Patch "tools/lib/lockdep: Reduce MAX_LOCK_DEPTH to avoid overflowing lock_chain/: Depth" has been added to the 4.12-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    tools/lib/lockdep: Reduce MAX_LOCK_DEPTH to avoid overflowing lock_chain/: Depth

to the 4.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tools-lib-lockdep-reduce-max_lock_depth-to-avoid-overflowing-lock_chain-depth.patch
and it can be found in the queue-4.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 98dcea0cfd04e083ac74137ceb9a632604740e2d Mon Sep 17 00:00:00 2001
From: Ben Hutchings <ben@decadent.org.uk>
Date: Thu, 25 May 2017 12:58:33 +0000
Subject: tools/lib/lockdep: Reduce MAX_LOCK_DEPTH to avoid overflowing lock_chain/: Depth

From: Ben Hutchings <ben@decadent.org.uk>

commit 98dcea0cfd04e083ac74137ceb9a632604740e2d upstream.

liblockdep has been broken since commit 75dd602a5198 ("lockdep: Fix
lock_chain::base size"), as that adds a check that MAX_LOCK_DEPTH is
within the range of lock_chain::depth and in liblockdep it is much
too large.

That should have resulted in a compiler error, but didn't because:

- the check uses ARRAY_SIZE(), which isn't yet defined in liblockdep
  so is assumed to be an (undeclared) function
- putting a function call inside a BUILD_BUG_ON() expression quietly
  turns it into some nonsense involving a variable-length array

It did produce a compiler warning, but I didn't notice because
liblockdep already produces too many warnings if -Wall is enabled
(which I'll fix shortly).

Even before that commit, which reduced lock_chain::depth from 8 bits
to 6, MAX_LOCK_DEPTH was too large.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: a.p.zijlstra@chello.nl
Link: http://lkml.kernel.org/r/20170525130005.5947-3-alexander.levin@verizon.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 tools/lib/lockdep/uinclude/linux/lockdep.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/tools/lib/lockdep/uinclude/linux/lockdep.h
+++ b/tools/lib/lockdep/uinclude/linux/lockdep.h
@@ -8,7 +8,7 @@
 #include <linux/utsname.h>
 #include <linux/compiler.h>
 
-#define MAX_LOCK_DEPTH 2000UL
+#define MAX_LOCK_DEPTH 63UL
 
 #define asmlinkage
 #define __visible


Patches currently in stable-queue which might be from ben@decadent.org.uk are

queue-4.12/tools-lib-lockdep-reduce-max_lock_depth-to-avoid-overflowing-lock_chain-depth.patch