Date: Tue, 1 Dec 2020 16:23:59 +0000 (UTC) From: Kristof Provost <kp@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r368237 - head/sys/net Message-ID: <202012011623.0B1GNx7c081663@repo.freebsd.org>
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Author: kp Date: Tue Dec 1 16:23:59 2020 New Revision: 368237 URL: https://svnweb.freebsd.org/changeset/base/368237 Log: if: Fix panic when destroying vnet and epair simultaneously When destroying a vnet and an epair (with one end in the vnet) we often panicked. This was the result of the destruction of the epair, which destroys both ends simultaneously, happening while vnet_if_return() was moving the struct ifnet to its home vnet. This can result in a freed ifnet being re-added to the home vnet V_ifnet list. That in turn panics the next time the ifnet is used. Prevent this race by ensuring that vnet_if_return() cannot run at the same time as if_detach() or epair_clone_destroy(). PR: 238870, 234985, 244703, 250870 MFC after: 2 weeks Sponsored by: Modirum MDPay Differential Revision: https://reviews.freebsd.org/D27378 Modified: head/sys/net/if.c Modified: head/sys/net/if.c ============================================================================== --- head/sys/net/if.c Tue Dec 1 16:06:31 2020 (r368236) +++ head/sys/net/if.c Tue Dec 1 16:23:59 2020 (r368237) @@ -314,6 +314,9 @@ VNET_DEFINE(struct ifnet **, ifindex_table); struct sx ifnet_sxlock; SX_SYSINIT_FLAGS(ifnet_sx, &ifnet_sxlock, "ifnet_sx", SX_RECURSE); +struct sx ifnet_detach_sxlock; +SX_SYSINIT(ifnet_detach, &ifnet_detach_sxlock, "ifnet_detach_sx"); + /* * The allocation of network interfaces is a rather non-atomic affair; we * need to select an index before we are ready to expose the interface for @@ -543,7 +546,9 @@ vnet_if_return(const void *unused __unused) IFNET_WUNLOCK(); for (int j = 0; j < i; j++) { + sx_xlock(&ifnet_detach_sxlock); if_vmove(pending[j], pending[j]->if_home_vnet); + sx_xunlock(&ifnet_detach_sxlock); } free(pending, M_IFNET); @@ -1118,8 +1123,11 @@ if_detach(struct ifnet *ifp) CURVNET_SET_QUIET(ifp->if_vnet); found = if_unlink_ifnet(ifp, false); - if (found) + if (found) { + sx_slock(&ifnet_detach_sxlock); if_detach_internal(ifp, 0, NULL); + sx_sunlock(&ifnet_detach_sxlock); + } CURVNET_RESTORE(); } @@ -3010,8 +3018,12 @@ ifioctl(struct socket *so, u_long cmd, caddr_t data, s goto out_noref; case SIOCIFDESTROY: error = priv_check(td, PRIV_NET_IFDESTROY); - if (error == 0) + + if (error == 0) { + sx_slock(&ifnet_detach_sxlock); error = if_clone_destroy(ifr->ifr_name); + sx_sunlock(&ifnet_detach_sxlock); + } goto out_noref; case SIOCIFGCLONERS:
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