resource: fix locking in find_next_iomem_res()

Since resources can be removed, locking should ensure that the resource
is not removed while accessing it.  However, find_next_iomem_res() does
not hold the lock while copying the data of the resource.

Keep holding the lock while the data is copied.  While at it, change the
return value to a more informative value.  It is disregarded by the
callers.

[akpm@linux-foundation.org: fix find_next_iomem_res() documentation]
Link: http://lkml.kernel.org/r/20190613045903.4922-2-namit@vmware.com
Fixes: ff3cc952d3f00 ("resource: Add remove_resource interface")
Signed-off-by: Nadav Amit <namit@vmware.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/resource.c b/kernel/resource.c
index d22423e85cf801ba358581f08390041c0929a2cf..3ced0cd45bdd5132d21c72c2121d04cc848646dd 100644 (file)
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -326,7 +326,7 @@ EXPORT_SYMBOL(release_resource);
  *
  * If a resource is found, returns 0 and @*res is overwritten with the part
  * of the resource that's within [@start..@end]; if none is found, returns
- * -1 or -EINVAL for other invalid parameters.
+ * -ENODEV.  Returns -EINVAL for invalid parameters.
  *
  * This function walks the whole tree and not just first level children
  * unless @first_lvl is true.
@@ -365,16 +365,16 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
                        break;
        }
 
+       if (p) {
+               /* copy data */
+               res->start = max(start, p->start);
+               res->end = min(end, p->end);
+               res->flags = p->flags;
+               res->desc = p->desc;
+       }
+
        read_unlock(&resource_lock);
-       if (!p)
-               return -1;
-
-       /* copy data */
-       res->start = max(start, p->start);
-       res->end = min(end, p->end);
-       res->flags = p->flags;
-       res->desc = p->desc;
-       return 0;
+       return p ? 0 : -ENODEV;
 }
 
 static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,