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Tejun Heo 0196bdf590 cgroup: fix css_task_iter crash on CSS_TASK_ITER_PROC 
commit 74d0833c65 upstream.

While teaching css_task_iter to handle skipping over tasks which
aren't group leaders, bc2fb7ed08 ("cgroup: add @flags to
css_task_iter_start() and implement CSS_TASK_ITER_PROCS") introduced a
silly bug.

CSS_TASK_ITER_PROCS is implemented by repeating
css_task_iter_advance() while the advanced cursor is pointing to a
non-leader thread.  However, the cursor variable, @l, wasn't updated
when the iteration has to advance to the next css_set and the
following repetition would operate on the terminal @l from the
previous iteration which isn't pointing to a valid task leading to
oopses like the following or infinite looping.

  BUG: unable to handle kernel NULL pointer dereference at 0000000000000254
  IP: __task_pid_nr_ns+0xc7/0xf0
  PGD 0 P4D 0
  Oops: 0000 [#1] SMP
  ...
  CPU: 2 PID: 1 Comm: systemd Not tainted 4.14.4-200.fc26.x86_64 #1
  Hardware name: System manufacturer System Product Name/PRIME B350M-A, BIOS 3203 11/09/2017
  task: ffff88c4baee8000 task.stack: ffff96d5c3158000
  RIP: 0010:__task_pid_nr_ns+0xc7/0xf0
  RSP: 0018:ffff96d5c315bd50 EFLAGS: 00010206
  RAX: 0000000000000000 RBX: ffff88c4b68c6000 RCX: 0000000000000250
  RDX: ffffffffa5e47960 RSI: 0000000000000000 RDI: ffff88c490f6ab00
  RBP: ffff96d5c315bd50 R08: 0000000000001000 R09: 0000000000000005
  R10: ffff88c4be006b80 R11: ffff88c42f1b8004 R12: ffff96d5c315bf18
  R13: ffff88c42d7dd200 R14: ffff88c490f6a510 R15: ffff88c4b68c6000
  FS:  00007f9446f8ea00(0000) GS:ffff88c4be680000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: 0000000000000254 CR3: 00000007f956f000 CR4: 00000000003406e0
  Call Trace:
   cgroup_procs_show+0x19/0x30
   cgroup_seqfile_show+0x4c/0xb0
   kernfs_seq_show+0x21/0x30
   seq_read+0x2ec/0x3f0
   kernfs_fop_read+0x134/0x180
   __vfs_read+0x37/0x160
   ? security_file_permission+0x9b/0xc0
   vfs_read+0x8e/0x130
   SyS_read+0x55/0xc0
   entry_SYSCALL_64_fastpath+0x1a/0xa5
  RIP: 0033:0x7f94455f942d
  RSP: 002b:00007ffe81ba2d00 EFLAGS: 00000293 ORIG_RAX: 0000000000000000
  RAX: ffffffffffffffda RBX: 00005574e2233f00 RCX: 00007f94455f942d
  RDX: 0000000000001000 RSI: 00005574e2321a90 RDI: 000000000000002b
  RBP: 0000000000000000 R08: 00005574e2321a90 R09: 00005574e231de60
  R10: 00007f94458c8b38 R11: 0000000000000293 R12: 00007f94458c8ae0
  R13: 00007ffe81ba3800 R14: 0000000000000000 R15: 00005574e2116560
  Code: 04 74 0e 89 f6 48 8d 04 76 48 8d 04 c5 f0 05 00 00 48 8b bf b8 05 00 00 48 01 c7 31 c0 48 8b 0f 48 85 c9 74 18 8b b2 30 08 00 00 <3b> 71 04 77 0d 48 c1 e6 05 48 01 f1 48 3b 51 38 74 09 5d c3 8b
  RIP: __task_pid_nr_ns+0xc7/0xf0 RSP: ffff96d5c315bd50

Fix it by moving the initialization of the cursor below the repeat
label.  While at it, rename it to @next for readability.

Signed-off-by: Tejun Heo <tj@kernel.org>
Fixes: bc2fb7ed08 ("cgroup: add @flags to css_task_iter_start() and implement CSS_TASK_ITER_PROCS")
Reported-by: Laura Abbott <labbott@redhat.com>
Reported-by: Bronek Kozicki <brok@incorrekt.com>
Reported-by: George Amanakis <gamanakis@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2018-01-17 09:45:18 +01:00
arch MIPS: Disallow outsized PTRACE_SETREGSET NT_PRFPREG regset accesses 2018-01-17 09:45:18 +01:00
block block: don't let passthrough IO go into .make_request_fn() 2018-01-02 20:31:05 +01:00
certs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crypto crypto: pcrypt - fix freeing pcrypt instances 2018-01-10 09:31:18 +01:00
Documentation x86/kaslr: Fix the vaddr_end mess 2018-01-10 09:31:16 +01:00
drivers IB/srpt: Fix ACL lookup during login 2018-01-17 09:45:17 +01:00
firmware License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fs x86 / CPU: Always show current CPU frequency in /proc/cpuinfo 2018-01-10 09:31:20 +01:00
include KVM: Fix stack-out-of-bounds read in write_mmio 2018-01-17 09:45:17 +01:00
init x86/mm/pti: Add infrastructure for page table isolation 2018-01-02 20:30:56 +01:00
ipc License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
kernel cgroup: fix css_task_iter crash on CSS_TASK_ITER_PROC 2018-01-17 09:45:18 +01:00
lib x86/unwind: Rename unwinder config options to 'CONFIG_UNWINDER_*' 2017-12-25 14:26:13 +01:00
mm mm/sparse.c: wrong allocation for mem_section 2018-01-10 09:31:17 +01:00
net Revert "xfrm: Fix stack-out-of-bounds read in xfrm_state_find." 2018-01-05 15:48:58 +01:00
samples samples/bpf: adjust rlimit RLIMIT_MEMLOCK for xdp1 2017-12-20 10:10:31 +01:00
scripts linux/compiler.h: Split into compiler.h and compiler_types.h 2017-12-25 14:26:33 +01:00
security apparmor: fix regression in mount mediation when feature set is pinned 2018-01-10 09:31:22 +01:00
sound ALSA: hda - Fix missing COEF init for ALC225/295/299 2018-01-02 20:31:05 +01:00
tools usbip: fix usbip bind writing random string after command in match_busid 2018-01-02 20:31:13 +01:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt KVM: Fix stack-out-of-bounds read in write_mmio 2018-01-17 09:45:17 +01:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support to generate LLVM assembly files 2017-04-25 08:13:52 +09:00
.mailmap .mailmap: Add Maciej W. Rozycki's Imagination e-mail address 2017-11-10 12:16:15 -08:00
COPYING [PATCH] update FSF address in COPYING 2005-09-10 10:06:29 -07:00
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS Merge branch 'akpm' (patches from Andrew) 2017-11-09 18:26:51 -08:00
Makefile Linux 4.14.13 2018-01-10 09:31:23 +01:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

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.