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authorEric W. Biederman <ebiederm@xmission.com>2013-03-22 03:10:15 -0700
committerEric W. Biederman <ebiederm@xmission.com>2013-03-27 07:50:04 -0700
commit90563b198e4c6674c63672fae1923da467215f45 (patch)
treeaa8528c1c23dccbeca409059ec5f5d21ca1318bf /fs
parent3151527ee007b73a0ebd296010f1c0454a919c7d (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>
Diffstat (limited to 'fs')
-rw-r--r--fs/namespace.c3
1 files changed, 3 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