From: Shaun Ruffell Date: Fri, 18 Dec 2009 00:00:36 +0000 (-0600) Subject: dma-debug: Do not add notifier when dma debugging is disabled. X-Git-Tag: v2.6.33-rc3~26^2~5^2~1 X-Git-Url: http://ftp.safe.ca/?p=safe%2Fjmp%2Flinux-2.6;a=commitdiff_plain;h=f797d9881b62c2ddb1d2e7bd80d87141949c84aa dma-debug: Do not add notifier when dma debugging is disabled. If CONFIG_HAVE_DMA_API_DEBUG is defined and "dma_debug=off" is specified on the kernel command line, when you detach a driver from a device you can cause the following NULL pointer dereference: BUG: unable to handle kernel NULL pointer dereference at (null) IP: [] dma_debug_device_change+0x5d/0x117 The problem is that the dma_debug_device_change notifier function is added to the bus notifier chain even though the dma_entry_hash array was never initialized. If dma debugging is disabled, this patch both prevents dma_debug_device_change notifiers from being added to the chain, and additionally ensures that the dma_debug_device_change notifier function is a no-op. Cc: stable@kernel.org Signed-off-by: Shaun Ruffell Signed-off-by: Joerg Roedel --- diff --git a/lib/dma-debug.c b/lib/dma-debug.c index d9b08e0..7399744 100644 --- a/lib/dma-debug.c +++ b/lib/dma-debug.c @@ -676,6 +676,8 @@ static int dma_debug_device_change(struct notifier_block *nb, struct device *dev = data; int count; + if (global_disable) + return; switch (action) { case BUS_NOTIFY_UNBOUND_DRIVER: @@ -697,6 +699,9 @@ void dma_debug_add_bus(struct bus_type *bus) { struct notifier_block *nb; + if (global_disable) + return; + nb = kzalloc(sizeof(struct notifier_block), GFP_KERNEL); if (nb == NULL) { pr_err("dma_debug_add_bus: out of memory\n");