lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Fri, 22 Jun 2012 10:29:06 +0200
From:	Eric Dumazet <>
To:	Josh Hunt <>
Cc:	"" <>,
	"" <>,
	Debabrata Banerjee <>,
	"" <>,
	"" <>,
	"" <>,
	"" <>,
	"" <>,
	"" <>
Subject: Re: Bug in net/ipv6/ip6_fib.c:fib6_dump_table()

On Fri, 2012-06-22 at 01:49 -0500, Josh Hunt wrote:
> On 06/21/2012 03:27 PM, Eric Dumazet wrote:
> > On Thu, 2012-06-21 at 14:35 -0500, Josh Hunt wrote:
> > 
> >> Can anyone provide details of the crash which was intended to be fixed
> >> by 2bec5a369ee79576a3eea2c23863325089785a2c? With this patch in and
> >> doing concurrent adds/deletes and dumping the table via netlink causes
> >> duplicate entries to be reported. Reverting this patch causes those
> >> problems to go away. We can provide a more detailed test if that is
> >> needed, but so far our testing has been unable to reproduce the crash
> >> mentioned in the above commit with it reverted.
> > 
> > A mere revert wont be enough.
> > 
> > Looking at this code, it lacks proper synchronization
> > between tree updaters and tree walkers.
> > 
> > fib6_walker_lock rwlock is not enough to prevent races.
> > 
> > Are you willing to fix this yourself ?
> > 
> Looking through the code a bit more it seems like we would need to have
> a lock in fib6_walker_t to protect its contents. Mainly for when we
> update the pointers in fib6_del_route and fib6_repair_tree. Right now
> there is the fib6_walker_lock, but that appears to only be protecting
> the elements of the list, not their contents. Is this what you had in
> mind? I just coded up something along these lines and it works for the
> most part, but I also got a message about unsafe lock ordering when I
> stressed it so I am messing something up. If this sounds like it's on
> the right track I can work out the kinks in the morning.

Hmm, it seems tb6_lock is held by a writer, so its safe :

a tree walker can run only holding a read_lock on tb6_lock

To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to
More majordomo info at

Powered by blists - more mailing lists