Eric Lee / linux-smarc-t335x-v3.2

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Commit f797d9881b62c2ddb1d2e7bd80d87141949c84aa

Authored by Shaun Ruffell
Committed by Joerg Roedel
1 parent 55639353a0
Exists in master and in 4 other branches v3.2_AM335xPSP_04.06.00.11, v3.2_NEWT335xPSP_04.06.00.11, v3.2_SBC_SMARTMEN, v3.2_SMARCT335xPSP_04.06.00.11

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>

Showing 1 changed file with 5 additions and 0 deletions Side-by-side Diff

... ... @@ -676,6 +676,8 @@
676 676 struct device *dev = data;
677 677 int count;
678 678  
  679 + if (global_disable)
  680 + return;
679 681  
680 682 switch (action) {
681 683 case BUS_NOTIFY_UNBOUND_DRIVER:
... ... @@ -696,6 +698,9 @@
696 698 void dma_debug_add_bus(struct bus_type *bus)
697 699 {
698 700 struct notifier_block *nb;
  701 +
  702 + if (global_disable)
  703 + return;
699 704  
700 705 nb = kzalloc(sizeof(struct notifier_block), GFP_KERNEL);
701 706 if (nb == NULL) {