Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932333AbbGPCEu (ORCPT ); Wed, 15 Jul 2015 22:04:50 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:55521 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754436AbbGPBK3 (ORCPT ); Wed, 15 Jul 2015 21:10:29 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: "Eric W. Biederman" , Kamal Mostafa Subject: [PATCH 3.19.y-ckt 077/251] mnt: Modify fs_fully_visible to deal with locked ro nodev and atime Date: Wed, 15 Jul 2015 18:06:38 -0700 Message-Id: <1437008972-9140-78-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1437008972-9140-1-git-send-email-kamal@canonical.com> References: <1437008972-9140-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.19 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3462 Lines: 101 3.19.8-ckt4 -stable review patch. If anyone has any objections, please let me know. ------------------ From: "Eric W. Biederman" commit 8c6cf9cc829fcd0b179b59f7fe288941d0e31108 upstream. Ignore an existing mount if the locked readonly, nodev or atime attributes are less permissive than the desired attributes of the new mount. On success ensure the new mount locks all of the same readonly, nodev and atime attributes as the old mount. The nosuid and noexec attributes are not checked here as this change is destined for stable and enforcing those attributes causes a regression in lxc and libvirt-lxc where those applications will not start and there are no known executables on sysfs or proc and no known way to create exectuables without code modifications Fixes: e51db73532955 ("userns: Better restrictions on when proc and sysfs can be mounted") Signed-off-by: "Eric W. Biederman" Signed-off-by: Kamal Mostafa --- fs/namespace.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 7fd1659..34669cc 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -2293,7 +2293,7 @@ unlock: return err; } -static bool fs_fully_visible(struct file_system_type *fs_type); +static bool fs_fully_visible(struct file_system_type *fs_type, int *new_mnt_flags); /* * create a new mount for userspace and request it to be added into the @@ -2327,7 +2327,7 @@ static int do_new_mount(struct path *path, const char *fstype, int flags, mnt_flags |= MNT_NODEV | MNT_LOCK_NODEV; } if (type->fs_flags & FS_USERNS_VISIBLE) { - if (!fs_fully_visible(type)) + if (!fs_fully_visible(type, &mnt_flags)) return -EPERM; } } @@ -3131,9 +3131,10 @@ bool current_chrooted(void) return chrooted; } -static bool fs_fully_visible(struct file_system_type *type) +static bool fs_fully_visible(struct file_system_type *type, int *new_mnt_flags) { struct mnt_namespace *ns = current->nsproxy->mnt_ns; + int new_flags = *new_mnt_flags; struct mount *mnt; bool visible = false; @@ -3152,6 +3153,19 @@ static bool fs_fully_visible(struct file_system_type *type) if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root) continue; + /* Verify the mount flags are equal to or more permissive + * than the proposed new mount. + */ + if ((mnt->mnt.mnt_flags & MNT_LOCK_READONLY) && + !(new_flags & MNT_READONLY)) + continue; + if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) && + !(new_flags & MNT_NODEV)) + continue; + if ((mnt->mnt.mnt_flags & MNT_LOCK_ATIME) && + ((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK))) + continue; + /* This mount is not fully visible if there are any child mounts * that cover anything except for empty directories. */ @@ -3162,6 +3176,10 @@ static bool fs_fully_visible(struct file_system_type *type) if (inode->i_nlink > 2) goto next; } + /* Preserve the locked attributes */ + *new_mnt_flags |= mnt->mnt.mnt_flags & (MNT_LOCK_READONLY | \ + MNT_LOCK_NODEV | \ + MNT_LOCK_ATIME); visible = true; goto found; next: ; -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/