diff options
| author | Eric W. Biederman <ebiederm@xmission.com> | 2013-03-22 03:10:15 -0700 |
|---|---|---|
| committer | Eric W. Biederman <ebiederm@xmission.com> | 2013-03-27 07:50:04 -0700 |
| commit | 90563b198e4c6674c63672fae1923da467215f45 (patch) | |
| tree | aa8528c1c23dccbeca409059ec5f5d21ca1318bf | |
| parent | 3151527ee007b73a0ebd296010f1c0454a919c7d (diff) | |
vfs: Add a mount flag to lock read only bind mounts
When a read-only bind mount is copied from mount namespace in a higher
privileged user namespace to a mount namespace in a lesser privileged
user namespace, it should not be possible to remove the the read-only
restriction.
Add a MNT_LOCK_READONLY mount flag to indicate that a mount must
remain read-only.
CC: stable@vger.kernel.org
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
| -rw-r--r-- | fs/namespace.c | 3 | ||||
| -rw-r--r-- | include/linux/mount.h | 2 |
2 files changed, 5 insertions, 0 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index a3035223d42..8505b5ece5d 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1713,6 +1713,9 @@ static int change_mount_flags(struct vfsmount *mnt, int ms_flags) if (readonly_request == __mnt_is_readonly(mnt)) return 0; + if (mnt->mnt_flags & MNT_LOCK_READONLY) + return -EPERM; + if (readonly_request) error = mnt_make_readonly(real_mount(mnt)); else diff --git a/include/linux/mount.h b/include/linux/mount.h index d7029f4a191..73005f9957e 100644 --- a/include/linux/mount.h +++ b/include/linux/mount.h @@ -47,6 +47,8 @@ struct mnt_namespace; #define MNT_INTERNAL 0x4000 +#define MNT_LOCK_READONLY 0x400000 + struct vfsmount { struct dentry *mnt_root; /* root of the mounted tree */ struct super_block *mnt_sb; /* pointer to superblock */ |