Garbage supplied by user will cause to UCMA module provide zero
memory size for memcpy(), because it wasn't checked, it will
produce unpredictable results in rdma_resolve_addr().

[   42.873814] BUG: KASAN: null-ptr-deref in rdma_resolve_addr+0xc8/0xfb0
[   42.874816] Write of size 28 at addr 00000000000000a0 by task resaddr/1044
[   42.876765]
[   42.876960] CPU: 1 PID: 1044 Comm: resaddr Not tainted 4.16.0-rc1-00057-gaa56a5293d7e #34
[   42.877840] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.11.0-0-g63451fca13-prebuilt.qemu-project.org 04/01/2014
[   42.879691] Call Trace:
[   42.880236]  dump_stack+0x5c/0x77
[   42.880664]  kasan_report+0x163/0x380
[   42.881354]  ? rdma_resolve_addr+0xc8/0xfb0
[   42.881864]  memcpy+0x34/0x50
[   42.882692]  rdma_resolve_addr+0xc8/0xfb0
[   42.883366]  ? deref_stack_reg+0x88/0xd0
[   42.883856]  ? vsnprintf+0x31a/0x770
[   42.884686]  ? rdma_bind_addr+0xc40/0xc40
[   42.885327]  ? num_to_str+0x130/0x130
[   42.885773]  ? deref_stack_reg+0x88/0xd0
[   42.886217]  ? __read_once_size_nocheck.constprop.6+0x10/0x10
[   42.887698]  ? unwind_get_return_address_ptr+0x50/0x50
[   42.888302]  ? replace_slot+0x147/0x170
[   42.889176]  ? delete_node+0x12c/0x340
[   42.890223]  ? __radix_tree_lookup+0xa9/0x160
[   42.891196]  ? ucma_resolve_ip+0xb7/0x110
[   42.891917]  ucma_resolve_ip+0xb7/0x110
[   42.893003]  ? ucma_resolve_addr+0x190/0x190
[   42.893531]  ? _copy_from_user+0x5e/0x90
[   42.894204]  ucma_write+0x174/0x1f0
[   42.895162]  ? ucma_resolve_route+0xf0/0xf0
[   42.896309]  ? dequeue_task_fair+0x67e/0xd90
[   42.897192]  ? put_prev_entity+0x7d/0x170
[   42.897870]  ? ring_buffer_record_is_on+0xd/0x20
[   42.898439]  ? tracing_record_taskinfo_skip+0x20/0x50
[   42.899686]  __vfs_write+0xc4/0x350
[   42.900142]  ? kernel_read+0xa0/0xa0
[   42.900602]  ? firmware_map_remove+0xdf/0xdf
[   42.901135]  ? do_task_dead+0x5d/0x60
[   42.901598]  ? do_exit+0xcc6/0x1220
[   42.902789]  ? __fget+0xa8/0xf0
[   42.903190]  vfs_write+0xf7/0x280
[   42.903600]  SyS_write+0xa1/0x120
[   42.904206]  ? SyS_read+0x120/0x120
[   42.905710]  ? compat_start_thread+0x60/0x60
[   42.906423]  ? SyS_read+0x120/0x120
[   42.908716]  do_syscall_64+0xeb/0x250
[   42.910760]  entry_SYSCALL_64_after_hwframe+0x21/0x86
[   42.912735] RIP: 0033:0x7f138b0afe99
[   42.914734] RSP: 002b:00007f138b799e98 EFLAGS: 00000287 ORIG_RAX: 0000000000000001
[   42.917134] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f138b0afe99
[   42.919487] RDX: 000000000000002e RSI: 0000000020000c40 RDI: 0000000000000004
[   42.922393] RBP: 00007f138b799ec0 R08: 00007f138b79a700 R09: 0000000000000000
[   42.925266] R10: 00007f138b79a700 R11: 0000000000000287 R12: 00007f138b799fc0
[   42.927570] R13: 0000000000000000 R14: 00007ffdbae757c0 R15: 00007f138b79a9c0
[   42.930047]
[   42.932681] Disabling lock debugging due to kernel taint
[   42.934795] BUG: unable to handle kernel NULL pointer dereference at 00000000000000a0
[   42.936939] IP: memcpy_erms+0x6/0x10
[   42.938864] PGD 80000001bea92067 P4D 80000001bea92067 PUD 1bea96067 PMD 0
[   42.941576] Oops: 0002 [#1] SMP KASAN PTI
[   42.943952] CPU: 1 PID: 1044 Comm: resaddr Tainted: G    B 4.16.0-rc1-00057-gaa56a5293d7e #34
[   42.946964] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.11.0-0-g63451fca13-prebuilt.qemu-project.org 04/01/2014
[   42.952336] RIP: 0010:memcpy_erms+0x6/0x10
