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authorJ. Bruce Fields <bfields@redhat.com>2011-06-29 16:49:04 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2011-08-08 10:23:13 -0700
commit8a8b5c1b6f911444c0623b991cde497df64cb84c (patch)
treed761d03ce4d28deecd37ec37ee1592f8b72c86f2
parent98aea907860bce247af40351a297d56ef44d7f26 (diff)
downloadlwn-8a8b5c1b6f911444c0623b991cde497df64cb84c.tar.gz
lwn-8a8b5c1b6f911444c0623b991cde497df64cb84c.zip
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 <greearb@candelatech.com> Tested-by: Ben Greear <greearb@candelatech.com> Signed-off-by: J. Bruce Fields <bfields@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--net/sunrpc/svc_xprt.c11
1 files changed, 6 insertions, 5 deletions
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index df760adaa2c9..cc1fb3655ad1 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -896,12 +896,13 @@ 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--;