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 84df23a..57bdc68 100644 (file)
--- 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);