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| 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 /fs/proc/proc_sysctl.c | |
| parent | Linux 4.11-rc1 (diff) | |
| download | linux-dev-040757f738e13caaa9c5078bca79aa97e11dde88.tar.xz linux-dev-040757f738e13caaa9c5078bca79aa97e11dde88.zip | |
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 'fs/proc/proc_sysctl.c')
0 files changed, 0 insertions, 0 deletions