svcrpc: fix list-corrupting race on nfsd shutdown
After commit 3262c816a3
"[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>
This commit is contained in:
parent
058c5c9999
commit
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@ -902,12 +902,13 @@ void svc_delete_xprt(struct svc_xprt *xprt)
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if (!test_and_set_bit(XPT_DETACHED, &xprt->xpt_flags))
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list_del_init(&xprt->xpt_list);
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/*
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* We used to delete the transport from whichever list
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* it's sk_xprt.xpt_ready node was on, but we don't actually
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* need to. This is because the only time we're called
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* while still attached to a queue, the queue itself
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* is about to be destroyed (in svc_destroy).
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* The only time we're called while xpt_ready is still on a list
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* is while the list itself is about to be destroyed (in
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* svc_destroy). BUT svc_xprt_enqueue could still be attempting
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* to add new entries to the sp_sockets list, so we can't leave
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* a freed xprt on it.
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*/
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list_del_init(&xprt->xpt_ready);
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if (test_bit(XPT_TEMP, &xprt->xpt_flags))
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serv->sv_tmpcnt--;
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spin_unlock_bh(&serv->sv_lock);
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