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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>
This commit is contained in:
Daniel Rosenberg 2016-04-13 16:38:34 -07:00 committed by LuK1337
parent 94a4aba731
commit bbb9560c0e
2 changed files with 36 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
fs/fs_struct.c
View File

@ -127,6 +127,7 @@ struct fs_struct *copy_fs_struct(struct fs_struct *old)
}
return fs;
}
EXPORT_SYMBOL_GPL(copy_fs_struct);
int unshare_fs_struct(void)
{

70
fs/sdcardfs/inode.c
View File

@ -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 @@ static int sdcardfs_create(struct inode *dir, struct dentry *dentry,
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"
@ -74,6 +77,16 @@ static int sdcardfs_create(struct inode *dir, struct dentry *dentry,
/* 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);
if (!copied_fs) {
err = -ENOMEM;
goto out_unlock;
}
current->fs = copied_fs;
current->fs->umask = 0;
err = vfs_create(lower_parent_dentry->d_inode, lower_dentry, mode, want_excl);
if (err)
goto out;
@ -85,6 +98,9 @@ static int sdcardfs_create(struct inode *dir, struct dentry *dentry,
fsstack_copy_inode_size(dir, lower_parent_dentry->d_inode);
out:
current->fs = saved_fs;
free_fs_struct(copied_fs);
out_unlock:
unlock_dir(lower_parent_dentry);
sdcardfs_put_lower_path(dentry, &lower_path);
REVERT_CRED(saved_cred);
@ -245,11 +261,9 @@ static int sdcardfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
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"
@ -276,6 +290,16 @@ static int sdcardfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
/* 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);
if (!copied_fs) {
err = -ENOMEM;
goto out_unlock;
}
current->fs = copied_fs;
current->fs->umask = 0;
err = vfs_mkdir(lower_parent_dentry->d_inode, lower_dentry, mode);
if (err)
@ -316,42 +340,18 @@ static int sdcardfs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode
/* 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:
current->fs = saved_fs;
free_fs_struct(copied_fs);
out_unlock:
unlock_dir(lower_parent_dentry);
sdcardfs_put_lower_path(dentry, &lower_path);
out_revert: