From e97824ff663ce3509fe040431c713182c2f058b1 Mon Sep 17 00:00:00 2001 From: Miaohe Lin Date: Tue, 22 Mar 2022 16:09:18 +0800 Subject: mm/mlock: fix two bugs in user_shm_lock() 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: d7c9e99aee48 ("Reimplement RLIMIT_MEMLOCK on top of ucounts") Signed-off-by: Miaohe Lin 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 --- mm/mlock.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) (limited to 'mm/mlock.c') diff --git a/mm/mlock.c b/mm/mlock.c index 25934e7db3e1..37f969ec68fa 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -827,13 +827,12 @@ int user_shm_lock(size_t size, struct ucounts *ucounts) locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT; lock_limit = rlimit(RLIMIT_MEMLOCK); - if (lock_limit == RLIM_INFINITY) - allowed = 1; - lock_limit >>= PAGE_SHIFT; + if (lock_limit != RLIM_INFINITY) + lock_limit >>= PAGE_SHIFT; spin_lock(&shmlock_user_lock); memlock = inc_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked); - if (!allowed && (memlock == LONG_MAX || memlock > lock_limit) && !capable(CAP_IPC_LOCK)) { + if ((memlock == LONG_MAX || memlock > lock_limit) && !capable(CAP_IPC_LOCK)) { dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked); goto out; } -- cgit v1.2.3