linux-kernel - [for-next][PATCH 02/12] tracepoint: Use struct

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Date:   Tue, 25 Jun 2019 15:15:12 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [for-next][PATCH 02/12] tracepoint: Use struct_size() in kmalloc()

From: "Gustavo A. R. Silva" <gustavo@...eddedor.com>

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 tp_probes {
	...
        struct tracepoint_func probes[0];
};

instance = kmalloc(sizeof(sizeof(struct tp_probes) +
			sizeof(struct tracepoint_func) * count, GFP_KERNEL);

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

instance = kmalloc(struct_size(instance, probes, count) GFP_KERNEL);

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 kernel/tracepoint.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 46f2ab1e08a9..fb9353ed901b 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -68,8 +68,8 @@ struct tp_probes {
 
 static inline void *allocate_probes(int count)
 {
-	struct tp_probes *p  = kmalloc(count * sizeof(struct tracepoint_func)
-			+ sizeof(struct tp_probes), GFP_KERNEL);
+	struct tp_probes *p  = kmalloc(struct_size(p, probes, count),
+				       GFP_KERNEL);
 	return p == NULL ? NULL : p->probes;
 }
 
-- 
2.20.1