releases/4.4.181/net-gro-fix-use-after-free-read-in-napi_gro_frags.patch

   1 From foo@baz Fri 31 May 2019 03:55:52 PM PDT
   2 From: Eric Dumazet <edumazet@google.com>
   3 Date: Wed, 29 May 2019 15:36:10 -0700
   4 Subject: net-gro: fix use-after-free read in napi_gro_frags()
   5
   6 From: Eric Dumazet <edumazet@google.com>
   7
   8 [ Upstream commit a4270d6795b0580287453ea55974d948393e66ef ]
   9
  10 If a network driver provides to napi_gro_frags() an
  11 skb with a page fragment of exactly 14 bytes, the call
  12 to gro_pull_from_frag0() will 'consume' the fragment
  13 by calling skb_frag_unref(skb, 0), and the page might
  14 be freed and reused.
  15
  16 Reading eth->h_proto at the end of napi_frags_skb() might
  17 read mangled data, or crash under specific debugging features.
  18
  19 BUG: KASAN: use-after-free in napi_frags_skb net/core/dev.c:5833 [inline]
  20 BUG: KASAN: use-after-free in napi_gro_frags+0xc6f/0xd10 net/core/dev.c:5841
  21 Read of size 2 at addr ffff88809366840c by task syz-executor599/8957
  22
  23 CPU: 1 PID: 8957 Comm: syz-executor599 Not tainted 5.2.0-rc1+ #32
  24 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
  25 Call Trace:
  26  __dump_stack lib/dump_stack.c:77 [inline]
  27  dump_stack+0x172/0x1f0 lib/dump_stack.c:113
  28  print_address_description.cold+0x7c/0x20d mm/kasan/report.c:188
  29  __kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
  30  kasan_report+0x12/0x20 mm/kasan/common.c:614
  31  __asan_report_load_n_noabort+0xf/0x20 mm/kasan/generic_report.c:142
  32  napi_frags_skb net/core/dev.c:5833 [inline]
  33  napi_gro_frags+0xc6f/0xd10 net/core/dev.c:5841
  34  tun_get_user+0x2f3c/0x3ff0 drivers/net/tun.c:1991
  35  tun_chr_write_iter+0xbd/0x156 drivers/net/tun.c:2037
  36  call_write_iter include/linux/fs.h:1872 [inline]
  37  do_iter_readv_writev+0x5f8/0x8f0 fs/read_write.c:693
  38  do_iter_write fs/read_write.c:970 [inline]
  39  do_iter_write+0x184/0x610 fs/read_write.c:951
  40  vfs_writev+0x1b3/0x2f0 fs/read_write.c:1015
  41  do_writev+0x15b/0x330 fs/read_write.c:1058
  42
  43 Fixes: a50e233c50db ("net-gro: restore frag0 optimization")
  44 Signed-off-by: Eric Dumazet <edumazet@google.com>
  45 Reported-by: syzbot <syzkaller@googlegroups.com>
  46 Signed-off-by: David S. Miller <davem@davemloft.net>
  47 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  48 ---
  49  net/core/dev.c |    2 +-
  50  1 file changed, 1 insertion(+), 1 deletion(-)
  51
  52 --- a/net/core/dev.c
  53 +++ b/net/core/dev.c
  54 @@ -4550,7 +4550,6 @@ static struct sk_buff *napi_frags_skb(st
  55         skb_reset_mac_header(skb);
  56         skb_gro_reset_offset(skb);
  57
  58 -       eth = skb_gro_header_fast(skb, 0);
  59         if (unlikely(skb_gro_header_hard(skb, hlen))) {
  60                 eth = skb_gro_header_slow(skb, hlen, 0);
  61                 if (unlikely(!eth)) {
  62 @@ -4558,6 +4557,7 @@ static struct sk_buff *napi_frags_skb(st
  63                         return NULL;
  64                 }
  65         } else {
  66 +               eth = (const struct ethhdr *)skb->data;
  67                 gro_pull_from_frag0(skb, hlen);
  68                 NAPI_GRO_CB(skb)->frag0 += hlen;
  69                 NAPI_GRO_CB(skb)->frag0_len -= hlen;