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/namei.c b/fs/namei.c
index 6a82fb7..757a3272 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2881,6 +2881,12 @@
}
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 @@
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: