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-rw-r--r--fs/namei.c71
1 files changed, 71 insertions, 0 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 45c702edce3c..1067f7a0287a 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2272,6 +2272,8 @@ EXPORT_SYMBOL(vfs_path_lookup);
*
* Note that this routine is purely a helper for filesystem usage and should
* not be called by generic code.
+ *
+ * The caller must hold base->i_mutex.
*/
struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
{
@@ -2315,6 +2317,75 @@ struct dentry *lookup_one_len(const char *name, struct dentry *base, int len)
}
EXPORT_SYMBOL(lookup_one_len);
+/**
+ * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
+ * @name: pathname component to lookup
+ * @base: base directory to lookup from
+ * @len: maximum length @len should be interpreted to
+ *
+ * Note that this routine is purely a helper for filesystem usage and should
+ * not be called by generic code.
+ *
+ * Unlike lookup_one_len, it should be called without the parent
+ * i_mutex held, and will take the i_mutex itself if necessary.
+ */
+struct dentry *lookup_one_len_unlocked(const char *name,
+ struct dentry *base, int len)
+{
+ struct qstr this;
+ unsigned int c;
+ int err;
+ struct dentry *ret;
+
+ this.name = name;
+ this.len = len;
+ this.hash = full_name_hash(name, len);
+ if (!len)
+ return ERR_PTR(-EACCES);
+
+ if (unlikely(name[0] == '.')) {
+ if (len < 2 || (len == 2 && name[1] == '.'))
+ return ERR_PTR(-EACCES);
+ }
+
+ while (len--) {
+ c = *(const unsigned char *)name++;
+ if (c == '/' || c == '\0')
+ return ERR_PTR(-EACCES);
+ }
+ /*
+ * See if the low-level filesystem might want
+ * to use its own hash..
+ */
+ if (base->d_flags & DCACHE_OP_HASH) {
+ int err = base->d_op->d_hash(base, &this);
+ if (err < 0)
+ return ERR_PTR(err);
+ }
+
+ err = inode_permission(base->d_inode, MAY_EXEC);
+ if (err)
+ return ERR_PTR(err);
+
+ /*
+ * __d_lookup() is used to try to get a quick answer and avoid the
+ * mutex. A false-negative does no harm.
+ */
+ ret = __d_lookup(base, &this);
+ if (ret && unlikely(ret->d_flags & DCACHE_OP_REVALIDATE)) {
+ dput(ret);
+ ret = NULL;
+ }
+ if (ret)
+ return ret;
+
+ mutex_lock(&base->d_inode->i_mutex);
+ ret = __lookup_hash(&this, base, 0);
+ mutex_unlock(&base->d_inode->i_mutex);
+ return ret;
+}
+EXPORT_SYMBOL(lookup_one_len_unlocked);
+
int user_path_at_empty(int dfd, const char __user *name, unsigned flags,
struct path *path, int *empty)
{