linux-kernel - [GIT PULL] locking fixes

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Date:   Sat, 18 Jan 2020 18:53:09 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [GIT PULL] locking fixes

Linus,

Please pull the latest locking-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking-urgent-for-linus

   # HEAD: 39e7234f00bc93613c086ae42d852d5f4147120a locking/rwsem: Fix kernel crash when spinning on RWSEM_OWNER_UNKNOWN

Three fixes:

 - Fix an rwsem spin-on-owner crash, introduced in v5.4
 - Fix a lockdep bug when running out of stack_trace entries, introduced in v5.4
 - Docbook fix

 Thanks,

	Ingo

------------------>
Randy Dunlap (1):
      futex: Fix kernel-doc notation warning

Waiman Long (2):
      locking/lockdep: Fix buffer overrun problem in stack_trace[]
      locking/rwsem: Fix kernel crash when spinning on RWSEM_OWNER_UNKNOWN


 kernel/futex.c           | 1 +
 kernel/locking/lockdep.c | 7 +++----
 kernel/locking/rwsem.c   | 4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 03c518e9747e..0cf84c8664f2 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1178,6 +1178,7 @@ static int attach_to_pi_state(u32 __user *uaddr, u32 uval,
 
 /**
  * wait_for_owner_exiting - Block until the owner has exited
+ * @ret: owner's current futex lock status
  * @exiting:	Pointer to the exiting task
  *
  * Caller must hold a refcount on @exiting.
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 32282e7112d3..32406ef0d6a2 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -482,7 +482,7 @@ static struct lock_trace *save_trace(void)
 	struct lock_trace *trace, *t2;
 	struct hlist_head *hash_head;
 	u32 hash;
-	unsigned int max_entries;
+	int max_entries;
 
 	BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
 	BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
@@ -490,10 +490,8 @@ static struct lock_trace *save_trace(void)
 	trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
 	max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
 		LOCK_TRACE_SIZE_IN_LONGS;
-	trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
 
-	if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES -
-	    LOCK_TRACE_SIZE_IN_LONGS - 1) {
+	if (max_entries <= 0) {
 		if (!debug_locks_off_graph_unlock())
 			return NULL;
 
@@ -502,6 +500,7 @@ static struct lock_trace *save_trace(void)
 
 		return NULL;
 	}
+	trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
 
 	hash = jhash(trace->entries, trace->nr_entries *
 		     sizeof(trace->entries[0]), 0);
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 44e68761f432..0d9b6be9ecc8 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -1226,8 +1226,8 @@ rwsem_down_write_slowpath(struct rw_semaphore *sem, int state)
 		 * In this case, we attempt to acquire the lock again
 		 * without sleeping.
 		 */
-		if ((wstate == WRITER_HANDOFF) &&
-		    (rwsem_spin_on_owner(sem, 0) == OWNER_NULL))
+		if (wstate == WRITER_HANDOFF &&
+		    rwsem_spin_on_owner(sem, RWSEM_NONSPINNABLE) == OWNER_NULL)
 			goto trylock_again;
 
 		/* Block until there are no active lockers. */