
Expand All @@ -1790,15 +1752,27 @@ int vfs_path_lookup(struct dentry *dentry, struct vfsmount *mnt,
path_get(&nd->root);
nd->inode = nd->path.dentry->d_inode;

retval = path_walk(name, nd);
if (unlikely(!retval && !audit_dummy_context() && nd->path.dentry &&
current->total_link_count = 0;

result = link_path_walk(name, nd);
if (result == -ESTALE) {
/* nd->path had been dropped */
current->total_link_count = 0;
nd->path.dentry = dentry;
nd->path.mnt = mnt;
nd->inode = dentry->d_inode;
path_get(&nd->path);
nd->flags |= LOOKUP_REVAL;
result = link_path_walk(name, nd);
}
if (unlikely(!result && !audit_dummy_context() && nd->path.dentry &&
nd->inode))
audit_inode(name, nd->path.dentry);

path_put(&nd->root);
nd->root.mnt = NULL;

return retval;
return result;
}

static struct dentry *__lookup_hash(struct qstr *name,
Expand Down Expand Up @@ -2483,24 +2457,14 @@ struct file *do_filp_open(int dfd, const char *pathname,

creat:
/* OK, have to create the file. Find the parent. */
error = path_init_rcu(dfd, pathname,
LOOKUP_PARENT | (flags & LOOKUP_REVAL), &nd);
if (error)
goto out_filp;
error = path_walk_rcu(pathname, &nd);
path_finish_rcu(&nd);
if (unlikely(error == -ECHILD || error == -ESTALE)) {
/* slower, locked walk */
if (error == -ESTALE) {
error = path_lookupat(dfd, pathname, LOOKUP_PARENT | LOOKUP_RCU, &nd);
if (unlikely(error == -ECHILD))
error = path_lookupat(dfd, pathname, LOOKUP_PARENT, &nd);
if (unlikely(error == -ESTALE)) {
reval:
flags |= LOOKUP_REVAL;
}
error = path_init(dfd, pathname,
LOOKUP_PARENT | (flags & LOOKUP_REVAL), &nd);
if (error)
goto out_filp;

error = path_walk_simple(pathname, &nd);
flags |= LOOKUP_REVAL;
error = path_lookupat(dfd, pathname,
LOOKUP_PARENT | LOOKUP_REVAL, &nd);
}
if (unlikely(error))
goto out_filp;
Expand Down

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