sdcardfs: override umask on mkdir and create
The mode on files created on the lower fs should
not be affected by the umask of the calling
task's fs_struct. Instead, we create a copy
and modify it as needed. This also lets us avoid
the string shenanigans around .nomedia files.
Bug: 27992761
Change-Id: Ia3a6e56c24c6e19b3b01c1827e46403bb71c2f4c
Signed-off-by: Daniel Rosenberg <drosen@google.com>
diff --git a/fs/fs_struct.c b/fs/fs_struct.c
index e159e68..90f76a3 100644
--- a/fs/fs_struct.c
+++ b/fs/fs_struct.c
@@ -140,6 +140,7 @@
return fs;
}
+EXPORT_SYMBOL_GPL(copy_fs_struct);
int unshare_fs_struct(void)
{
struct fs_struct *fs = current->fs;
diff --git a/fs/sdcardfs/inode.c b/fs/sdcardfs/inode.c
index 3c84051..32034b1 100644
--- a/fs/sdcardfs/inode.c
+++ b/fs/sdcardfs/inode.c
@@ -19,6 +19,7 @@
*/
#include "sdcardfs.h"
+#include <linux/fs_struct.h>
/* Do not directly use this function. Use OVERRIDE_CRED() instead. */
const struct cred * override_fsids(struct sdcardfs_sb_info* sbi)
@@ -56,6 +57,8 @@
struct dentry *lower_parent_dentry = NULL;
struct path lower_path;
const struct cred *saved_cred = NULL;
+ struct fs_struct *saved_fs;
+ struct fs_struct *copied_fs;
if(!check_caller_access_to_name(dir, dentry->d_name.name)) {
printk(KERN_INFO "%s: need to check the caller's gid in packages.list\n"
@@ -78,6 +81,12 @@
/* set last 16bytes of mode field to 0664 */
mode = (mode & S_IFMT) | 00664;
+
+ /* temporarily change umask for lower fs write */
+ saved_fs = current->fs;
+ copied_fs = copy_fs_struct(current->fs);
+ current->fs = copied_fs;
+ current->fs->umask = 0;
err = vfs_create(lower_parent_dentry->d_inode, lower_dentry, mode, nd);
if (err)
goto out;
@@ -90,6 +99,8 @@
out:
mnt_drop_write(lower_path.mnt);
+ current->fs = saved_fs;
+ free_fs_struct(copied_fs);
out_unlock:
unlock_dir(lower_parent_dentry);
sdcardfs_put_lower_path(dentry, &lower_path);
@@ -267,11 +278,9 @@
struct sdcardfs_sb_info *sbi = SDCARDFS_SB(dentry->d_sb);
const struct cred *saved_cred = NULL;
struct sdcardfs_inode_info *pi = SDCARDFS_I(dir);
- char *page_buf;
- char *nomedia_dir_name;
- char *nomedia_fullpath;
- int fullpath_namelen;
int touch_err = 0;
+ struct fs_struct *saved_fs;
+ struct fs_struct *copied_fs;
if(!check_caller_access_to_name(dir, dentry->d_name.name)) {
printk(KERN_INFO "%s: need to check the caller's gid in packages.list\n"
@@ -302,6 +311,12 @@
/* set last 16bytes of mode field to 0775 */
mode = (mode & S_IFMT) | 00775;
+
+ /* temporarily change umask for lower fs write */
+ saved_fs = current->fs;
+ copied_fs = copy_fs_struct(current->fs);
+ current->fs = copied_fs;
+ current->fs->umask = 0;
err = vfs_mkdir(lower_parent_dentry->d_inode, lower_dentry, mode);
if (err)
@@ -342,43 +357,18 @@
/* When creating /Android/data and /Android/obb, mark them as .nomedia */
if (make_nomedia_in_obb ||
((pi->perm == PERM_ANDROID) && (!strcasecmp(dentry->d_name.name, "data")))) {
-
- page_buf = (char *)__get_free_page(GFP_KERNEL);
- if (!page_buf) {
- printk(KERN_ERR "sdcardfs: failed to allocate page buf\n");
- goto out;
- }
-
- nomedia_dir_name = d_absolute_path(&lower_path, page_buf, PAGE_SIZE);
- if (IS_ERR(nomedia_dir_name)) {
- free_page((unsigned long)page_buf);
- printk(KERN_ERR "sdcardfs: failed to get .nomedia dir name\n");
- goto out;
- }
-
- fullpath_namelen = page_buf + PAGE_SIZE - nomedia_dir_name - 1;
- fullpath_namelen += strlen("/.nomedia");
- nomedia_fullpath = kzalloc(fullpath_namelen + 1, GFP_KERNEL);
- if (!nomedia_fullpath) {
- free_page((unsigned long)page_buf);
- printk(KERN_ERR "sdcardfs: failed to allocate .nomedia fullpath buf\n");
- goto out;
- }
-
- strcpy(nomedia_fullpath, nomedia_dir_name);
- free_page((unsigned long)page_buf);
- strcat(nomedia_fullpath, "/.nomedia");
- touch_err = touch(nomedia_fullpath, 0664);
+ set_fs_pwd(current->fs, &lower_path);
+ touch_err = touch(".nomedia", 0664);
if (touch_err) {
- printk(KERN_ERR "sdcardfs: failed to touch(%s): %d\n",
- nomedia_fullpath, touch_err);
- kfree(nomedia_fullpath);
+ printk(KERN_ERR "sdcardfs: failed to create .nomedia in %s: %d\n",
+ lower_path.dentry->d_name.name, touch_err);
goto out;
}
- kfree(nomedia_fullpath);
}
out:
mnt_drop_write(lower_path.mnt);
+ current->fs = saved_fs;
+ free_fs_struct(copied_fs);
out_unlock:
unlock_dir(lower_parent_dentry);
sdcardfs_put_lower_path(dentry, &lower_path);