From: J. Bruce Fields Date: Wed, 29 Jun 2011 20:49:04 +0000 (-0400) Subject: svcrpc: fix list-corrupting race on nfsd shutdown X-Git-Tag: firefly_0821_release~7541^2~3047 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=83d20a07d3fc171d5d7cddb6ebe2cd7a5fee1047;p=firefly-linux-kernel-4.4.55.git svcrpc: fix list-corrupting race on nfsd shutdown commit ebc63e531cc6a457595dd110b07ac530eae788c3 upstream. After commit 3262c816a3d7fb1eaabce633caa317887ed549ae "[PATCH] knfsd: split svc_serv into pools", svc_delete_xprt (then svc_delete_socket) no longer removed its xpt_ready (then sk_ready) field from whatever list it was on, noting that there was no point since the whole list was about to be destroyed anyway. That was mostly true, but forgot that a few svc_xprt_enqueue()'s might still be hanging around playing with the about-to-be-destroyed list, and could get themselves into trouble writing to freed memory if we left this xprt on the list after freeing it. (This is actually functionally identical to a patch made first by Ben Greear, but with more comments.) Cc: gnb@fmeh.org Reported-by: Ben Greear Tested-by: Ben Greear Signed-off-by: J. Bruce Fields Signed-off-by: Greg Kroah-Hartman --- diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c index ab86b7927f84..bd31208bbb61 100644 --- a/net/sunrpc/svc_xprt.c +++ b/net/sunrpc/svc_xprt.c @@ -902,12 +902,13 @@ void svc_delete_xprt(struct svc_xprt *xprt) if (!test_and_set_bit(XPT_DETACHED, &xprt->xpt_flags)) list_del_init(&xprt->xpt_list); /* - * We used to delete the transport from whichever list - * it's sk_xprt.xpt_ready node was on, but we don't actually - * need to. This is because the only time we're called - * while still attached to a queue, the queue itself - * is about to be destroyed (in svc_destroy). + * The only time we're called while xpt_ready is still on a list + * is while the list itself is about to be destroyed (in + * svc_destroy). BUT svc_xprt_enqueue could still be attempting + * to add new entries to the sp_sockets list, so we can't leave + * a freed xprt on it. */ + list_del_init(&xprt->xpt_ready); if (test_bit(XPT_TEMP, &xprt->xpt_flags)) serv->sv_tmpcnt--; spin_unlock_bh(&serv->sv_lock);