| Message ID | d7d7f946ab9c43e96720d97e68645e38fb8b233c.1590417507.git.pabeni@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [net] mptcp: avoid NULL-ptr derefence on fallback | expand |
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 1f52a0fa31ed..69b66423305b 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -954,7 +954,8 @@ static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, pr_debug("block timeout %ld", timeo); mptcp_wait_data(sk, &timeo); - if (unlikely(__mptcp_tcp_fallback(msk))) + ssock = __mptcp_tcp_fallback(msk); + if (unlikely(ssock)) goto fallback; }
In the MPTCP receive path we must cope with TCP fallback on blocking recvmsg(). Currently in such code path we detect the fallback condition, but we don't fetch the struct socket required for fallback. The above allowed syzkaller to trigger a NULL pointer dereference: general protection fault, probably for non-canonical address 0xdffffc0000000004: 0000 [#1] PREEMPT SMP KASAN KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027] CPU: 1 PID: 7226 Comm: syz-executor523 Not tainted 5.7.0-rc6-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 RIP: 0010:sock_recvmsg_nosec net/socket.c:886 [inline] RIP: 0010:sock_recvmsg+0x92/0x110 net/socket.c:904 Code: 5b 41 5c 41 5d 41 5e 41 5f 5d c3 44 89 6c 24 04 e8 53 18 1d fb 4d 8d 6f 20 4c 89 e8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 4c 89 ef e8 20 12 5b fb bd a0 00 00 00 49 03 6d RSP: 0018:ffffc90001077b98 EFLAGS: 00010202 RAX: 0000000000000004 RBX: ffffc90001077dc0 RCX: dffffc0000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: ffffffff86565e59 R09: ffffed10115afeaa R10: ffffed10115afeaa R11: 0000000000000000 R12: 1ffff9200020efbc R13: 0000000000000020 R14: ffffc90001077de0 R15: 0000000000000000 FS: 00007fc6a3abe700(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004d0050 CR3: 00000000969f0000 CR4: 00000000001406e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: mptcp_recvmsg+0x18d5/0x19b0 net/mptcp/protocol.c:891 inet_recvmsg+0xf6/0x1d0 net/ipv4/af_inet.c:838 sock_recvmsg_nosec net/socket.c:886 [inline] sock_recvmsg net/socket.c:904 [inline] __sys_recvfrom+0x2f3/0x470 net/socket.c:2057 __do_sys_recvfrom net/socket.c:2075 [inline] __se_sys_recvfrom net/socket.c:2071 [inline] __x64_sys_recvfrom+0xda/0xf0 net/socket.c:2071 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295 entry_SYSCALL_64_after_hwframe+0x49/0xb3 Address the issue initializing the struct socket reference before entering the fallback code. Reported-and-tested-by: syzbot+c6bfc3db991edc918432@syzkaller.appspotmail.com Suggested-by: Ondrej Mosnacek <omosnace@redhat.com> Fixes: 8ab183deb26a ("mptcp: cope with later TCP fallback") Signed-off-by: Paolo Abeni <pabeni@redhat.com> --- net/mptcp/protocol.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)