releases/4.19.35/sctp-initialize-_pad-of-sockaddr_in-before-copying-t.patch

   1 From 945e7404a83d79f1afac000f7f504054bab01f0c Mon Sep 17 00:00:00 2001
   2 From: Xin Long <lucien.xin@gmail.com>
   3 Date: Sun, 31 Mar 2019 16:58:15 +0800
   4 Subject: sctp: initialize _pad of sockaddr_in before copying to user memory
   5
   6 [ Upstream commit 09279e615c81ce55e04835970601ae286e3facbe ]
   7
   8 Syzbot report a kernel-infoleak:
   9
  10   BUG: KMSAN: kernel-infoleak in _copy_to_user+0x16b/0x1f0 lib/usercopy.c:32
  11   Call Trace:
  12     _copy_to_user+0x16b/0x1f0 lib/usercopy.c:32
  13     copy_to_user include/linux/uaccess.h:174 [inline]
  14     sctp_getsockopt_peer_addrs net/sctp/socket.c:5911 [inline]
  15     sctp_getsockopt+0x1668e/0x17f70 net/sctp/socket.c:7562
  16     ...
  17   Uninit was stored to memory at:
  18     sctp_transport_init net/sctp/transport.c:61 [inline]
  19     sctp_transport_new+0x16d/0x9a0 net/sctp/transport.c:115
  20     sctp_assoc_add_peer+0x532/0x1f70 net/sctp/associola.c:637
  21     sctp_process_param net/sctp/sm_make_chunk.c:2548 [inline]
  22     sctp_process_init+0x1a1b/0x3ed0 net/sctp/sm_make_chunk.c:2361
  23     ...
  24   Bytes 8-15 of 16 are uninitialized
  25
  26 It was caused by that th _pad field (the 8-15 bytes) of a v4 addr (saved in
  27 struct sockaddr_in) wasn't initialized, but directly copied to user memory
  28 in sctp_getsockopt_peer_addrs().
  29
  30 So fix it by calling memset(addr->v4.sin_zero, 0, 8) to initialize _pad of
  31 sockaddr_in before copying it to user memory in sctp_v4_addr_to_user(), as
  32 sctp_v6_addr_to_user() does.
  33
  34 Reported-by: syzbot+86b5c7c236a22616a72f@syzkaller.appspotmail.com
  35 Signed-off-by: Xin Long <lucien.xin@gmail.com>
  36 Tested-by: Alexander Potapenko <glider@google.com>
  37 Acked-by: Neil Horman <nhorman@tuxdriver.com>
  38 Signed-off-by: David S. Miller <davem@davemloft.net>
  39 Signed-off-by: Sasha Levin <sashal@kernel.org>
  40 ---
  41  net/sctp/protocol.c | 1 +
  42  1 file changed, 1 insertion(+)
  43
  44 diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
  45 index 1c9f079e8a50..d97b2b4b7a8b 100644
  46 --- a/net/sctp/protocol.c
  47 +++ b/net/sctp/protocol.c
  48 @@ -600,6 +600,7 @@ static struct sock *sctp_v4_create_accept_sk(struct sock *sk,
  49  static int sctp_v4_addr_to_user(struct sctp_sock *sp, union sctp_addr *addr)
  50  {
  51         /* No address mapping for V4 sockets */
  52 +       memset(addr->v4.sin_zero, 0, sizeof(addr->v4.sin_zero));
  53         return sizeof(struct sockaddr_in);
  54  }
  55
  56 --
  57 2.19.1
  58