- Make sure the switch to the global hash is requested always under a lock so

that two threads requesting that simultaneously cannot get to inconsistent
   state
 
 - Reject negative NUMA nodes earlier in the futex NUMA interface handling code
 
 - Selftests fixes
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Merge tag 'locking_urgent_for_v6.16_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull locking fixes from Borislav Petkov:

 - Make sure the switch to the global hash is requested always under a
   lock so that two threads requesting that simultaneously cannot get to
   inconsistent state

 - Reject negative NUMA nodes earlier in the futex NUMA interface
   handling code

 - Selftests fixes

* tag 'locking_urgent_for_v6.16_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  futex: Verify under the lock if hash can be replaced
  futex: Handle invalid node numbers supplied by user
  selftests/futex: Set the home_node in futex_numa_mpol
  selftests/futex: getopt() requires int as return value.

kernel/futex/core.c

@@ -583,8 +583,8 @@ int get_futex_key(u32 __user *uaddr, unsigned int flags, union futex_key *key,
 		if (futex_get_value(&node, naddr))
 			return -EFAULT;
 
-		if (node != FUTEX_NO_NODE &&
-		    (node >= MAX_NUMNODES || !node_possible(node)))
+		if ((node != FUTEX_NO_NODE) &&
+		    ((unsigned int)node >= MAX_NUMNODES || !node_possible(node)))
 			return -EINVAL;
 	}
 
@@ -1629,6 +1629,16 @@ again:
 		mm->futex_phash_new = NULL;
 
 		if (fph) {
+			if (cur && (!cur->hash_mask || cur->immutable)) {
+				/*
+				 * If two threads simultaneously request the global
+				 * hash then the first one performs the switch,
+				 * the second one returns here.
+				 */
+				free = fph;
+				mm->futex_phash_new = new;
+				return -EBUSY;
+			}
 			if (cur && !new) {
 				/*
 				 * If we have an existing hash, but do not yet have

tools/testing/selftests/futex/functional/futex_numa_mpol.c

@@ -144,7 +144,7 @@ int main(int argc, char *argv[])
 	struct futex32_numa *futex_numa;
 	int mem_size, i;
 	void *futex_ptr;
-	char c;
+	int c;
 
 	while ((c = getopt(argc, argv, "chv:")) != -1) {
 		switch (c) {
@@ -210,6 +210,10 @@ int main(int argc, char *argv[])
 		ret = mbind(futex_ptr, mem_size, MPOL_BIND, &nodemask,
 			    sizeof(nodemask) * 8, 0);
 		if (ret == 0) {
+			ret = numa_set_mempolicy_home_node(futex_ptr, mem_size, i, 0);
+			if (ret != 0)
+				ksft_exit_fail_msg("Failed to set home node: %m, %d\n", errno);
+
 			ksft_print_msg("Node %d test\n", i);
 			futex_numa->futex = 0;
 			futex_numa->numa = FUTEX_NO_NODE;
@@ -220,8 +224,8 @@ int main(int argc, char *argv[])
 			if (0)
 				test_futex_mpol(futex_numa, 0);
 			if (futex_numa->numa != i) {
-				ksft_test_result_fail("Returned NUMA node is %d expected %d\n",
-						      futex_numa->numa, i);
+				ksft_exit_fail_msg("Returned NUMA node is %d expected %d\n",
+						   futex_numa->numa, i);
 			}
 		}
 	}

tools/testing/selftests/futex/functional/futex_priv_hash.c

@@ -130,7 +130,7 @@ int main(int argc, char *argv[])
 	pthread_mutexattr_t mutex_attr_pi;
 	int use_global_hash = 0;
 	int ret;
-	char c;
+	int c;
 
 	while ((c = getopt(argc, argv, "cghv:")) != -1) {
 		switch (c) {