Re: KASAN: use-after-free Read in tcp_current_mss

[Paolo Abeni]

On Wed, 2021-02-17 at 07:36 -0800, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    773dc50d Merge branch 'Xilinx-axienet-updates'
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=13460822d00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=dbc1ca9e55dc1f9f
> dashboard link: https://syzkaller.appspot.com/bug?extid=ea948c9d0dedf6ff57b1
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+ea948c9d0dedf6ff57b1@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ==================================================================
> BUG: KASAN: use-after-free in dst_mtu include/net/dst.h:201 [inline]
> BUG: KASAN: use-after-free in tcp_current_mss+0x358/0x360 net/ipv4/tcp_output.c:1835
> Read of size 8 at addr ffff88802943db08 by task syz-executor.2/11568
> 
> CPU: 0 PID: 11568 Comm: syz-executor.2 Not tainted 5.11.0-rc7-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:79 [inline]
>  dump_stack+0x107/0x163 lib/dump_stack.c:120
>  print_address_description.constprop.0.cold+0x5b/0x2f8 mm/kasan/report.c:230
>  __kasan_report mm/kasan/report.c:396 [inline]
>  kasan_report.cold+0x79/0xd5 mm/kasan/report.c:413
>  dst_mtu include/net/dst.h:201 [inline]
>  tcp_current_mss+0x358/0x360 net/ipv4/tcp_output.c:1835
>  tcp_send_mss+0x28/0x2b0 net/ipv4/tcp.c:943
>  mptcp_sendmsg_frag+0x13b/0x1220 net/mptcp/protocol.c:1266
>  mptcp_push_pending+0x2cc/0x650 net/mptcp/protocol.c:1477
>  mptcp_sendmsg+0x1ffb/0x2830 net/mptcp/protocol.c:1692
>  inet6_sendmsg+0x99/0xe0 net/ipv6/af_inet6.c:638
>  sock_sendmsg_nosec net/socket.c:652 [inline]
>  sock_sendmsg+0xcf/0x120 net/socket.c:672
>  sock_write_iter+0x289/0x3c0 net/socket.c:999
>  call_write_iter include/linux/fs.h:1901 [inline]
>  new_sync_write+0x426/0x650 fs/read_write.c:518
>  vfs_write+0x791/0xa30 fs/read_write.c:605
>  ksys_write+0x1ee/0x250 fs/read_write.c:658
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x465d99
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fc692d89188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 000000000056c0b0 RCX: 0000000000465d99
> RDX: 0000000000000001 RSI: 0000000020000000 RDI: 0000000000000003
> RBP: 00000000004bcf27 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c0b0
> R13: 00007ffc258487df R14: 00007fc692d89300 R15: 0000000000022000
> 
> Allocated by task 11558:
>  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
>  kasan_set_track mm/kasan/common.c:46 [inline]
>  set_alloc_info mm/kasan/common.c:401 [inline]
>  ____kasan_kmalloc.constprop.0+0x82/0xa0 mm/kasan/common.c:429
>  kasan_slab_alloc include/linux/kasan.h:209 [inline]
>  slab_post_alloc_hook mm/slab.h:512 [inline]
>  slab_alloc_node mm/slub.c:2892 [inline]
>  slab_alloc mm/slub.c:2900 [inline]
>  kmem_cache_alloc+0x1c6/0x440 mm/slub.c:2905
>  dst_alloc+0x9e/0x650 net/core/dst.c:93
>  rt_dst_alloc+0x73/0x430 net/ipv4/route.c:1642
>  __mkroute_output net/ipv4/route.c:2457 [inline]
>  ip_route_output_key_hash_rcu+0x955/0x2ce0 net/ipv4/route.c:2684
>  ip_route_output_key_hash+0x1a4/0x2f0 net/ipv4/route.c:2512
>  __ip_route_output_key include/net/route.h:126 [inline]
>  ip_route_output_flow+0x23/0x150 net/ipv4/route.c:2773
>  ip_route_newports include/net/route.h:342 [inline]
>  tcp_v4_connect+0x12d7/0x1c40 net/ipv4/tcp_ipv4.c:281
>  tcp_v6_connect+0x733/0x1df0 net/ipv6/tcp_ipv6.c:248
>  __inet_stream_connect+0x8c5/0xee0 net/ipv4/af_inet.c:661
>  inet_stream_connect+0x53/0xa0 net/ipv4/af_inet.c:725
>  mptcp_stream_connect+0x156/0x800 net/mptcp/protocol.c:3200
