From e5805b4410dcacbc9e11b6dc75368375b848e22d Mon Sep 17 00:00:00 2001
From: Daniel Rosenberg<drosen@google.com>
Date: Fri, 20  Jul  2018  23:11:40  +0000
Subject: ANDROID: sdcardfs: Change current->fs under lock

PD#SWPL-5666

Problem:
STS test fail
testPocCVE_2018_9515

Solution:
bug: 111641492 from security

Verify:
U212

Change-Id: I79e9894f94880048edaf0f7cfa2d180f65cbcf3b
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Daniel Rosenberg <drosen@google.com>
---
diff --git a/fs/sdcardfs/inode.c b/fs/sdcardfs/inode.c
index 84df23ac0..57bdc68 100644
--- a/fs/sdcardfs/inode.c
+++ b/fs/sdcardfs/inode.c
@@ -95,8 +95,10 @@ static int sdcardfs_create(struct inode *dir, struct dentry *dentry,
 		err = -ENOMEM;
 		goto out_unlock;
 	}
+	copied_fs->umask = 0;
+	task_lock(current);
 	current->fs = copied_fs;
-	current->fs->umask = 0;
+	task_unlock(current);
 	err = vfs_create2(lower_dentry_mnt, d_inode(lower_parent_dentry), lower_dentry, mode, want_excl);
 	if (err)
 		goto out;
@@ -110,7 +112,9 @@ static int sdcardfs_create(struct inode *dir, struct dentry *dentry,
 	fixup_lower_ownership(dentry, dentry->d_name.name);
 
 out:
+	task_lock(current);
 	current->fs = saved_fs;
+	task_unlock(current);
 	free_fs_struct(copied_fs);
 out_unlock:
 	unlock_dir(lower_parent_dentry);
@@ -316,8 +320,10 @@ static int sdcardfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
 		unlock_dir(lower_parent_dentry);
 		goto out_unlock;
 	}
+	copied_fs->umask = 0;
+	task_lock(current);
 	current->fs = copied_fs;
-	current->fs->umask = 0;
+	task_unlock(current);
 	err = vfs_mkdir2(lower_mnt, d_inode(lower_parent_dentry), lower_dentry, mode);
 
 	if (err) {
@@ -377,7 +383,10 @@ static int sdcardfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
 		}
 	}
 out:
+	task_lock(current);
 	current->fs = saved_fs;
+	task_unlock(current);
+
 	free_fs_struct(copied_fs);
 out_unlock:
 	sdcardfs_put_lower_path(dentry, &lower_path);
--
cgit