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Commit e520ac67 authored by Daniel Rosenberg's avatar Daniel Rosenberg
Browse files

ANDROID: 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: default avatarDaniel Rosenberg <drosen@google.com>
parent c8512dd6

fs/fs_struct.c

+1 −0
Original line number Diff line number Diff line
@@ -128,6 +128,7 @@ struct fs_struct *copy_fs_struct(struct fs_struct *old) 
	}

	return fs;

}

EXPORT_SYMBOL_GPL(copy_fs_struct);



int unshare_fs_struct(void)

{

fs/sdcardfs/inode.c

+35 −35
Original line number Diff line number Diff line
@@ -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(d_inode(lower_parent_dentry), 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, d_inode(lower_parent_dentry));



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(d_inode(lower_parent_dentry), 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: