diff options
| author | Eric W. Biederman <ebiederm@xmission.com> | 2017-03-06 00:03:22 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-03-18 14:14:29 +0300 |
| commit | ee6f7ee1e4cdb0098fee4593ddf11ca6028abef2 (patch) | |
| tree | 3c469849bf880367cc69d071cbd90160e7909285 /include | |
| parent | 8bb208d02accfe50cee2a9b5db3ea9da49a208b3 (diff) | |
| download | linux-ee6f7ee1e4cdb0098fee4593ddf11ca6028abef2.tar.xz | |
ucount: Remove the atomicity from ucount->count
commit 040757f738e13caaa9c5078bca79aa97e11dde88 upstream.
Always increment/decrement ucount->count under the ucounts_lock. The
increments are there already and moving the decrements there means the
locking logic of the code is simpler. This simplification in the
locking logic fixes a race between put_ucounts and get_ucounts that
could result in a use-after-free because the count could go zero then
be found by get_ucounts and then be freed by put_ucounts.
A bug presumably this one was found by a combination of syzkaller and
KASAN. JongWhan Kim reported the syzkaller failure and Dmitry Vyukov
spotted the race in the code.
Fixes: f6b2db1a3e8d ("userns: Make the count of user namespaces per user")
Reported-by: JongHwan Kim <zzoru007@gmail.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Andrei Vagin <avagin@gmail.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/user_namespace.h | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h index eb209d4523f5..dc797739f164 100644 --- a/include/linux/user_namespace.h +++ b/include/linux/user_namespace.h @@ -65,7 +65,7 @@ struct ucounts { struct hlist_node node; struct user_namespace *ns; kuid_t uid; - atomic_t count; + int count; atomic_t ucount[UCOUNT_COUNTS]; }; |