Date: Fri, 30 Nov 2018 10:36:14 +0000 (UTC) From: "Andrey V. Elsukov" <ae@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r341334 - head/sys/net Message-ID: <201811301036.wAUAaE9c094059@repo.freebsd.org>
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Author: ae Date: Fri Nov 30 10:36:14 2018 New Revision: 341334 URL: https://svnweb.freebsd.org/changeset/base/341334 Log: Adapt the fix in r341008 to correctly work with EBR. IFNET_RLOCK_NOSLEEP() is epoch_enter_preempt() in FreeBSD 12+. Holding it in sysctl_rtsock() doesn't protect us from ifnet unlinking, because unlinking occurs with IFNET_WLOCK(), that is rw_wlock+sx_xlock, and it doesn check that concurrent code is running in epoch section. But while we are in epoch section, we should be able to do access to ifnet's fields, even it was unlinked. Thus do not change if_addr and if_hw_addr fields in ifnet_detach_internal() to NULL, since rtsock code can do access to these fields and this is allowed while it is running in epoch section. This should fix the race, when ifnet_detach_internal() unlinks ifnet after we checked it for IFF_DYING in sysctl_dumpentry. Move free(ifp->if_hw_addr) into ifnet_free_internal(). Also remove the NULL check for ifp->if_description, since free(9) can correctly handle NULL pointer. MFC after: 1 week Modified: head/sys/net/if.c Modified: head/sys/net/if.c ============================================================================== --- head/sys/net/if.c Fri Nov 30 10:31:30 2018 (r341333) +++ head/sys/net/if.c Fri Nov 30 10:36:14 2018 (r341334) @@ -597,8 +597,6 @@ if_free_internal(struct ifnet *ifp) #ifdef MAC mac_ifnet_destroy(ifp); #endif /* MAC */ - if (ifp->if_description != NULL) - free(ifp->if_description, M_IFDESCR); IF_AFDATA_DESTROY(ifp); IF_ADDR_LOCK_DESTROY(ifp); ifq_delete(&ifp->if_snd); @@ -606,6 +604,8 @@ if_free_internal(struct ifnet *ifp) for (int i = 0; i < IFCOUNTERS; i++) counter_u64_free(ifp->if_counters[i]); + free(ifp->if_description, M_IFDESCR); + free(ifp->if_hw_addr, M_IFADDR); free(ifp, M_IFNET); } @@ -1184,14 +1184,8 @@ if_detach_internal(struct ifnet *ifp, int vmove, struc if_dead(ifp); /* - * Remove link ifaddr pointer and maybe decrement if_index. * Clean up all addresses. */ - free(ifp->if_hw_addr, M_IFADDR); - ifp->if_hw_addr = NULL; - ifp->if_addr = NULL; - - /* We can now free link ifaddr. */ IF_ADDR_WLOCK(ifp); if (!CK_STAILQ_EMPTY(&ifp->if_addrhead)) { ifa = CK_STAILQ_FIRST(&ifp->if_addrhead);
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