From 0b9c55355f283356e7d767098ebe074f15acd021 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 commit 15b87d67ff3dc042bee42f991858d6b121b3b3ca upstream. 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 Signed-off-by: Greg Kroah-Hartman --- 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 8be12d6d5e73..8e08d71df104 100644 --- a/drivers/misc/sgi-xp/xpc_uv.c +++ b/drivers/misc/sgi-xp/xpc_uv.c @@ -965,11 +965,13 @@ 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