1 files changed, 27 insertions, 32 deletions

diff --git a/fs/open.c b/fs/open.c
index 83cdb9dee0c1..c0a426d5766c 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -425,39 +425,33 @@ out:
  */
 asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode)
 {
+        const struct cred *old_cred;
+        struct cred *override_cred;
         struct path path;
         struct inode *inode;
-        int old_fsuid, old_fsgid;
-        kernel_cap_t uninitialized_var(old_cap);  /* !SECURE_NO_SETUID_FIXUP */
         int res;
 
         if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
                 return -EINVAL;
 
-        old_fsuid = current->fsuid;
-        old_fsgid = current->fsgid;
+        override_cred = prepare_creds();
+        if (!override_cred)
+                return -ENOMEM;
 
-        current->fsuid = current->uid;
-        current->fsgid = current->gid;
+        override_cred->fsuid = override_cred->uid;
+        override_cred->fsgid = override_cred->gid;
 
         if (!issecure(SECURE_NO_SETUID_FIXUP)) {
-                /*
-                 * Clear the capabilities if we switch to a non-root user
-                 */
-#ifndef CONFIG_SECURITY_FILE_CAPABILITIES
-                /*
-                 * FIXME: There is a race here against sys_capset.  The
-                 * capabilities can change yet we will restore the old
-                 * value below.  We should hold task_capabilities_lock,
-                 * but we cannot because user_path_at can sleep.
-                 */
-#endif /* ndef CONFIG_SECURITY_FILE_CAPABILITIES */
-                if (current->uid)
-                        old_cap = cap_set_effective(__cap_empty_set);
+                /* Clear the capabilities if we switch to a non-root user */
+                if (override_cred->uid)
+                        cap_clear(override_cred->cap_effective);
                 else
-                        old_cap = cap_set_effective(current->cap_permitted);
+                        override_cred->cap_effective =
+                                override_cred->cap_permitted;
         }
 
+        old_cred = override_creds(override_cred);
+
         res = user_path_at(dfd, filename, LOOKUP_FOLLOW, &path);
         if (res)
                 goto out;
@@ -494,12 +488,8 @@ asmlinkage long sys_faccessat(int dfd, const char __user *filename, int mode)
 out_path_release:
         path_put(&path);
 out:
-        current->fsuid = old_fsuid;
-        current->fsgid = old_fsgid;
-
-        if (!issecure(SECURE_NO_SETUID_FIXUP))
-                cap_set_effective(old_cap);
-
+        revert_creds(old_cred);
+        put_cred(override_cred);
         return res;
 }
 
@@ -792,7 +782,8 @@ static inline int __get_file_write_access(struct inode *inode,
 
 static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
                                         int flags, struct file *f,
-                                        int (*open)(struct inode *, struct file *))
+                                        int (*open)(struct inode *, struct file *),
+                                        const struct cred *cred)
 {
         struct inode *inode;
         int error;
@@ -816,7 +807,7 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
         f->f_op = fops_get(inode->i_fop);
         file_move(f, &inode->i_sb->s_files);
 
-        error = security_dentry_open(f);
+        error = security_dentry_open(f, cred);
         if (error)
                 goto cleanup_all;
 
@@ -891,6 +882,8 @@ cleanup_file:
 struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry,
                 int (*open)(struct inode *, struct file *))
 {
+        const struct cred *cred = current_cred();
+
         if (IS_ERR(nd->intent.open.file))
                 goto out;
         if (IS_ERR(dentry))
@@ -898,7 +891,7 @@ struct file *lookup_instantiate_filp(struct nameidata *nd, struct dentry *dentry
         nd->intent.open.file = __dentry_open(dget(dentry), mntget(nd->path.mnt),
                                              nd->intent.open.flags - 1,
                                              nd->intent.open.file,
-                                             open);
+                                             open, cred);
 out:
         return nd->intent.open.file;
 out_err:
@@ -917,6 +910,7 @@ EXPORT_SYMBOL_GPL(lookup_instantiate_filp);
  */
 struct file *nameidata_to_filp(struct nameidata *nd, int flags)
 {
+        const struct cred *cred = current_cred();
         struct file *filp;
 
         /* Pick up the filp from the open intent */
@@ -924,7 +918,7 @@ struct file *nameidata_to_filp(struct nameidata *nd, int flags)
         /* Has the filesystem initialised the file for us? */
         if (filp->f_path.dentry == NULL)
                 filp = __dentry_open(nd->path.dentry, nd->path.mnt, flags, filp,
-                                     NULL);
+                                     NULL, cred);
         else
                 path_put(&nd->path);
         return filp;
@@ -934,7 +928,8 @@ struct file *nameidata_to_filp(struct nameidata *nd, int flags)
  * dentry_open() will have done dput(dentry) and mntput(mnt) if it returns an
  * error.
  */
-struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags)
+struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags,
+                         const struct cred *cred)
 {
         int error;
         struct file *f;
@@ -959,7 +954,7 @@ struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags)
                 return ERR_PTR(error);
         }
 
-        return __dentry_open(dentry, mnt, flags, f, NULL);
+        return __dentry_open(dentry, mnt, flags, f, NULL, cred);
 }
 EXPORT_SYMBOL(dentry_open);