| Message ID | 20110630182513.GC18713@fieldses.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 06/30/2011 11:25 AM, J. Bruce Fields wrote: > On Mon, Jun 20, 2011 at 04:26:48PM -0700, Ben Greear wrote: >> On 06/20/2011 03:42 PM, Ben Greear wrote: >>> This machine is acting as a server. It is from linux-2.6, pulled >>> today: >>> >>> commit de505e709ffb09a7382ca8e0d8c7dbb171ba5830 >>> >>> We are hitting it with 200 clients reading and writing, mounting and >>> un-mounting. >>> This bug is fairly reproducible (twice today). >>> >>> Large amounts of debugging options are enabled. >> >> We were also starting/stopping NFS on the server machine. >> It appears that this crash happens during the >> /etc/init.d/nfs stop >> command. > > I'll be submitting the below. > > The bug's been there for a really long time and we're getting late into > the release cycle so I'll probably just save it for 3.1 (but it'll go to > stable as well then). Looks good to me! Thanks, Ben > > --b. > > commit 0f4bb2521a0e300443e9d80b10778f5a93cc0dbc > Author: J. Bruce Fields<bfields@redhat.com> > Date: Wed Jun 29 16:49:04 2011 -0400 > > svcrpc: fix list-corrupting race on nfsd shutdown > > 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: stable@kernel.org > Cc: gnb@fmeh.org > Reported-by: Ben Greear<greearb@candelatech.com> > Tested-by: Ben Greear<greearb@candelatech.com> > Signed-off-by: J. Bruce Fields<bfields@redhat.com> > > diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c > index ab86b79..bd31208 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);
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c index ab86b79..bd31208 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);