[   42.954707] RSP: 0018:ffff8801c8b479c8 EFLAGS: 00010286
[   42.957227] RAX: 00000000000000a0 RBX: ffff8801c8b47ba0 RCX: 000000000000001c
[   42.960543] RDX: 000000000000001c RSI: ffff8801c8b47bbc RDI: 00000000000000a0
[   42.963867] RBP: ffff8801c8b47b60 R08: 0000000000000000 R09: ffffed0039168ed1
[   42.967303] R10: 0000000000000001 R11: ffffed0039168ed0 R12: ffff8801c8b47bbc
[   42.970685] R13: 00000000000000a0 R14: 1ffff10039168f4a R15: 0000000000000000
[   42.973631] FS:  00007f138b79a700(0000) GS:ffff8801e5d00000(0000) knlGS:0000000000000000
[   42.976831] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[   42.979239] CR2: 00000000000000a0 CR3: 00000001be908002 CR4: 00000000003606a0
[   42.982060] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[   42.984877] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[   42.988033] Call Trace:
[   42.990487]  rdma_resolve_addr+0xc8/0xfb0
[   42.993202]  ? deref_stack_reg+0x88/0xd0
[   42.996055]  ? vsnprintf+0x31a/0x770
[   42.998707]  ? rdma_bind_addr+0xc40/0xc40
[   43.000985]  ? num_to_str+0x130/0x130
[   43.003410]  ? deref_stack_reg+0x88/0xd0
[   43.006302]  ? __read_once_size_nocheck.constprop.6+0x10/0x10
[   43.008780]  ? unwind_get_return_address_ptr+0x50/0x50
[   43.011178]  ? replace_slot+0x147/0x170
[   43.013517]  ? delete_node+0x12c/0x340
[   43.016019]  ? __radix_tree_lookup+0xa9/0x160
[   43.018755]  ? ucma_resolve_ip+0xb7/0x110
[   43.021270]  ucma_resolve_ip+0xb7/0x110
[   43.023968]  ? ucma_resolve_addr+0x190/0x190
[   43.026312]  ? _copy_from_user+0x5e/0x90
[   43.029384]  ucma_write+0x174/0x1f0
[   43.031861]  ? ucma_resolve_route+0xf0/0xf0
[   43.034782]  ? dequeue_task_fair+0x67e/0xd90
[   43.037483]  ? put_prev_entity+0x7d/0x170
[   43.040215]  ? ring_buffer_record_is_on+0xd/0x20
[   43.042990]  ? tracing_record_taskinfo_skip+0x20/0x50
[   43.045595]  __vfs_write+0xc4/0x350
[   43.048624]  ? kernel_read+0xa0/0xa0
[   43.051604]  ? firmware_map_remove+0xdf/0xdf
[   43.055379]  ? do_task_dead+0x5d/0x60
[   43.058000]  ? do_exit+0xcc6/0x1220
[   43.060783]  ? __fget+0xa8/0xf0
[   43.063133]  vfs_write+0xf7/0x280
[   43.065677]  SyS_write+0xa1/0x120
[   43.068647]  ? SyS_read+0x120/0x120
[   43.071179]  ? compat_start_thread+0x60/0x60
[   43.074025]  ? SyS_read+0x120/0x120
[   43.076705]  do_syscall_64+0xeb/0x250
[   43.079006]  entry_SYSCALL_64_after_hwframe+0x21/0x86
[   43.081606] RIP: 0033:0x7f138b0afe99
[   43.083679] RSP: 002b:00007f138b799e98 EFLAGS: 00000287 ORIG_RAX: 0000000000000001
[   43.086802] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f138b0afe99
[   43.089989] RDX: 000000000000002e RSI: 0000000020000c40 RDI: 0000000000000004
[   43.092866] RBP: 00007f138b799ec0 R08: 00007f138b79a700 R09: 0000000000000000
[   43.096233] R10: 00007f138b79a700 R11: 0000000000000287 R12: 00007f138b799fc0
[   43.098913] R13: 0000000000000000 R14: 00007ffdbae757c0 R15: 00007f138b79a9c0
[   43.101809] Code: 90 90 90 90 90 eb 1e 0f 1f 00 48 89 f8 48 89 d1 48
c1 e9 03 83 e2 07 f3 48 a5 89 d1 f3 a4 c3 66 0f 1f 44 00 00 48 89 f8 48
89 d1 <f3> a4 c3 0f 1f 80 00 00 00 00 48 89 f8 48 83 fa 20 72 7e 40 38
[   43.107950] RIP: memcpy_erms+0x6/0x10 RSP: ffff8801c8b479c8

Reported-by:  <syzbot+1d8c43206853b369d00c@syzkaller.appspotmail.com>
Fixes: 75216638

 ("RDMA/cma: Export rdma cm interface to userspace")
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>