[tip:x86/cleanups] x86/kexec/crash: Use struct_size() in vzalloc()

["tip-bot for Gustavo A. R. Silva" <tipbot@zytor.com>]

Commit-ID:  4df4309587e18a3c91e68138638dcb9d2a968906
Gitweb:     https://git.kernel.org/tip/4df4309587e18a3c91e68138638dcb9d2a968906
Author:     Gustavo A. R. Silva <gustavo@embeddedor.com>
AuthorDate: Wed, 3 Apr 2019 13:42:30 -0500
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 5 Apr 2019 13:18:38 +0200

x86/kexec/crash: Use struct_size() in vzalloc()

One of the more common cases of allocation size calculations is finding the
size of a structure that has a zero-sized array at the end, along with
memory for some number of elements for that array. For example:

struct foo {
    int stuff;
    struct boo entry[];
};

instance = vzalloc(sizeof(struct foo) + count * sizeof(struct boo));

Instead of leaving these open-coded and prone to type mistakes, use the new
struct_size() helper:

   instance = vzalloc(struct_size(instance, entry, count));

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lkml.kernel.org/r/20190403184230.GA5295@embeddedor
---
 arch/x86/kernel/crash.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 17ffc869cab8..a96ca8584803 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -204,8 +204,7 @@ static struct crash_mem *fill_up_crash_elf_data(void)
 	 * another range split. So add extra two slots here.
 	 */
 	nr_ranges += 2;
-	cmem = vzalloc(sizeof(struct crash_mem) +
-			sizeof(struct crash_mem_range) * nr_ranges);
+	cmem = vzalloc(struct_size(cmem, ranges, nr_ranges));
 	if (!cmem)
 		return NULL;