Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1332286

Re: Bug 4.1.16: self-detected stall in net/unix/?

Show all headers | View raw

Rainer Weikusat <rw@doppelsaurus.mobileactivedefense.com> writes:
> Ben Hutchings <ben@decadent.org.uk> writes:

[...]

>> unix: Fix potential double-unlock in unix_dgram_sendmsg()
>>
>> A datagram socket may be peered with itself, so that sk == other.  We
>> use unix_state_double_lock() to lock sk and other in the right order,
>> which also guards against this and only locks the socket once, but we
>> then end up trying to unlock it twice.  Add the check for sk != other.

[...]

> other was found via
>
> 	if (!other) {
> 		err = -ECONNRESET;
> 		if (sunaddr == NULL)
> 			goto out_free;
>
> 		other = unix_find_other(net, sunaddr, namelen, sk->sk_type,
> 					hash, &err);
> 		if (other == NULL)
> 			goto out_free;
> 	}
>
> and the if-block leading to the double lock should never have been
> executed as it's supposed to deal with the case where sk is connect to
> other but other not to sk (eg, /dev/log).

Test program triggering a double unlock (w/o the MSG_DONTWAIT, it blocks
which it isn't supposed to do):

--------
#include <stdio.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>

#define SUN_NAME	"\0other-is-me"

int main(int argc, char **argv)
{
    struct sockaddr_un sun;
    unsigned max;
    int sk, rc;

    sk = socket(AF_UNIX, SOCK_DGRAM, 0);

    sun.sun_family = AF_UNIX;
    strncpy(sun.sun_path, SUN_NAME, sizeof(sun.sun_path));
    bind(sk, (struct sockaddr *)&sun, sizeof(sun));

    max = 12;
    do 
	sendto(sk, &sun, sizeof(sun), MSG_DONTWAIT,
	       (struct sockaddr *)&sun, sizeof(sun));
    while (--max);

    return 0;
}

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Re: Bug 4.1.16: self-detected stall in net/unix/? Philipp Hahn <pmhahn@pmhahn.de> - 2016-02-11 14:50 +0100
  Re: Bug 4.1.16: self-detected stall in net/unix/? Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2016-02-11 17:00 +0100
    Re: Bug 4.1.16: self-detected stall in net/unix/? Ben Hutchings <ben@decadent.org.uk> - 2016-02-11 18:10 +0100
      Re: Bug 4.1.16: self-detected stall in net/unix/? Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2016-02-11 18:50 +0100
        Re: Bug 4.1.16: self-detected stall in net/unix/? Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2016-02-11 19:00 +0100
        Re: Bug 4.1.16: self-detected stall in net/unix/? Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2016-02-11 19:40 +0100
          [PATCH net] af_unix: Guard against other == sk in unix_dgram_sendmsg Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2016-02-11 20:40 +0100
            Re: [PATCH net] af_unix: Guard against other == sk in  unix_dgram_sendmsg Philipp Hahn <pmhahn@pmhahn.de> - 2016-02-12 10:20 +0100
              Re: [PATCH net] af_unix: Guard against other == sk in unix_dgram_sendmsg Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2016-02-12 14:30 +0100
                Re: [PATCH net] af_unix: Guard against other == sk in  unix_dgram_sendmsg Ben Hutchings <ben@decadent.org.uk> - 2016-02-12 21:00 +0100
                Re: [PATCH net] af_unix: Guard against other == sk in unix_dgram_sendmsg Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2016-02-12 21:20 +0100
                Re: [PATCH net] af_unix: Guard against other == sk in  unix_dgram_sendmsg Ben Hutchings <ben@decadent.org.uk> - 2016-02-12 21:50 +0100
                Re: [PATCH net] af_unix: Guard against other == sk in unix_dgram_sendmsg Rainer Weikusat <rweikusat@mobileactivedefense.com> - 2016-02-12 22:10 +0100
            Re: [PATCH net] af_unix: Guard against other == sk in  unix_dgram_sendmsg David Miller <davem@davemloft.net> - 2016-02-16 19:00 +0100

csiph-web