• Eric Dumazet's avatar
    dccp: do not release listeners too soon · c3f24cfb
    Eric Dumazet authored
    Andrey Konovalov reported following error while fuzzing with syzkaller :
    
    IPv4: Attempt to release alive inet socket ffff880068e98940
    kasan: CONFIG_KASAN_INLINE enabled
    kasan: GPF could be caused by NULL-ptr deref or user memory access
    general protection fault: 0000 [#1] SMP KASAN
    Modules linked in:
    CPU: 1 PID: 3905 Comm: a.out Not tainted 4.9.0-rc3+ #333
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
    task: ffff88006b9e0000 task.stack: ffff880068770000
    RIP: 0010:[<ffffffff819ead5f>]  [<ffffffff819ead5f>]
    selinux_socket_sock_rcv_skb+0xff/0x6a0 security/selinux/hooks.c:4639
    RSP: 0018:ffff8800687771c8  EFLAGS: 00010202
    RAX: ffff88006b9e0000 RBX: 1ffff1000d0eee3f RCX: 1ffff1000d1d312a
    RDX: 1ffff1000d1d31a6 RSI: dffffc0000000000 RDI: 0000000000000010
    RBP: ffff880068777360 R08: 0000000000000000 R09: 0000000000000002
    R10: dffffc0000000000 R11: 0000000000000006 R12: ffff880068e98940
    R13: 0000000000000002 R14: ffff880068777338 R15: 0000000000000000
    FS:  00007f00ff760700(0000) GS:ffff88006cd00000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 0000000020008000 CR3: 000000006a308000 CR4: 00000000000006e0
    Stack:
     ffff8800687771e0 ffffffff812508a5 ffff8800686f3168 0000000000000007
     ffff88006ac8cdfc ffff8800665ea500 0000000041b58ab3 ffffffff847b5480
     ffffffff819eac60 ffff88006b9e0860 ffff88006b9e0868 ffff88006b9e07f0
    Call Trace:
     [<ffffffff819c8dd5>] security_sock_rcv_skb+0x75/0xb0 security/security.c:1317
     [<ffffffff82c2a9e7>] sk_filter_trim_cap+0x67/0x10e0 net/core/filter.c:81
     [<ffffffff82b81e60>] __sk_receive_skb+0x30/0xa00 net/core/sock.c:460
     [<ffffffff838bbf12>] dccp_v4_rcv+0xdb2/0x1910 net/dccp/ipv4.c:873
     [<ffffffff83069d22>] ip_local_deliver_finish+0x332/0xad0
    net/ipv4/ip_input.c:216
     [<     inline     >] NF_HOOK_THRESH ./include/linux/netfilter.h:232
     [<     inline     >] NF_HOOK ./include/linux/netfilter.h:255
     [<ffffffff8306abd2>] ip_local_deliver+0x1c2/0x4b0 net/ipv4/ip_input.c:257
     [<     inline     >] dst_input ./include/net/dst.h:507
     [<ffffffff83068500>] ip_rcv_finish+0x750/0x1c40 net/ipv4/ip_input.c:396
     [<     inline     >] NF_HOOK_THRESH ./include/linux/netfilter.h:232
     [<     inline     >] NF_HOOK ./include/linux/netfilter.h:255
     [<ffffffff8306b82f>] ip_rcv+0x96f/0x12f0 net/ipv4/ip_input.c:487
     [<ffffffff82bd9fb7>] __netif_receive_skb_core+0x1897/0x2a50 net/core/dev.c:4213
     [<ffffffff82bdb19a>] __netif_receive_skb+0x2a/0x170 net/core/dev.c:4251
     [<ffffffff82bdb493>] netif_receive_skb_internal+0x1b3/0x390 net/core/dev.c:4279
     [<ffffffff82bdb6b8>] netif_receive_skb+0x48/0x250 net/core/dev.c:4303
     [<ffffffff8241fc75>] tun_get_user+0xbd5/0x28a0 drivers/net/tun.c:1308
     [<ffffffff82421b5a>] tun_chr_write_iter+0xda/0x190 drivers/net/tun.c:1332
     [<     inline     >] new_sync_write fs/read_write.c:499
     [<ffffffff8151bd44>] __vfs_write+0x334/0x570 fs/read_write.c:512
     [<ffffffff8151f85b>] vfs_write+0x17b/0x500 fs/read_write.c:560
     [<     inline     >] SYSC_write fs/read_write.c:607
     [<ffffffff81523184>] SyS_write+0xd4/0x1a0 fs/read_write.c:599
     [<ffffffff83fc02c1>] entry_SYSCALL_64_fastpath+0x1f/0xc2
    
    It turns out DCCP calls __sk_receive_skb(), and this broke when
    lookups no longer took a reference on listeners.
    
    Fix this issue by adding a @refcounted parameter to __sk_receive_skb(),
    so that sock_put() is used only when needed.
    
    Fixes: 3b24d854 ("tcp/dccp: do not touch listener sk_refcnt under synflood")
    Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
    Reported-by: default avatarAndrey Konovalov <andreyknvl@google.com>
    Tested-by: default avatarAndrey Konovalov <andreyknvl@google.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    c3f24cfb
sock.h 63.3 KB