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Krzysztof Kozlowski ba2539b5f9 nfc: llcp: fix NULL error pointer dereference on sendmsg() after failed bind() 
commit dded08927c upstream.

Syzbot detected a NULL pointer dereference of nfc_llcp_sock->dev pointer
(which is a 'struct nfc_dev *') with calls to llcp_sock_sendmsg() after
a failed llcp_sock_bind(). The message being sent is a SOCK_DGRAM.

KASAN report:

  BUG: KASAN: null-ptr-deref in nfc_alloc_send_skb+0x2d/0xc0
  Read of size 4 at addr 00000000000005c8 by task llcp_sock_nfc_a/899

  CPU: 5 PID: 899 Comm: llcp_sock_nfc_a Not tainted 5.16.0-rc6-next-20211224-00001-gc6437fbf18b0 #125
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
  Call Trace:
   <TASK>
   dump_stack_lvl+0x45/0x59
   ? nfc_alloc_send_skb+0x2d/0xc0
   __kasan_report.cold+0x117/0x11c
   ? mark_lock+0x480/0x4f0
   ? nfc_alloc_send_skb+0x2d/0xc0
   kasan_report+0x38/0x50
   nfc_alloc_send_skb+0x2d/0xc0
   nfc_llcp_send_ui_frame+0x18c/0x2a0
   ? nfc_llcp_send_i_frame+0x230/0x230
   ? __local_bh_enable_ip+0x86/0xe0
   ? llcp_sock_connect+0x470/0x470
   ? llcp_sock_connect+0x470/0x470
   sock_sendmsg+0x8e/0xa0
   ____sys_sendmsg+0x253/0x3f0
   ...

The issue was visible only with multiple simultaneous calls to bind() and
sendmsg(), which resulted in most of the bind() calls to fail.  The
bind() was failing on checking if there is available WKS/SDP/SAP
(respective bit in 'struct nfc_llcp_local' fields).  When there was no
available WKS/SDP/SAP, the bind returned error but the sendmsg() to such
socket was able to trigger mentioned NULL pointer dereference of
nfc_llcp_sock->dev.

The code looks simply racy and currently it protects several paths
against race with checks for (!nfc_llcp_sock->local) which is NULL-ified
in error paths of bind().  The llcp_sock_sendmsg() did not have such
check but called function nfc_llcp_send_ui_frame() had, although not
protected with lock_sock().

Therefore the race could look like (same socket is used all the time):
  CPU0                                     CPU1
  ====                                     ====
  llcp_sock_bind()
  - lock_sock()
    - success
  - release_sock()
  - return 0
                                           llcp_sock_sendmsg()
                                           - lock_sock()
                                           - release_sock()
  llcp_sock_bind(), same socket
  - lock_sock()
    - error
                                           - nfc_llcp_send_ui_frame()
                                             - if (!llcp_sock->local)
    - llcp_sock->local = NULL
    - nfc_put_device(dev)
                                             - dereference llcp_sock->dev
  - release_sock()
  - return -ERRNO

The nfc_llcp_send_ui_frame() checked llcp_sock->local outside of the
lock, which is racy and ineffective check.  Instead, its caller
llcp_sock_sendmsg(), should perform the check inside lock_sock().

Reported-and-tested-by: syzbot+7f23bcddf626e0593a39@syzkaller.appspotmail.com
Fixes: b874dec21d ("NFC: Implement LLCP connection less Tx path")
Cc: <stable@vger.kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-01-27 09:19:26 +01:00
arch ARM: 9025/1: Kconfig: CPU_BIG_ENDIAN depends on !LD_IS_LLD 2022-01-20 09:19:19 +01:00
block block: fix ioprio_get(IOPRIO_WHO_PGRP) vs setuid(2) 2021-12-14 14:49:02 +01:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2021-09-15 09:47:29 +02:00
crypto crypto: pcrypt - Delay write to padata->info 2021-11-17 09:48:40 +01:00
Documentation Input: i8042 - add deferred probe support 2022-01-05 12:37:43 +01:00
drivers HID: wacom: Avoid using stale array indicies to read contact count 2022-01-27 09:19:26 +01:00
fs f2fs: fix to do sanity check in is_alive() 2022-01-27 09:19:26 +01:00
include perf: Protect perf_guest_cbs with RCU 2022-01-20 09:19:18 +01:00
init kbuild: add CONFIG_LD_IS_LLD 2021-06-30 08:47:44 -04:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-12-01 09:23:35 +01:00
kernel perf: Protect perf_guest_cbs with RCU 2022-01-20 09:19:18 +01:00
lib siphash: use _unaligned version by default 2021-12-08 09:01:12 +01:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm: mempolicy: fix THP allocations escaping mempolicy restrictions 2021-12-29 12:23:37 +01:00
net nfc: llcp: fix NULL error pointer dereference on sendmsg() after failed bind() 2022-01-27 09:19:26 +01:00
samples samples/kretprobes: Fix return value if register_kretprobe() failed 2021-11-17 09:48:39 +01:00
scripts recordmcount.pl: fix typo in s390 mcount regex 2022-01-05 12:37:44 +01:00
security selinux: initialize proto variable in selinux_ip_postroute_compat() 2022-01-05 12:37:44 +01:00
sound ALSA: hda/realtek - Fix silent output on Gigabyte X570 Aorus Master after reboot from Windows 2022-01-20 09:19:18 +01:00
tools selftests: x86: fix [-Wstringop-overread] warn in test_process_vm_readv() 2022-01-11 15:23:31 +01:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: do not shrink halt_poll_ns below grow_start 2021-10-09 14:39:50 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.173 2022-01-20 09:19:19 +01:00
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.