GitHub-Mirror/Star64_linux
2
0
Fork 0
mirror of https://github.com/Fishwaldo/Star64_linux.git synced 2025-07-04 13:21:45 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions

ucount: Remove the atomicity from ucount->count

Browse source 
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: f6b2db1a3e ("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>
This commit is contained in:
Eric W. Biederman 2017-03-05 15:03:22 -06:00
parent c1ae3cfa0e
commit 040757f738
2 changed files with 12 additions and 8 deletions
Download patch file Download diff file Expand all files Collapse all files

2
include/linux/user_namespace.h
View file

@ -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];
};