svn commit: r278729 - head/sys/sys
hiren panchasara
hiren at strugglingcoder.info
Fri Feb 17 19:12:27 UTC 2017
On 03/19/15 at 11:08P, hiren panchasara wrote:
> On 03/16/15 at 06:06P, hiren panchasara wrote:
> > On 03/16/15 at 03:39P, Gleb Smirnoff wrote:
> > > On Wed, Mar 11, 2015 at 02:36:07PM -0700, hiren panchasara wrote:
> > > h> On 02/13/15 at 11:19P, Simon J. Gerraty wrote:
> > > h> > Author: sjg
> > > h> > Date: Fri Feb 13 23:19:35 2015
> > > h> > New Revision: 278729
> > > h> > URL: https://svnweb.freebsd.org/changeset/base/278729
> > > h> >
> > > h> > Log:
> > > h> > sbspace: size of bleft, mleft must match sockbuf fields to avoid
> > > h> > overflow on amd64
> > > h> >
> > > h> > Submitted by: anshukla at juniper.net
> > > h> > Obtained from: Juniper Networks
> > > h>
> > > h> Talking to sjg on -arch to MFC this. If he cannot get around doing that,
> > > h> I'll do it tomorrow.
> > > h>
> > > h> Letting people know here to see if there are any objections.
> > >
> > > Would that fix the bug we've been discussing?
> >
> > Unsure as I am not sure what caused the issue I saw.
> >
> > For those who do not know the details, we recently saw a userland
> > process stuck spinning at 100% around sbcut_internal(). Inside
> > sbflush_internal(), the sb_cc was grown to be about 4G. And before
> > passing it to sbcut_internal(), we cast it from uint to int which
> > would make that valud -ve.
> >
> > Gleb pointed out to me that sbspace() is supposed to check/stop sb_cc
> > from growing that large.
> >
> > Now, I am not sure if we'd ever run into this situation again but
> > current fix is a great catch anyways.
> >
> > I still have 2 questions around what we saw. It'd be great if someone can
> > clarify them for my understanding:
> >
> > 1) Even if we get into such a scenario that we were in, following would
> > help by not looping endlessly.
> >
> > --- uipc_sockbuf.c.0 2015-03-11 15:49:52.000000000 -0700
> > +++ uipc_sockbuf.c 2015-03-11 15:51:48.000000000 -0700
> > @@ -877,6 +877,9 @@
> > {
> > struct mbuf *m, *n, *next, *mfree;
> >
> > + if (len < 0)
> > + panic("%s: len is %d and it is supposed to be +ve",
> > + __func__, len);
> > +
> > next = (m = sb->sb_mb) ? m->m_nextpkt : 0;
> > mfree = NULL
> >
> > 2) We need 1) because we are casting a uint to int which _may_ rander a
> > value -ve. Is there a way we can avoid the casting?
>
> It'd be useful if someone with knowledge in this area can weigh in.
Ran into this again today. While the real question of how sb_ccc grew
this large is still unsolved, any objection to adding this patch to
avoid a hang and panic instead?
Cheers,
Hiren
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 603 bytes
Desc: not available
URL: <http://lists.freebsd.org/pipermail/svn-src-all/attachments/20170217/8cb96315/attachment.sig>
More information about the svn-src-all
mailing list