queue-4.14/net-rose-fix-a-possible-stack-overflow.patch

   1 From foo@baz Thu Mar 28 21:57:57 CET 2019
   2 From: Eric Dumazet <edumazet@google.com>
   3 Date: Fri, 15 Mar 2019 10:41:14 -0700
   4 Subject: net: rose: fix a possible stack overflow
   5
   6 From: Eric Dumazet <edumazet@google.com>
   7
   8 [ Upstream commit e5dcc0c3223c45c94100f05f28d8ef814db3d82c ]
   9
  10 rose_write_internal() uses a temp buffer of 100 bytes, but a manual
  11 inspection showed that given arbitrary input, rose_create_facilities()
  12 can fill up to 110 bytes.
  13
  14 Lets use a tailroom of 256 bytes for peace of mind, and remove
  15 the bounce buffer : we can simply allocate a big enough skb
  16 and adjust its length as needed.
  17
  18 syzbot report :
  19
  20 BUG: KASAN: stack-out-of-bounds in memcpy include/linux/string.h:352 [inline]
  21 BUG: KASAN: stack-out-of-bounds in rose_create_facilities net/rose/rose_subr.c:521 [inline]
  22 BUG: KASAN: stack-out-of-bounds in rose_write_internal+0x597/0x15d0 net/rose/rose_subr.c:116
  23 Write of size 7 at addr ffff88808b1ffbef by task syz-executor.0/24854
  24
  25 CPU: 0 PID: 24854 Comm: syz-executor.0 Not tainted 5.0.0+ #97
  26 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
  27 Call Trace:
  28  __dump_stack lib/dump_stack.c:77 [inline]
  29  dump_stack+0x172/0x1f0 lib/dump_stack.c:113
  30  print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187
  31  kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317
  32  check_memory_region_inline mm/kasan/generic.c:185 [inline]
  33  check_memory_region+0x123/0x190 mm/kasan/generic.c:191
  34  memcpy+0x38/0x50 mm/kasan/common.c:131
  35  memcpy include/linux/string.h:352 [inline]
  36  rose_create_facilities net/rose/rose_subr.c:521 [inline]
  37  rose_write_internal+0x597/0x15d0 net/rose/rose_subr.c:116
  38  rose_connect+0x7cb/0x1510 net/rose/af_rose.c:826
  39  __sys_connect+0x266/0x330 net/socket.c:1685
  40  __do_sys_connect net/socket.c:1696 [inline]
  41  __se_sys_connect net/socket.c:1693 [inline]
  42  __x64_sys_connect+0x73/0xb0 net/socket.c:1693
  43  do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290
  44  entry_SYSCALL_64_after_hwframe+0x49/0xbe
  45 RIP: 0033:0x458079
  46 Code: ad b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00
  47 RSP: 002b:00007f47b8d9dc78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
  48 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458079
  49 RDX: 000000000000001c RSI: 0000000020000040 RDI: 0000000000000004
  50 RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
  51 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f47b8d9e6d4
  52 R13: 00000000004be4a4 R14: 00000000004ceca8 R15: 00000000ffffffff
  53
  54 The buggy address belongs to the page:
  55 page:ffffea00022c7fc0 count:0 mapcount:0 mapping:0000000000000000 index:0x0
  56 flags: 0x1fffc0000000000()
  57 raw: 01fffc0000000000 0000000000000000 ffffffff022c0101 0000000000000000
  58 raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
  59 page dumped because: kasan: bad access detected
  60
  61 Memory state around the buggy address:
  62  ffff88808b1ffa80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  63  ffff88808b1ffb00: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 00 00 03
  64 >ffff88808b1ffb80: f2 f2 00 00 00 00 00 00 00 00 00 00 00 00 04 f3
  65                                                              ^
  66  ffff88808b1ffc00: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
  67  ffff88808b1ffc80: 00 00 00 00 00 00 00 f1 f1 f1 f1 f1 f1 01 f2 01
  68
  69 Signed-off-by: Eric Dumazet <edumazet@google.com>
  70 Reported-by: syzbot <syzkaller@googlegroups.com>
  71 Signed-off-by: David S. Miller <davem@davemloft.net>
  72 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  73 ---
  74  net/rose/rose_subr.c |   21 ++++++++++++---------
  75  1 file changed, 12 insertions(+), 9 deletions(-)
  76
  77 --- a/net/rose/rose_subr.c
  78 +++ b/net/rose/rose_subr.c
  79 @@ -105,16 +105,17 @@ void rose_write_internal(struct sock *sk
  80         struct sk_buff *skb;
  81         unsigned char  *dptr;
  82         unsigned char  lci1, lci2;
  83 -       char buffer[100];
  84 -       int len, faclen = 0;
  85 +       int maxfaclen = 0;
  86 +       int len, faclen;
  87 +       int reserve;
  88
  89 -       len = AX25_BPQ_HEADER_LEN + AX25_MAX_HEADER_LEN + ROSE_MIN_LEN + 1;
  90 +       reserve = AX25_BPQ_HEADER_LEN + AX25_MAX_HEADER_LEN + 1;
  91 +       len = ROSE_MIN_LEN;
  92
  93         switch (frametype) {
  94         case ROSE_CALL_REQUEST:
  95                 len   += 1 + ROSE_ADDR_LEN + ROSE_ADDR_LEN;
  96 -               faclen = rose_create_facilities(buffer, rose);
  97 -               len   += faclen;
  98 +               maxfaclen = 256;
  99                 break;
 100         case ROSE_CALL_ACCEPTED:
 101         case ROSE_CLEAR_REQUEST:
 102 @@ -123,15 +124,16 @@ void rose_write_internal(struct sock *sk
 103                 break;
 104         }
 105
 106 -       if ((skb = alloc_skb(len, GFP_ATOMIC)) == NULL)
 107 +       skb = alloc_skb(reserve + len + maxfaclen, GFP_ATOMIC);
 108 +       if (!skb)
 109                 return;
 110
 111         /*
 112          *      Space for AX.25 header and PID.
 113          */
 114 -       skb_reserve(skb, AX25_BPQ_HEADER_LEN + AX25_MAX_HEADER_LEN + 1);
 115 +       skb_reserve(skb, reserve);
 116
 117 -       dptr = skb_put(skb, skb_tailroom(skb));
 118 +       dptr = skb_put(skb, len);
 119
 120         lci1 = (rose->lci >> 8) & 0x0F;
 121         lci2 = (rose->lci >> 0) & 0xFF;
 122 @@ -146,7 +148,8 @@ void rose_write_internal(struct sock *sk
 123                 dptr   += ROSE_ADDR_LEN;
 124                 memcpy(dptr, &rose->source_addr, ROSE_ADDR_LEN);
 125                 dptr   += ROSE_ADDR_LEN;
 126 -               memcpy(dptr, buffer, faclen);
 127 +               faclen = rose_create_facilities(dptr, rose);
 128 +               skb_put(skb, faclen);
 129                 dptr   += faclen;
 130                 break;
 131