| Date | Thu, 11 Apr 2013 16:26:53 -0400 | From | Steven Rostedt <> | Subject | [ 110/171 ] vfs: Add a mount flag to lock read only bind mounts |
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3.6.11.2 stable review patch. If anyone has any objections, please let me know.
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From: "Eric W. Biederman" <ebiederm@xmission.com>
[ Upstream commit 90563b198e4c6674c63672fae1923da467215f45 ]
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> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> --- fs/namespace.c | 3 +++ include/linux/mount.h | 2 ++ 2 files changed, 5 insertions(+)
diff --git a/fs/namespace.c b/fs/namespace.c index c48b0d3..48c7edb 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1702,6 +1702,9 @@ 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 d7029f4..73005f9 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 */ -- 1.7.10.4
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