Bug 203123

Summary:	MPX is broken
Product:	Platform Specific/Hardware	Reporter:	H.J. Lu (hjl.tools)
Component:	x86-64	Assignee:	platform_x86_64 (platform_x86_64)
Status:	RESOLVED OBSOLETE
Severity:	normal	CC:	dave
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	4.20	Subsystem:
Regression:	No	Bisected commit-id:

Description H.J. Lu 2019-04-01 13:26:03 UTC

On machines with MPX, gcc/testsuite/gcc.target/i386/mpx/memmove-1.c
from GCC 8 failed under kernel 4.20:

[hjl@gnu-skl-1 tmp]$ gcc -fcheck-pointer-bounds -mmpx /export/gnu/import/git/sources/gcc-release/gcc/testsuite/gcc.target/i386/mpx/memmove-1.c
[hjl@gnu-skl-1 tmp]$ ./a.out 
Segmentation fault
[hjl@gnu-skl-1 tmp]$ 

[   75.636402] BUG: Bad rss-counter state mm:000000002cc54919 idx:0 val:328
[   75.636431] BUG: Bad rss-counter state mm:000000002cc54919 idx:1 val:28
[   75.636453] BUG: non-zero pgtables_bytes on freeing mm: 24576

Comment 1 Dave Hansen 2019-04-01 14:41:58 UTC

Here's a fix:

http://lkml.kernel.org/r/20190401141549.3F4721FE@viggo.jf.intel.com

Testing would be appreciated.

Comment 2 H.J. Lu 2019-04-01 18:40:35 UTC

This is triggered by

commit dd2283f2605e3b3e9c61bcae844b34f2afa4813f
Author: Yang Shi <yang.shi@linux.alibaba.com>
Date:   Fri Oct 26 15:07:11 2018 -0700

    mm: mmap: zap pages with read mmap_sem in munmap

Comment 3 H.J. Lu 2019-04-01 18:40:59 UTC

(In reply to Dave Hansen from comment #1)
> Here's a fix:
> 
> http://lkml.kernel.org/r/20190401141549.3F4721FE@viggo.jf.intel.com
> 
> Testing would be appreciated.

Yes, it did fix the problem.

Comment 4 H.J. Lu 2020-09-05 16:34:44 UTC

MPX has been deprecated.