unimore/kernel-hacking-2024-linux-steffo
unimore/kernel-hacking-2024-linux-steffo
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vfs: Add a mount flag to lock read only bind mounts

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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>
This commit is contained in:
Eric W. Biederman 2013-03-22 03:10:15 -07:00
parent 3151527ee0
commit 90563b198e
2 changed files with 5 additions and 0 deletions
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3
fs/namespace.c
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@ -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

2
include/linux/mount.h
View file

@ -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 */