ucounts: Fix shm ucounts

The introduction of a new failure mode when the code was converted to
 ucounts resulted in user_shm_lock misbehaving.  The change simplifies
 the code to make the code easier to follow and remove the known
 misbehaviors.
 
 Miaohe Lin (1):
       mm/mlock: fix two bugs in user_shm_lock()
 
  mm/mlock.c | 7 +++----
  1 file changed, 3 insertions(+), 4 deletions(-)
 
 Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Merge tag 'ucount-rlimit-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

Pull shm ucounts fix from Eric Biederman:
 "The introduction of a new failure mode when the code was converted to
  ucounts resulted in user_shm_lock misbehaving.

  The change simplifies the code to make the code easier to follow and
  removes the known misbehaviors"

* tag 'ucount-rlimit-for-v5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  mm/mlock: fix two bugs in user_shm_lock()

mm/mlock.c

@@ -721,13 +721,12 @@ 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)
+	if (lock_limit != RLIM_INFINITY)
-		allowed = 1;
+		lock_limit >>= PAGE_SHIFT;
-	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;
 	}