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authorAl Viro <viro@zeniv.linux.org.uk>2011-03-14 21:54:55 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2011-03-15 17:16:25 -0400
commitb356379a020bb7197603118bb1cbc903963aa198 (patch)
tree834722d850b2f6a82a07464680244847ed477755
parentce0525449da56444948c368f52e10f3db0465338 (diff)
Turn resolution of trailing symlinks iterative everywhere
The last remaining place (resolution of nested symlink) converted to the loop of the same kind we have in path_lookupat() and path_openat(). Note that we still *do* have a recursion in pathname resolution; can't avoid it, really. However, it's strictly for nested symlinks now - i.e. ones in the middle of a pathname. link_path_walk() has lost the tail now - it always walks everything except the last component. do_follow_link() renamed to nested_symlink() and moved down. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/namei.c104
1 files changed, 50 insertions, 54 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 9575d003969..017c3fa3a08 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -779,40 +779,6 @@ __do_follow_link(const struct path *link, struct nameidata *nd, void **p)
return error;
}
-/*
- * This limits recursive symlink follows to 8, while
- * limiting consecutive symlinks to 40.
- *
- * Without that kind of total limit, nasty chains of consecutive
- * symlinks can cause almost arbitrarily long lookups.
- */
-static inline int do_follow_link(struct path *path, struct nameidata *nd)
-{
- void *cookie;
- int err = -ELOOP;
-
- if (current->link_count >= MAX_NESTED_LINKS)
- goto loop;
- if (current->total_link_count >= 40)
- goto loop;
- BUG_ON(nd->depth >= MAX_NESTED_LINKS);
- cond_resched();
- current->link_count++;
- current->total_link_count++;
- nd->depth++;
- err = __do_follow_link(path, nd, &cookie);
- if (!IS_ERR(cookie) && path->dentry->d_inode->i_op->put_link)
- path->dentry->d_inode->i_op->put_link(path->dentry, nd, cookie);
- path_put(path);
- current->link_count--;
- nd->depth--;
- return err;
-loop:
- path_put_conditional(path, nd);
- path_put(&nd->path);
- return err;
-}
-
static int follow_up_rcu(struct path *path)
{
struct vfsmount *parent;
@@ -1367,6 +1333,52 @@ static inline int walk_component(struct nameidata *nd, struct path *path,
}
/*
+ * This limits recursive symlink follows to 8, while
+ * limiting consecutive symlinks to 40.
+ *
+ * Without that kind of total limit, nasty chains of consecutive
+ * symlinks can cause almost arbitrarily long lookups.
+ */
+static inline int nested_symlink(struct path *path, struct nameidata *nd)
+{
+ int res;
+
+ BUG_ON(nd->depth >= MAX_NESTED_LINKS);
+ if (unlikely(current->link_count >= MAX_NESTED_LINKS)) {
+ path_put_conditional(path, nd);
+ path_put(&nd->path);
+ return -ELOOP;
+ }
+
+ nd->depth++;
+ current->link_count++;
+
+ do {
+ struct path link = *path;
+ void *cookie;
+ if (unlikely(current->total_link_count >= 40)) {
+ path_put_conditional(path, nd);
+ path_put(&nd->path);
+ res = -ELOOP;
+ break;
+ }
+ cond_resched();
+ current->total_link_count++;
+ res = __do_follow_link(&link, nd, &cookie);
+ if (!res)
+ res = walk_component(nd, path, &nd->last,
+ nd->last_type, LOOKUP_FOLLOW);
+ if (!IS_ERR(cookie) && link.dentry->d_inode->i_op->put_link)
+ link.dentry->d_inode->i_op->put_link(link.dentry, nd, cookie);
+ path_put(&link);
+ } while (res > 0);
+
+ current->link_count--;
+ nd->depth--;
+ return res;
+}
+
+/*
* Name resolution.
* This is the basic name resolution function, turning a pathname into
* the final dentry. We expect 'base' to be positive and a directory.
@@ -1385,9 +1397,6 @@ static int link_path_walk(const char *name, struct nameidata *nd)
if (!*name)
return 0;
- if (nd->depth)
- lookup_flags = LOOKUP_FOLLOW | (nd->flags & LOOKUP_CONTINUE);
-
/* At this point we know we have a real path component. */
for(;;) {
unsigned long hash;
@@ -1440,14 +1449,14 @@ static int link_path_walk(const char *name, struct nameidata *nd)
goto last_component;
while (*++name == '/');
if (!*name)
- goto last_with_slashes;
+ goto last_component;
err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
if (err < 0)
return err;
if (err) {
- err = do_follow_link(&next, nd);
+ err = nested_symlink(&next, nd);
if (err)
return err;
}
@@ -1457,24 +1466,11 @@ static int link_path_walk(const char *name, struct nameidata *nd)
continue;
/* here ends the main loop */
-last_with_slashes:
- lookup_flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY;
last_component:
/* Clear LOOKUP_CONTINUE iff it was previously unset */
nd->flags &= lookup_flags | ~LOOKUP_CONTINUE;
- if (lookup_flags & LOOKUP_PARENT) {
- nd->last = this;
- nd->last_type = type;
- return 0;
- }
- err = walk_component(nd, &next, &this, type, LOOKUP_FOLLOW);
- if (err < 0)
- return err;
- if (err) {
- err = do_follow_link(&next, nd);
- if (err)
- return err;
- }
+ nd->last = this;
+ nd->last_type = type;
return 0;
}
terminate_walk(nd);