Subject: Re: RDS: sendto() with very large buffer triggering WARNING: at mm/page_alloc.c:2403

From: Venkat Venkatsubra <[email-masked]>
Date: Thu, 29 Nov 2012 13:38:32 -0600

On 11/29/2012 2:39 AM, Tommi Rantala wrote:
> Hello,
>
> Is RDS supposed to cap the sendto() buffer size? Saw the WARNING while
> fuzzing with Trinity.
>
> #include<string.h>
> #include<arpa/inet.h>
> #include<sys/socket.h>
>
> static const char buf[1234000567];
>
> int main(void)
> {
>          int fd;
>          struct sockaddr_in sa;
>
>          fd = socket(21 /* AF_RDS */, SOCK_SEQPACKET, 0);
>          if (fd<  0)
>                  return 1;
>
>          memset(&sa, 0, sizeof(sa));
>          sa.sin_family = AF_INET;
>          sa.sin_addr.s_addr = inet_addr("127.0.0.1");
>          sa.sin_port = htons(11111);
>
>          bind(fd, (struct sockaddr *)&sa, sizeof(sa));
>
>          sendto(fd, buf, sizeof(buf), 0, (struct sockaddr *)&sa, sizeof(sa));
>
>          return 0;
> }
>
> $ strace -e sendto ./rds-sendto
> sendto(3, "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"...,
> 1234000567, 0, {sa_family=AF_INET, sin_port=htons(11111),
> sin_addr=inet_addr("127.0.0.1")}, 16) = -1 ENOMEM (Cannot allocate
> memory)
>
> [ 7421.592595] ------------[ cut here ]------------
> [ 7421.592621] WARNING: at mm/page_alloc.c:2403
> __alloc_pages_nodemask+0x2c0/0x9f0()
> [ 7421.592628] Hardware name: EB1012
> [ 7421.592633] Modules linked in:
> [ 7421.592645] Pid: 3082, comm: rds-sendto Not tainted 3.7.0-rc7+ #58
> [ 7421.592650] Call Trace:
> [ 7421.592667]  [<ffffffff810a197b>] warn_slowpath_common+0x7b/0xc0
> [ 7421.592678]  [<ffffffff810a19d5>] warn_slowpath_null+0x15/0x20
> [ 7421.592689]  [<ffffffff81171900>] __alloc_pages_nodemask+0x2c0/0x9f0
> [ 7421.592700]  [<ffffffff81107c90>] ? __lock_acquire+0x3a0/0x9f0
> [ 7421.592711]  [<ffffffff81107c90>] ? __lock_acquire+0x3a0/0x9f0
> [ 7421.592724]  [<ffffffff811ac6bf>] alloc_pages_current+0x7f/0xf0
> [ 7421.592735]  [<ffffffff8116cc19>] __get_free_pages+0x9/0x40
> [ 7421.592746]  [<ffffffff811b3d8a>] kmalloc_order_trace+0x3a/0x190
> [ 7421.592755]  [<ffffffff81107c90>] ? __lock_acquire+0x3a0/0x9f0
> [ 7421.592765]  [<ffffffff811b4f59>] __kmalloc+0x229/0x240
> [ 7421.592778]  [<ffffffff81d1b06e>] rds_message_alloc+0x1e/0xa0
> [ 7421.592789]  [<ffffffff81d1db66>] rds_sendmsg+0x196/0x720
> [ 7421.592802]  [<ffffffff81a72a80>] ? sock_update_classid+0xf0/0x2b0
> [ 7421.592813]  [<ffffffff81a6abec>] sock_sendmsg+0xdc/0xf0
> [ 7421.592828]  [<ffffffff8118e9e5>] ? might_fault+0x85/0x90
> [ 7421.592838]  [<ffffffff8118e99c>] ? might_fault+0x3c/0x90
> [ 7421.592848]  [<ffffffff81a6e0fa>] sys_sendto+0xfa/0x130
> [ 7421.592859]  [<ffffffff8110953d>] ? trace_hardirqs_on_caller+0x10d/0x1a0
> [ 7421.592868]  [<ffffffff811095dd>] ? trace_hardirqs_on+0xd/0x10
> [ 7421.592881]  [<ffffffff81e94c9d>] ? _raw_spin_unlock_irq+0x3d/0x70
> [ 7421.592892]  [<ffffffff810bab44>] ? ptrace_notify+0x74/0x90
> [ 7421.592904]  [<ffffffff81e96250>] tracesys+0xdd/0xe2
> [ 7421.592911] ---[ end trace d9d681d0d60abf69 ]---
>
> Tommi
> --
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The man page of rds says this:
        The  default values for the send and receive buffer size are 
controlled
        by the A given  RDS  socket  has  limited  transmit  buffer  
space.  It
        defaults  to  the  system  wide  socket  send  buffer  size  set 
in the
        wmem_default and rmem_default sysctls, respectively. They can 
be  tuned
        by  the application through the SO_SNDBUF and SO_RCVBUF socket 
options.

rds_sendmsg (net/rds/send.c) checks this limit a bit later (after 
rds_message_alloc()):
         while (!rds_send_queue_rm(rs, conn, rm, rs->rs_bound_port,
                                   dport, &queued)) {
                 rds_stats_inc(s_send_queue_full);
                 /* XXX make sure this is reasonable */
                 if (payload_len > rds_sk_sndbuf(rs)) {
                         ret = -EMSGSIZE;
                         goto out;
                 }
                 ....
Venkat