percpu: avoid calling __pcpu_ptr_to_addr(NULL)

__pcpu_ptr_to_addr() can be overridden by the architecture and might not
behave well if passed a NULL pointer.  So avoid calling it until we have
verified that its arg is not NULL.

Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/percpu.c b/mm/percpu.c
index 442010c..083e7c9 100644 (file)
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1271,7 +1271,7 @@ static void pcpu_reclaim(struct work_struct *work)
  */
 void free_percpu(void *ptr)
 {
-       void *addr = __pcpu_ptr_to_addr(ptr);
+       void *addr;
        struct pcpu_chunk *chunk;
        unsigned long flags;
        int off;
@@ -1279,6 +1279,8 @@ void free_percpu(void *ptr)
        if (!ptr)
                return;
 
+       addr = __pcpu_ptr_to_addr(ptr);
+
        spin_lock_irqsave(&pcpu_lock, flags);
 
        chunk = pcpu_chunk_addr_search(addr);