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Commit a2982cc9 authored by Eric W. Biederman's avatar Eric W. Biederman
Browse files

vfs: Generalize filesystem nodev handling. 



Introduce a function may_open_dev that tests MNT_NODEV and a new
superblock flab SB_I_NODEV.  Use this new function in all of the
places where MNT_NODEV was previously tested.

Add the new SB_I_NODEV s_iflag to proc, sysfs, and mqueuefs as those
filesystems should never support device nodes, and a simple superblock
flags makes that very hard to get wrong.  With SB_I_NODEV set if any
device nodes somehow manage to show up on on a filesystem those
device nodes will be unopenable.

Acked-by: default avatarSeth Forshee <seth.forshee@canonical.com>
Signed-off-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
parent 3ee69014

fs/block_dev.c

+1 −1
Original line number Diff line number Diff line
@@ -1857,7 +1857,7 @@ struct block_device *lookup_bdev(const char *pathname) 
	if (!S_ISBLK(inode->i_mode))

		goto fail;

	error = -EACCES;

	if (path.mnt->mnt_flags & MNT_NODEV)

	if (!may_open_dev(&path))

		goto fail;

	error = -ENOMEM;

	bdev = bd_acquire(inode);

fs/kernfs/mount.c

+2 −2
Original line number Diff line number Diff line
@@ -152,8 +152,8 @@ static int kernfs_fill_super(struct super_block *sb, unsigned long magic) 
	struct dentry *root;



	info->sb = sb;

	/* Userspace would break if executables appear on sysfs */

	sb->s_iflags |= SB_I_NOEXEC;

	/* Userspace would break if executables or devices appear on sysfs */

	sb->s_iflags |= SB_I_NOEXEC | SB_I_NODEV;

	sb->s_blocksize = PAGE_SIZE;

	sb->s_blocksize_bits = PAGE_SHIFT;

	sb->s_magic = magic;

fs/namei.c

+7 −1
Original line number Diff line number Diff line
@@ -2881,6 +2881,12 @@ int vfs_create(struct inode *dir, struct dentry *dentry, umode_t mode, 
}

EXPORT_SYMBOL(vfs_create);



bool may_open_dev(const struct path *path)

{

	return !(path->mnt->mnt_flags & MNT_NODEV) &&

		!(path->mnt->mnt_sb->s_iflags & SB_I_NODEV);

}



static int may_open(struct path *path, int acc_mode, int flag)

{

	struct dentry *dentry = path->dentry;
@@ -2899,7 +2905,7 @@ static int may_open(struct path *path, int acc_mode, int flag) 
		break;

	case S_IFBLK:

	case S_IFCHR:

		if (path->mnt->mnt_flags & MNT_NODEV)

		if (!may_open_dev(path))

			return -EACCES;

		/*FALLTHRU*/

	case S_IFIFO:

fs/proc/inode.c

+2 −2
Original line number Diff line number Diff line
@@ -466,8 +466,8 @@ int proc_fill_super(struct super_block *s, void *data, int silent) 
	if (!proc_parse_options(data, ns))

		return -EINVAL;



	/* User space would break if executables appear on proc */

	s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC;

	/* User space would break if executables or devices appear on proc */

	s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV;

	s->s_flags |= MS_NODIRATIME | MS_NOSUID | MS_NOEXEC;

	s->s_blocksize = 1024;

	s->s_blocksize_bits = 10;

include/linux/fs.h

+2 −0
Original line number Diff line number Diff line
@@ -1327,6 +1327,7 @@ struct mm_struct; 
/* sb->s_iflags */

#define SB_I_CGROUPWB	0x00000001	/* cgroup-aware writeback enabled */

#define SB_I_NOEXEC	0x00000002	/* Ignore executables on this fs */

#define SB_I_NODEV	0x00000004	/* Ignore devices on this fs */



/* sb->s_iflags to limit user namespace mounts */

#define SB_I_USERNS_VISIBLE		0x00000010 /* fstype already mounted */
@@ -1602,6 +1603,7 @@ extern int vfs_whiteout(struct inode *, struct dentry *); 
 */

extern void inode_init_owner(struct inode *inode, const struct inode *dir,

			umode_t mode);

extern bool may_open_dev(const struct path *path);

/*

 * VFS FS_IOC_FIEMAP helper definitions.

 */