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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: [<c0580d35>] 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 <sruffell@digium.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
This commit is contained in:
Shaun Ruffell 2009-12-17 18:00:36 -06:00 committed by Joerg Roedel
parent 55639353a0
commit f797d9881b
1 changed files with 5 additions and 0 deletions
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5
lib/dma-debug.c
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@ -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");