Miaohe Lin 025a7ccfb7 mm/mlock: fix two bugs in user_shm_lock()
commit e97824ff66 upstream.

user_shm_lock forgets to set allowed to 0 when get_ucounts fails. So the
later user_shm_unlock might do the extra dec_rlimit_ucounts. Also in the
RLIM_INFINITY case, user_shm_lock will success regardless of the value of
memlock where memblock == LONG_MAX && !capable(CAP_IPC_LOCK) should fail.
Fix all of these by changing the code to leave lock_limit at ULONG_MAX aka
RLIM_INFINITY, leave "allowed" initialized to 0 and remove the special case
of RLIM_INFINITY as nothing can be greater than ULONG_MAX.

Credit goes to Eric W. Biederman for proposing simplifying the code and
thus catching the later bug.

Fixes: d7c9e99aee ("Reimplement RLIMIT_MEMLOCK on top of ucounts")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: stable@vger.kernel.org
v1: https://lkml.kernel.org/r/20220310132417.41189-1-linmiaohe@huawei.com
v2: https://lkml.kernel.org/r/20220314064039.62972-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20220322080918.59861-1-linmiaohe@huawei.com
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-04-08 14:22:52 +02:00
2021-10-18 20:22:03 -10:00
2022-03-28 09:58:46 +02:00

Linux kernel
============

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