>  __sys_connect_file+0x155/0x1a0 net/socket.c:1835
>  __sys_connect+0x161/0x190 net/socket.c:1852
>  __do_sys_connect net/socket.c:1862 [inline]
>  __se_sys_connect net/socket.c:1859 [inline]
>  __x64_sys_connect+0x6f/0xb0 net/socket.c:1859
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Freed by task 11559:
>  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
>  kasan_set_track+0x1c/0x30 mm/kasan/common.c:46
>  kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:356
>  ____kasan_slab_free+0xe1/0x110 mm/kasan/common.c:362
>  kasan_slab_free include/linux/kasan.h:192 [inline]
>  slab_free_hook mm/slub.c:1547 [inline]
>  slab_free_freelist_hook+0x5d/0x150 mm/slub.c:1580
>  slab_free mm/slub.c:3143 [inline]
>  kmem_cache_free+0x82/0x350 mm/slub.c:3159
>  dst_destroy+0x2bc/0x3c0 net/core/dst.c:129
>  rcu_do_batch kernel/rcu/tree.c:2489 [inline]
>  rcu_core+0x5eb/0xf00 kernel/rcu/tree.c:2723
>  __do_softirq+0x29b/0x9f6 kernel/softirq.c:343
> 
> Last potentially related work creation:
>  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
>  kasan_record_aux_stack+0xc5/0xf0 mm/kasan/generic.c:344
>  __call_rcu kernel/rcu/tree.c:2965 [inline]
>  call_rcu+0xbb/0x700 kernel/rcu/tree.c:3038
>  dst_release net/core/dst.c:179 [inline]
>  dst_release+0x79/0xe0 net/core/dst.c:169
>  tcp_disconnect+0xc26/0x1ec0 net/ipv4/tcp.c:3003
>  __tcp_close+0x486/0x1170 net/ipv4/tcp.c:2745
>  tcp_close+0x29/0xc0 net/ipv4/tcp.c:2867
>  inet_release+0x12e/0x280 net/ipv4/af_inet.c:431
>  inet6_release+0x4c/0x70 net/ipv6/af_inet6.c:475
>  __sock_release net/socket.c:597 [inline]
>  sock_release+0x87/0x1b0 net/socket.c:625
>  rds_tcp_accept_one+0x5fc/0xc10 net/rds/tcp_listen.c:220
>  rds_tcp_accept_worker+0x50/0x80 net/rds/tcp.c:515
>  process_one_work+0x98d/0x15f0 kernel/workqueue.c:2275
>  worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
>  kthread+0x3b1/0x4a0 kernel/kthread.c:292
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
> 
> Second to last potentially related work creation:
>  kasan_save_stack+0x1b/0x40 mm/kasan/common.c:38
>  kasan_record_aux_stack+0xc5/0xf0 mm/kasan/generic.c:344
>  __call_rcu kernel/rcu/tree.c:2965 [inline]
>  call_rcu+0xbb/0x700 kernel/rcu/tree.c:3038
>  dst_release net/core/dst.c:179 [inline]
>  dst_release+0x79/0xe0 net/core/dst.c:169
>  inet_sock_destruct+0x600/0x830 net/ipv4/af_inet.c:160
>  __sk_destruct+0x4b/0x900 net/core/sock.c:1795
>  rcu_do_batch kernel/rcu/tree.c:2489 [inline]
>  rcu_core+0x5eb/0xf00 kernel/rcu/tree.c:2723
>  __do_softirq+0x29b/0x9f6 kernel/softirq.c:343
> 
> The buggy address belongs to the object at ffff88802943db00
>  which belongs to the cache ip_dst_cache of size 176
> The buggy address is located 8 bytes inside of
>  176-byte region [ffff88802943db00, ffff88802943dbb0)
> The buggy address belongs to the page:
> page:0000000019369b4d refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2943d
> flags: 0xfff00000000200(slab)
> raw: 00fff00000000200 dead000000000100 dead000000000122 ffff888141745a00
> raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
>  ffff88802943da00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>  ffff88802943da80: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
> > ffff88802943db00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>                       ^
>  ffff88802943db80: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
>  ffff88802943dc00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> ==================================================================

Even this one...

#syz dup: WARNING in dst_release

/P