From 15b87d67ff3dc042bee42f991858d6b121b3b3ca Mon Sep 17 00:00:00 2001 From: Robin Holt Date: Tue, 15 Dec 2009 16:47:57 -0800 Subject: [PATCH] x86: uv: xpc NULL deref when mesq becomes empty Under heavy load conditions, our set of xpc messages may become exhausted. The code handles this correctly with the exception of the management code which hits a NULL pointer dereference. Signed-off-by: Robin Holt Cc: Jack Steiner Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/misc/sgi-xp/xpc_uv.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/misc/sgi-xp/xpc_uv.c b/drivers/misc/sgi-xp/xpc_uv.c index bbf0e2ee6fd..19bd7b0ede9 100644 --- a/drivers/misc/sgi-xp/xpc_uv.c +++ b/drivers/misc/sgi-xp/xpc_uv.c @@ -949,11 +949,13 @@ xpc_get_fifo_entry_uv(struct xpc_fifo_head_uv *head) head->first = first->next; if (head->first == NULL) head->last = NULL; + + head->n_entries--; + BUG_ON(head->n_entries < 0); + + first->next = NULL; } - head->n_entries--; - BUG_ON(head->n_entries < 0); spin_unlock_irqrestore(&head->lock, irq_flags); - first->next = NULL; return first; } -- 2.39.5