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55 lines
2.1 KiB
Diff
55 lines
2.1 KiB
Diff
From c88f7bbd8026761a615c9969d186ffa2a1a3da3c Mon Sep 17 00:00:00 2001
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From: "Eric W. Biederman" <ebiederm@xmission.com>
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Date: Thu, 15 Jan 2015 17:49:27 +0000
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Subject: [PATCH] mnt: Prevent pivot_root from creating a loop in the mount
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tree
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Andy Lutomirski recently demonstrated that when chroot is used to set
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the root path below the path for the new ``root'' passed to pivot_root
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the pivot_root system call succeeds and leaks mounts.
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In examining the code I see that starting with a new root that is
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below the current root in the mount tree will result in a loop in the
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mount tree after the mounts are detached and then reattached to one
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another. Resulting in all kinds of ugliness including a leak of that
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mounts involved in the leak of the mount loop.
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Prevent this problem by ensuring that the new mount is reachable from
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the current root of the mount tree.
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[Added stable cc. Fixes CVE-2014-7970. --Andy]
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Cc: stable@vger.kernel.org
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Reported-by: Andy Lutomirski <luto@amacapital.net>
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Reviewed-by: Andy Lutomirski <luto@amacapital.net>
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Link: http://lkml.kernel.org/r/87bnpmihks.fsf@x220.int.ebiederm.org
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Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Signed-off-by: Andy Lutomirski <luto@amacapital.net>
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(backported from commit 0d0826019e529f21c84687521d03f60cd241ca7d)
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CVE-2014-7970
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BugLink: http://bugs.launchpad.net/bugs/1383356
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Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
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Acked-by: Stefan Bader <stefan.bader@canonical.com>
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Acked-by: Andy Whitcroft <apw@canonical.com>
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Signed-off-by: Andy Whitcroft <apw@canonical.com>
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Change-Id: I0fe1d090eeb4765cc49401784e44a430f9585498
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---
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fs/namespace.c | 3 +++
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1 file changed, 3 insertions(+)
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diff --git a/fs/namespace.c b/fs/namespace.c
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index 912d273d970..4f47629a4e0 100644
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--- a/fs/namespace.c
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+++ b/fs/namespace.c
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@@ -2618,6 +2618,9 @@ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
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goto out4;
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} else if (!is_subdir(old.dentry, new.dentry))
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goto out4;
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+ /* make certain new is below the root */
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+ if (!is_path_reachable(new.mnt, new.dentry, &root))
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+ goto out4;
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br_write_lock(vfsmount_lock);
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detach_mnt(new.mnt, &parent_path);
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detach_mnt(root.mnt, &root_parent);
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