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Ravi Bangoria ba16293dad tracing: Fix kernel crash while using empty filter with perf 
Kernel is crashing when user tries to record 'ftrace:function' event
with empty filter:

  # perf record -e ftrace:function --filter="" ls

  # dmesg
  BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
  Oops: 0000 [#1] SMP PTI
  ...
  RIP: 0010:ftrace_profile_set_filter+0x14b/0x2d0
  RSP: 0018:ffffa4a7c0da7d20 EFLAGS: 00010246
  RAX: ffffa4a7c0da7d64 RBX: 0000000000000000 RCX: 0000000000000006
  RDX: 0000000000000000 RSI: 0000000000000092 RDI: ffff8c48ffc968f0
  ...
  Call Trace:
   _perf_ioctl+0x54a/0x6b0
   ? rcu_all_qs+0x5/0x30
  ...

After patch:
  # perf record -e ftrace:function --filter="" ls
  failed to set filter "" on event ftrace:function with 22 (Invalid argument)

Also, if user tries to echo "" > filter, it used to throw an error.
This behavior got changed by commit 80765597bc ("tracing: Rewrite
filter logic to be simpler and faster"). This patch restores the
behavior as a side effect:

Before patch:
  # echo "" > filter
  #

After patch:
  # echo "" > filter
  bash: echo: write error: Invalid argument
  #

Link: http://lkml.kernel.org/r/20180420150758.19787-1-ravi.bangoria@linux.ibm.com

Fixes: 80765597bc ("tracing: Rewrite filter logic to be simpler and faster")
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
2018-04-25 10:27:55 -04:00
arch tracing/x86: Update syscall trace events to handle new prefixed syscall func names 2018-04-25 10:27:55 -04:00
block blk-mq: Revert "blk-mq: reimplement blk_mq_hw_queue_mapped" 2018-04-11 07:59:15 -06:00
certs certs/blacklist_nohashes.c: fix const confusion in certs blacklist 2018-02-21 15:35:43 -08:00
crypto Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
Documentation Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-04-15 16:12:35 -07:00
drivers SCSI fixes on 20180415 2018-04-15 17:24:12 -07:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs for-4.17-part2-tag 2018-04-15 18:08:35 -07:00
include tracing: Add missing forward declaration 2018-04-19 11:05:48 -04:00
init Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-04-15 16:12:35 -07:00
ipc ipc/shm: fix use-after-free of shm file via remap_file_pages() 2018-04-13 17:10:27 -07:00
kernel tracing: Fix kernel crash while using empty filter with perf 2018-04-25 10:27:55 -04:00
lib Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-04-15 16:12:35 -07:00
LICENSES LICENSES: Add MPL-1.1 license 2018-01-06 10:59:44 -07:00
mm mm, slab: reschedule cache_reap() on the same CPU 2018-04-13 17:10:27 -07:00
net Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
samples remoteproc updates for v4.17 2018-04-10 12:09:27 -07:00
scripts Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
security + Features 2018-04-13 15:38:53 -07:00
sound amdgpu, omap and snd regression fix 2018-04-12 20:56:10 -07:00
tools Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
usr kbuild: rename built-in.o to built-in.a 2018-03-26 02:01:19 +09:00
virt KVM/ARM updates for v4.17 2018-03-28 16:09:09 +02:00
.clang-format clang-format: add configuration file 2018-04-11 10:28:35 -07:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap Merge candidates for 4.17 merge window 2018-04-06 17:35:43 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS/CREDITS: Drop METAG ARCHITECTURE 2018-03-05 16:34:24 +00:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS Changes to chrome-platform for v4.17 2018-04-13 16:20:36 -07:00
Makefile Linux 4.17-rc1 2018-04-15 18:24:20 -07:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

README 

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

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

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.