diff options
| author | Eric W. Biederman <ebiederm@xmission.com> | 2017-03-05 15:03:22 -0600 |
|---|---|---|
| committer | Eric W. Biederman <ebiederm@xmission.com> | 2017-03-06 15:26:37 -0600 |
| commit | 040757f738e13caaa9c5078bca79aa97e11dde88 (patch) | |
| tree | d2254d13ea030261eb3d894f8d7c3401f3e8a5e3 /include | |
| parent | c1ae3cfa0e89fa1a7ecc4c99031f5e9ae99d9201 (diff) | |
ucount: Remove the atomicity from ucount->count
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.
Cc: stable@vger.kernel.org
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>
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 be765234c0a2..32354b4b4b2b 100644 --- a/include/linux/user_namespace.h +++ b/include/linux/user_namespace.h @@ -72,7 +72,7 @@ struct ucounts { struct hlist_node node; struct user_namespace *ns; kuid_t uid; - atomic_t count; + int count; atomic_t ucount[UCOUNT_COUNTS]; }; |