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Laura Abbott 1b7e816fc8 mm: slub: Fix slab walking for init_on_free
To properly clear the slab on free with slab_want_init_on_free, we walk
the list of free objects using get_freepointer/set_freepointer.

The value we get from get_freepointer may not be valid.  This isn't an
issue since an actual value will get written later but this means
there's a chance of triggering a bug if we use this value with
set_freepointer:

  kernel BUG at mm/slub.c:306!
  invalid opcode: 0000 [#1] PREEMPT PTI
  CPU: 0 PID: 0 Comm: swapper Not tainted 5.2.0-05754-g6471384a #4
  RIP: 0010:kfree+0x58a/0x5c0
  Code: 48 83 05 78 37 51 02 01 0f 0b 48 83 05 7e 37 51 02 01 48 83 05 7e 37 51 02 01 48 83 05 7e 37 51 02 01 48 83 05 d6 37 51 02 01 <0f> 0b 48 83 05 d4 37 51 02 01 48 83 05 d4 37 51 02 01 48 83 05 d4
  RSP: 0000:ffffffff82603d90 EFLAGS: 00010002
  RAX: ffff8c3976c04320 RBX: ffff8c3976c04300 RCX: 0000000000000000
  RDX: ffff8c3976c04300 RSI: 0000000000000000 RDI: ffff8c3976c04320
  RBP: ffffffff82603db8 R08: 0000000000000000 R09: 0000000000000000
  R10: ffff8c3976c04320 R11: ffffffff8289e1e0 R12: ffffd52cc8db0100
  R13: ffff8c3976c01a00 R14: ffffffff810f10d4 R15: ffff8c3976c04300
  FS:  0000000000000000(0000) GS:ffffffff8266b000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  CR2: ffff8c397ffff000 CR3: 0000000125020000 CR4: 00000000000406b0
  Call Trace:
   apply_wqattrs_prepare+0x154/0x280
   apply_workqueue_attrs_locked+0x4e/0xe0
   apply_workqueue_attrs+0x36/0x60
   alloc_workqueue+0x25a/0x6d0
   workqueue_init_early+0x246/0x348
   start_kernel+0x3c7/0x7ec
   x86_64_start_reservations+0x40/0x49
   x86_64_start_kernel+0xda/0xe4
   secondary_startup_64+0xb6/0xc0
  Modules linked in:
  ---[ end trace f67eb9af4d8d492b ]---

Fix this by ensuring the value we set with set_freepointer is either NULL
or another value in the chain.

Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: Laura Abbott <labbott@redhat.com>
Fixes: 6471384af2 ("mm: security: introduce init_on_alloc=1 and init_on_free=1 boot options")
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-31 13:16:06 -07:00
Documentation HMM patches for 5.3-rc 2019-07-30 12:54:44 -07:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch SPDX fixes for 5.3-rc2 2019-07-28 10:00:06 -07:00
block for-linus-20190726-2 2019-07-26 19:20:34 -07:00
certs Revert "Merge tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs" 2019-07-10 18:43:43 -07:00
crypto USB / PHY patches for 5.3-rc1 2019-07-11 15:40:06 -07:00
drivers One necessary fix for an uninitialized variable in the new IPMB driver. 2019-07-31 10:13:00 -07:00
fs Merge branch 'dax-fix-5.3-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm 2019-07-30 17:32:46 -07:00
include Two minor fixes: 2019-07-31 10:26:59 -07:00
init Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
ipc Merge branch 'work.mount0' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-07-19 10:42:02 -07:00
kernel Two minor fixes: 2019-07-31 10:26:59 -07:00
lib test_firmware: fix a memory leak bug 2019-07-25 14:39:52 +02:00
mm mm: slub: Fix slab walking for init_on_free 2019-07-31 13:16:06 -07:00
net tcp: be more careful in tcp_fragment() 2019-07-21 20:41:24 -07:00
samples treewide: remove SPDX "WITH Linux-syscall-note" from kernel-space headers again 2019-07-25 11:05:10 +02:00
scripts Kbuild fixes for v5.3 2019-07-28 10:35:04 -07:00
security meminit fix 2019-07-28 12:33:15 -07:00
sound sound fixes for 5.3-rc2 2019-07-26 10:23:45 -07:00
tools for-linus-20190730 2019-07-30 13:25:14 -07:00
usr kbuild: enable arch/s390/include/uapi/asm/zcrypt.h for uapi header test 2019-07-23 10:45:46 +02:00
virt Documentation: move Documentation/virtual to Documentation/virt 2019-07-24 10:52:11 +02:00
.clang-format Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-17 11:26:25 -07:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore .gitignore: Add compilation database file 2019-07-27 12:18:19 +09:00
.mailmap MAINTAINERS: Update my email address 2019-07-22 14:57:50 +01:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Remove references to dead website. 2019-07-19 12:22:04 -07:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Char/Misc driver fixes for 5.3-rc2 2019-07-28 10:26:10 -07:00
Makefile Linux 5.3-rc2 2019-07-28 12:47:02 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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.

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.