The commit is pushed to "branch-rh7-3.10.0-327.10.1.vz7.12.x-ovz" and will
appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.10.1.vz7.12.1
------>
commit f1af1e286c5d5dbd5afcfba031d9ee1398a33991
Author: Pavel Tikhomirov <[email protected]>
Date: Tue Mar 15 20:04:11 2016 +0400
ms/mnt: Only change user settable mount flags in remount
ms commit a6138db815df ("mnt: Only change user settable mount flags in
remount")
Kenton Varda <[email protected]> discovered that by remounting a
read-only bind mount read-only in a user namespace the
MNT_LOCK_READONLY bit would be cleared, allowing an unprivileged user
to the remount a read-only mount read-write.
Correct this by replacing the mask of mount flags to preserve
with a mask of mount flags that may be changed, and preserve
all others. This ensures that any future bugs with this mask and
remount will fail in an easy to detect way where new mount flags
simply won't change.
Cc: [email protected]
Acked-by: Serge E. Hallyn <[email protected]>
Signed-off-by: "Eric W. Biederman" <[email protected]>
Signed-off-by: Pavel Tikhomirov <[email protected]>
Found during investigation of
https://jira.sw.ru/browse/PSBM-43294
---
fs/namespace.c | 2 +-
include/linux/mount.h | 4 +++-
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index 787619b..dba0c40 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2011,7 +2011,7 @@ static int do_remount(struct path *path, int flags, int
mnt_flags,
err = do_check_and_remount_sb(sb, flags, data);
if (!err) {
br_write_lock(&vfsmount_lock);
- mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK;
+ mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
mnt->mnt.mnt_flags = mnt_flags;
br_write_unlock(&vfsmount_lock);
}
diff --git a/include/linux/mount.h b/include/linux/mount.h
index f8285ec..d1e3811 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -42,7 +42,9 @@ struct mnt_namespace;
* flag, consider how it interacts with shared mounts.
*/
#define MNT_SHARED_MASK (MNT_UNBINDABLE)
-#define MNT_PROPAGATION_MASK (MNT_SHARED | MNT_UNBINDABLE)
+#define MNT_USER_SETTABLE_MASK (MNT_NOSUID | MNT_NODEV | MNT_NOEXEC \
+ | MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME \
+ | MNT_READONLY)
#define MNT_INTERNAL_FLAGS (MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL | \
MNT_MARKED)
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