Date: Mon, 22 Sep 2008 09:40:07 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: Norbert Papke <fbsd-ml@scrapper.ca>, lioux@FreeBSD.org Cc: stable@FreeBSD.org Subject: Possible UDP deadlock/panic fix Message-ID: <alpine.BSF.1.10.0809220937320.58772@fledge.watson.org>
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Attached is an MFC candidate for a patch I just merged to 8.x, which corrects
the UDP lock recursion issue both of you were running into. If it settles
well for a couple of days in HEAD then I'll go ahead and request an MFC from
re@, but your confirmation as to whether or not this corrects the specific
symptoms you are seeing would be very helpful. I was able to confirm that it
eliminated what appeared to be the same problem here when I attempted to
reproduce it based on the information you provided, so I'm hopeful.\
Thanks,
Robert N M Watson
Computer Laboratory
University of Cambridge
Property changes on: .
___________________________________________________________________
Modified: svn:mergeinfo
Merged /head/sys:r183265
Index: netinet6/udp6_usrreq.c
===================================================================
--- netinet6/udp6_usrreq.c (revision 183265)
+++ netinet6/udp6_usrreq.c (working copy)
@@ -975,13 +975,23 @@
error = EINVAL;
goto out;
}
+
+ /*
+ * XXXRW: We release UDP-layer locks before calling
+ * udp_send() in order to avoid recursion. However,
+ * this does mean there is a short window where inp's
+ * fields are unstable. Could this lead to a
+ * potential race in which the factors causing us to
+ * select the UDPv4 output routine are invalidated?
+ */
+ INP_WUNLOCK(inp);
+ INP_INFO_WUNLOCK(&udbinfo);
if (sin6)
in6_sin6_2_sin_in_sock(addr);
pru = inetsw[ip_protox[IPPROTO_UDP]].pr_usrreqs;
- error = ((*pru->pru_send)(so, flags, m, addr, control,
+ /* addr will just be freed in sendit(). */
+ return ((*pru->pru_send)(so, flags, m, addr, control,
td));
- /* addr will just be freed in sendit(). */
- goto out;
}
}
#endif
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