[PATCH] ARC: unwind: Use struct_size helper instead of open-coded arithmetic

[Len Baker <len.baker@gmx.com>]

Dynamic size calculations (especially multiplication) should not be
performed in memory allocator function arguments due to the risk of them
overflowing. This could lead to values wrapping around and a smaller
allocation being made than the caller was expecting. Using those
allocations could lead to linear overflows of heap memory and other
misbehaviors.

To avoid this scenario, use the struct_size helper.

Signed-off-by: Len Baker <len.baker@gmx.com>
---
 arch/arc/kernel/unwind.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/arc/kernel/unwind.c b/arch/arc/kernel/unwind.c
index 47bab67f8649..af18052b86a7 100644
--- a/arch/arc/kernel/unwind.c
+++ b/arch/arc/kernel/unwind.c
@@ -13,6 +13,7 @@
 #include <linux/sched.h>
 #include <linux/module.h>
 #include <linux/memblock.h>
+#include <linux/overflow.h>
 #include <linux/sort.h>
 #include <linux/slab.h>
 #include <linux/stop_machine.h>
@@ -312,9 +313,7 @@ static void init_unwind_hdr(struct unwind_table *table,
 	if (tableSize || !n)
 		goto ret_err;

-	hdrSize = 4 + sizeof(unsigned long) + sizeof(unsigned int)
-	    + 2 * n * sizeof(unsigned long);
-
+	hdrSize = struct_size(header, table, n);
 	header = alloc(hdrSize);
 	if (!header)
 		goto ret_err;
--
2.25.1