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| author | Eric W. Biederman <ebiederm@xmission.com> | 2017-03-05 15:03:22 -0600 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-03-18 19:18:38 +0800 |
| commit | da603aadd53a9a5ac18eaac09f61a5af74b9a52e (patch) | |
| tree | 10b53cbf84789562805c5109848f8378c6f78b54 /include | |
| parent | b7e9ef5cf4d9562c3a1a15beee269a0b18f71976 (diff) | |
| download | linux-stable-da603aadd53a9a5ac18eaac09f61a5af74b9a52e.tar.gz linux-stable-da603aadd53a9a5ac18eaac09f61a5af74b9a52e.tar.bz2 linux-stable-da603aadd53a9a5ac18eaac09f61a5af74b9a52e.zip | |
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]; }; |