[PATCH 3.13 033/120] lib/genalloc.c: add check gen_pool_dma_alloc() if dma pointer is not NULL

[Greg Kroah-Hartman]

3.13-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "Lad, Prabhakar" <prabhakar.csengg@xxxxxxxxx>

commit 0368dfd01ae3b7647ef9b2f0525fdefd5e0d28e1 upstream.

In the gen_pool_dma_alloc() the dma pointer can be NULL and while
assigning gen_pool_virt_to_phys(pool, vaddr) to dma caused the following
crash on da850 evm:

   Unable to handle kernel NULL pointer dereference at virtual address 00000000
   Internal error: Oops: 805 [#1] PREEMPT ARM
   Modules linked in:
   CPU: 0 PID: 1 Comm: swapper Tainted: G        W    3.13.0-rc1-00001-g0609e45-dirty #5
   task: c4830000 ti: c4832000 task.ti: c4832000
   PC is at gen_pool_dma_alloc+0x30/0x3c
   LR is at gen_pool_virt_to_phys+0x74/0x80
   Process swapper, call trace:
     gen_pool_dma_alloc+0x30/0x3c
     davinci_pm_probe+0x40/0xa8
     platform_drv_probe+0x1c/0x4c
     driver_probe_device+0x98/0x22c
     __driver_attach+0x8c/0x90
     bus_for_each_dev+0x6c/0x8c
     bus_add_driver+0x124/0x1d4
     driver_register+0x78/0xf8
     platform_driver_probe+0x20/0xa4
     davinci_init_late+0xc/0x14
     init_machine_late+0x1c/0x28
     do_one_initcall+0x34/0x15c
     kernel_init_freeable+0xe4/0x1ac
     kernel_init+0x8/0xec

This patch fixes the above.

[akpm@xxxxxxxxxxxxxxxxxxxx: update kerneldoc]
Signed-off-by: Lad, Prabhakar <prabhakar.csengg@xxxxxxxxx>
Cc: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
Cc: Nicolin Chen <b42378@xxxxxxxxxxxxx>
Cc: Joe Perches <joe@xxxxxxxxxxx>
Cc: Sachin Kamat <sachin.kamat@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 lib/genalloc.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/lib/genalloc.c
+++ b/lib/genalloc.c
@@ -316,7 +316,7 @@ EXPORT_SYMBOL(gen_pool_alloc);
  * gen_pool_dma_alloc - allocate special memory from the pool for DMA usage
  * @pool: pool to allocate from
  * @size: number of bytes to allocate from the pool
- * @dma: dma-view physical address
+ * @dma: dma-view physical address return value.  Use NULL if unneeded.
  *
  * Allocate the requested number of bytes from the specified pool.
  * Uses the pool allocation function (with first-fit algorithm by default).
@@ -334,7 +334,8 @@ void *gen_pool_dma_alloc(struct gen_pool
 	if (!vaddr)
 		return NULL;
 
-	*dma = gen_pool_virt_to_phys(pool, vaddr);
+	if (dma)
+		*dma = gen_pool_virt_to_phys(pool, vaddr);
 
 	return (void *)vaddr;
 }


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