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| author | Miaohe Lin <linmiaohe@huawei.com> | 2022-03-22 09:09:18 +0100 |
|---|---|---|
| committer | Eric W. Biederman <ebiederm@xmission.com> | 2022-03-23 17:16:59 +0100 |
| commit | e97824ff663ce3509fe040431c713182c2f058b1 (patch) | |
| tree | e034a0a6eddcd8b5654efbe3f744949e73e2ff47 /mm | |
| parent | Linux 5.17-rc7 (diff) | |
| download | linux-e97824ff663ce3509fe040431c713182c2f058b1.tar.xz linux-e97824ff663ce3509fe040431c713182c2f058b1.zip | |
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 <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>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/mlock.c | 7 |
1 files changed, 3 insertions, 4 deletions
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; } |