Messages in this thread Patch in this message | | | From | Andi Kleen <> | Subject | [PATCH] [23/50] svcrpc: fix list-corrupting race on nfsd shutdown | Date | Thu, 28 Jul 2011 16:44:27 -0700 (PDT) |
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2.6.35-longterm review patch. If anyone has any objections, please let me know.
------------------ From: J. Bruce Fields <bfields@redhat.com>
[ upstream commit ebc63e531cc6a457595dd110b07ac530eae788c3 ]
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> Signed-off-by: Andi Kleen <ak@linux.intel.com>
Index: linux-2.6.35.y/net/sunrpc/svc_xprt.c =================================================================== --- linux-2.6.35.y.orig/net/sunrpc/svc_xprt.c +++ linux-2.6.35.y/net/sunrpc/svc_xprt.c @@ -894,12 +894,13 @@ void svc_delete_xprt(struct svc_xprt *xp 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);
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