dma-mapping: avoid oops when parameter cpu_addr is null

To keep consistent with kfree, which tolerate ptr is NULL.  We do this
because sometimes we may use goto statement, so that success and failure
case can share parts of the code.  But unfortunately, dma_free_coherent
called with parameter cpu_addr is null will cause oops, such as showed
below:

  Unable to handle kernel paging request at virtual address ffffffc020d3b2b8
  pgd = ffffffc083a61000
  [ffffffc020d3b2b8] *pgd=0000000000000000, *pud=0000000000000000
  CPU: 4 PID: 1489 Comm: malloc_dma_1 Tainted: G           O    4.1.12 #1
  Hardware name: ARM64 (DT)
  PC is at __dma_free_coherent.isra.10+0x74/0xc8
  LR is at __dma_free+0x9c/0xb0
  Process malloc_dma_1 (pid: 1489, stack limit = 0xffffffc0837fc020)
  [...]
  Call trace:
    __dma_free_coherent.isra.10+0x74/0xc8
    __dma_free+0x9c/0xb0
    malloc_dma+0x104/0x158 [dma_alloc_coherent_mtmalloc]
    kthread+0xec/0xfc

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 75857cda38e989e5a44150c5abb9bd1bd4872957..728ef074602a69d6046e6ff68f10ea84bdc172cd 100644 (file)
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -386,7 +386,7 @@ static inline void dma_free_attrs(struct device *dev, size_t size,
        if (dma_release_from_coherent(dev, get_order(size), cpu_addr))
                return;
 
-       if (!ops->free)
+       if (!ops->free || !cpu_addr)
                return;
 
        debug_dma_free_coherent(dev, size, cpu_addr, dma_handle);