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Filename Latest commit message Latest commit date
Peter Zijlstra 8b405d5c5d locking/lockdep: Fix stacktrace mess
There is some complication between check_prevs_add() and
check_prev_add() wrt. saving stack traces. The problem is that we want
to be frugal with saving stack traces, since it consumes static
resources.

We'll only know in check_prev_add() if we need the trace, but we can
call into it multiple times. So we want to do on-demand and re-use.

A further complication is that check_prev_add() can drop graph_lock
and mess with our static resources.

In any case, the current state; after commit:

  ce07a9415f ("locking/lockdep: Make check_prev_add() able to handle external stack_trace")

is that we'll assume the trace contains valid data once
check_prev_add() returns '2'. However, as noted by Josh, this is
false, check_prev_add() can return '2' before having saved a trace,
this then result in the possibility of using uninitialized data.
Testing, as reported by Wu, shows a NULL deref.

So simplify.

Since the graph_lock() thing is a debug path that hasn't
really been used in a long while, take it out back and avoid the
head-ache.

Further initialize the stack_trace to a known 'empty' state; as long
as nr_entries == 0, nothing should deref entries. We can then use the
'entries == NULL' test for a valid trace / on-demand saving.

Analyzed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: ce07a9415f ("locking/lockdep: Make check_prev_add() able to handle external stack_trace")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-10-10 10:04:28 +02:00
arch Merge branch 'ppc-bundle' (bundle from Michael Ellerman) 2017-10-09 19:08:32 -07:00
block bsg-lib: fix use-after-free under memory-pressure 2017-10-04 08:35:04 -06:00
certs
crypto
Documentation Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-10-09 16:25:00 -07:00
drivers Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-10-09 16:25:00 -07:00
firmware
fs NFS client bugfixes for Linux 4.14 2017-10-09 10:55:37 -07:00
include Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-10-09 16:25:00 -07:00
init
ipc fix a typo in put_compat_shm_info() 2017-09-25 20:41:46 -04:00
kernel locking/lockdep: Fix stacktrace mess 2017-10-10 10:04:28 +02:00
lib lib/ratelimit.c: use deferred printk() version 2017-10-03 17:54:26 -07:00
mm mm/memory_hotplug: define find_{smallest|biggest}_section_pfn as unsigned long 2017-10-03 17:54:26 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-10-09 16:25:00 -07:00
samples
scripts checkpatch: fix ignoring cover-letter logic 2017-10-03 17:54:26 -07:00
security lsm: fix smack_inode_removexattr and xattr_getsecurity memleak 2017-10-04 18:03:15 +11:00
sound sound fixes for 4.14-rc4 2017-10-05 10:39:29 -07:00
tools selftests/net: rxtimestamp: Fix an off by one 2017-10-05 21:28:53 -07:00
usr
virt
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap Update James Hogan's email address 2017-10-04 17:11:53 -07:00
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS ARC udpates for 4.14-rc4 2017-10-06 15:57:08 -07:00
Makefile Linux 4.14-rc4 2017-10-08 20:53:29 -07:00
README

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.