From 93326685f124a1b2a71843b1c41328be13f97bbb Mon Sep 17 00:00:00 2001 From: Roger Pau Monne Date: Wed, 31 Jul 2013 17:00:42 +0200 Subject: [PATCH] xen-gnt: prevent adding duplicate gnt callbacks MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit commit 5f338d9001094a56cf87bd8a280b4e7ff953bb59 upstream. With the current implementation, the callback in the tail of the list can be added twice, because the check done in gnttab_request_free_callback is bogus, callback->next can be NULL if it is the last callback in the list. If we add the same callback twice we end up with an infinite loop, were callback == callback->next. Replace this check with a proper one that iterates over the list to see if the callback has already been added. Signed-off-by: Roger Pau Monné Cc: Konrad Rzeszutek Wilk Cc: David Vrabel Signed-off-by: Konrad Rzeszutek Wilk Acked-by: Matt Wilson Reviewed-by: David Vrabel Signed-off-by: Greg Kroah-Hartman --- drivers/xen/grant-table.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c index 04c1b2d..d5418c1 100644 --- a/drivers/xen/grant-table.c +++ b/drivers/xen/grant-table.c @@ -729,9 +729,18 @@ void gnttab_request_free_callback(struct gnttab_free_callback *callback, void (*fn)(void *), void *arg, u16 count) { unsigned long flags; + struct gnttab_free_callback *cb; + spin_lock_irqsave(&gnttab_list_lock, flags); - if (callback->next) - goto out; + + /* Check if the callback is already on the list */ + cb = gnttab_free_callback_list; + while (cb) { + if (cb == callback) + goto out; + cb = cb->next; + } + callback->fn = fn; callback->arg = arg; callback->count = count; -- 2.7.4