This is a note to let you know that I've just added the patch titled
mnt: Fix a memory stomp in umount
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mnt-fix-a-memory-stomp-in-umount.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From c297abfdf15b4480704d6b566ca5ca9438b12456 Mon Sep 17 00:00:00 2001
From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Date: Thu, 18 Dec 2014 10:57:19 -0600
Subject: mnt: Fix a memory stomp in umount
From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
commit c297abfdf15b4480704d6b566ca5ca9438b12456 upstream.
While reviewing the code of umount_tree I realized that when we append
to a preexisting unmounted list we do not change pprev of the former
first item in the list.
Which means later in namespace_unlock hlist_del_init(&mnt->mnt_hash) on
the former first item of the list will stomp unmounted.first leaving
it set to some random mount point which we are likely to free soon.
This isn't likely to hit, but if it does I don't know how anyone could
track it down.
[ This happened because we don't have all the same operations for
hlist's as we do for normal doubly-linked lists. In particular,
list_splice() is easy on our standard doubly-linked lists, while
hlist_splice() doesn't exist and needs both start/end entries of the
hlist. And commit 38129a13e6e7 incorrectly open-coded that missing
hlist_splice().
We should think about making these kinds of "mindless" conversions
easier to get right by adding the missing hlist helpers - Linus ]
Fixes: 38129a13e6e71f666e0468e99fdd932a687b4d7e switch mnt_hash to hlist
Signed-off-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/namespace.c | 2 ++
1 file changed, 2 insertions(+)
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1295,6 +1295,8 @@ void umount_tree(struct mount *mnt, int
}
if (last) {
last->mnt_hash.next = unmounted.first;
+ if (unmounted.first)
+ unmounted.first->pprev = &last->mnt_hash.next;
unmounted.first = tmp_list.first;
unmounted.first->pprev = &unmounted.first;
}
Patches currently in stable-queue which might be from ebiederm@xxxxxxxxxxxx are
queue-3.14/mnt-fix-a-memory-stomp-in-umount.patch
queue-3.14/userns-unbreak-the-unprivileged-remount-tests.patch
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