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: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
diff --git a/fs/kernfs/mount.c b/fs/kernfs/mount.c
index 1443df6..b3d73ad 100644
--- a/fs/kernfs/mount.c
+++ b/fs/kernfs/mount.c
@@ -152,8 +152,8 @@
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;