patches/kernel/0011-net-crypto-set-sk-to-NULL-when-af_alg_release.patch

   1 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
   2 From: Mao Wenan <maowenan@huawei.com>
   3 Date: Mon, 18 Feb 2019 10:44:44 +0800
   4 Subject: [PATCH] net: crypto set sk to NULL when af_alg_release.
   5
   6 KASAN has found use-after-free in sockfs_setattr.
   7 The existed commit 6d8c50dcb029 ("socket: close race condition between sock_close()
   8 and sockfs_setattr()") is to fix this simillar issue, but it seems to ignore
   9 that crypto module forgets to set the sk to NULL after af_alg_release.
  10
  11 KASAN report details as below:
  12 BUG: KASAN: use-after-free in sockfs_setattr+0x120/0x150
  13 Write of size 4 at addr ffff88837b956128 by task syz-executor0/4186
  14
  15 CPU: 2 PID: 4186 Comm: syz-executor0 Not tainted xxx + #1
  16 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
  17 1.10.2-1ubuntu1 04/01/2014
  18 Call Trace:
  19  dump_stack+0xca/0x13e
  20  print_address_description+0x79/0x330
  21  ? vprintk_func+0x5e/0xf0
  22  kasan_report+0x18a/0x2e0
  23  ? sockfs_setattr+0x120/0x150
  24  sockfs_setattr+0x120/0x150
  25  ? sock_register+0x2d0/0x2d0
  26  notify_change+0x90c/0xd40
  27  ? chown_common+0x2ef/0x510
  28  chown_common+0x2ef/0x510
  29  ? chmod_common+0x3b0/0x3b0
  30  ? __lock_is_held+0xbc/0x160
  31  ? __sb_start_write+0x13d/0x2b0
  32  ? __mnt_want_write+0x19a/0x250
  33  do_fchownat+0x15c/0x190
  34  ? __ia32_sys_chmod+0x80/0x80
  35  ? trace_hardirqs_on_thunk+0x1a/0x1c
  36  __x64_sys_fchownat+0xbf/0x160
  37  ? lockdep_hardirqs_on+0x39a/0x5e0
  38  do_syscall_64+0xc8/0x580
  39  entry_SYSCALL_64_after_hwframe+0x49/0xbe
  40 RIP: 0033:0x462589
  41 Code: f7 d8 64 89 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 48 89 f8 48 89
  42 f7 48 89 d6 48 89
  43 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3
  44 48 c7 c1 bc ff ff
  45 ff f7 d8 64 89 01 48
  46 RSP: 002b:00007fb4b2c83c58 EFLAGS: 00000246 ORIG_RAX: 0000000000000104
  47 RAX: ffffffffffffffda RBX: 000000000072bfa0 RCX: 0000000000462589
  48 RDX: 0000000000000000 RSI: 00000000200000c0 RDI: 0000000000000007
  49 RBP: 0000000000000005 R08: 0000000000001000 R09: 0000000000000000
  50 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb4b2c846bc
  51 R13: 00000000004bc733 R14: 00000000006f5138 R15: 00000000ffffffff
  52
  53 Allocated by task 4185:
  54  kasan_kmalloc+0xa0/0xd0
  55  __kmalloc+0x14a/0x350
  56  sk_prot_alloc+0xf6/0x290
  57  sk_alloc+0x3d/0xc00
  58  af_alg_accept+0x9e/0x670
  59  hash_accept+0x4a3/0x650
  60  __sys_accept4+0x306/0x5c0
  61  __x64_sys_accept4+0x98/0x100
  62  do_syscall_64+0xc8/0x580
  63  entry_SYSCALL_64_after_hwframe+0x49/0xbe
  64
  65 Freed by task 4184:
  66  __kasan_slab_free+0x12e/0x180
  67  kfree+0xeb/0x2f0
  68  __sk_destruct+0x4e6/0x6a0
  69  sk_destruct+0x48/0x70
  70  __sk_free+0xa9/0x270
  71  sk_free+0x2a/0x30
  72  af_alg_release+0x5c/0x70
  73  __sock_release+0xd3/0x280
  74  sock_close+0x1a/0x20
  75  __fput+0x27f/0x7f0
  76  task_work_run+0x136/0x1b0
  77  exit_to_usermode_loop+0x1a7/0x1d0
  78  do_syscall_64+0x461/0x580
  79  entry_SYSCALL_64_after_hwframe+0x49/0xbe
  80
  81 Syzkaller reproducer:
  82 r0 = perf_event_open(&(0x7f0000000000)={0x0, 0x70, 0x0, 0x0, 0x0, 0x0,
  83 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
  84 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
  85 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, @perf_config_ext}, 0x0, 0x0,
  86 0xffffffffffffffff, 0x0)
  87 r1 = socket$alg(0x26, 0x5, 0x0)
  88 getrusage(0x0, 0x0)
  89 bind(r1, &(0x7f00000001c0)=@alg={0x26, 'hash\x00', 0x0, 0x0,
  90 'sha256-ssse3\x00'}, 0x80)
  91 r2 = accept(r1, 0x0, 0x0)
  92 r3 = accept4$unix(r2, 0x0, 0x0, 0x0)
  93 r4 = dup3(r3, r0, 0x0)
  94 fchownat(r4, &(0x7f00000000c0)='\x00', 0x0, 0x0, 0x1000)
  95
  96 Fixes: 6d8c50dcb029 ("socket: close race condition between sock_close() and sockfs_setattr()")
  97 Signed-off-by: Mao Wenan <maowenan@huawei.com>
  98 Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
  99 ---
 100  crypto/af_alg.c | 4 +++-
 101  1 file changed, 3 insertions(+), 1 deletion(-)
 102
 103 diff --git a/crypto/af_alg.c b/crypto/af_alg.c
 104 index 671e42ff21d4..493002afae73 100644
 105 --- a/crypto/af_alg.c
 106 +++ b/crypto/af_alg.c
 107 @@ -122,8 +122,10 @@ static void alg_do_release(const struct af_alg_type *type, void *private)
 108
 109  int af_alg_release(struct socket *sock)
 110  {
 111 -       if (sock->sk)
 112 +       if (sock->sk) {
 113                 sock_put(sock->sk);
 114 +               sock->sk = NULL;
 115 +       }
 116         return 0;
 117  }
 118  EXPORT_SYMBOL_GPL(af_alg_release);